200923611 九、發明說明： 【發明所屬之技術領域】 本發明係有關於一種可調整溫度係數之參考電路，可 藉由調整第一電流源與第二電流源之電流差而改變參考電 壓及第三溫度係數，以得到一溫度係數穩定的參考電壓。 【先前技術】 可產生參考電壓之參考電路，被廣泛應用於偏壓電 路、調節器、類比數位及數位類比轉換器等等應用電路， 並且參考電路所產生的參考電壓必須與溫度相依性極低， 以避免溫度因素而影響到參考電壓的穩定性。 如第1圖所示’係為習用參考電路之電路結構圖。如 圖所示，習用參考電路之結構包括有一電流鏡電路U、一 可變電阻器13及一雙載子電晶體15，並且電流鏡電路η 依序串聯連接可變電阻器13及雙載子電晶體15。 電流鏡電路11可產生一電流Ιχ與一電流ιΡΤΑΤ，其中電 流IpTAT係為一與絕對溫度成正比(Proportional to Absolute Temperature; PTAT)之正溫度係數電流，並且與電流Ιχ成鏡 射的關係。電流ΙΡΤΑΤ流經電阻器13會產生一正溫度係數電 壓VPTAT’而流經雙載子電晶體(Q6)15則產生與絕對溫度成 反比（Counter Proportional to Absolute Temperature; CTAT) 的負溫度係數電壓VcrAT。 參考電路可藉由正溫度係數電壓VPTAT與負溫度係數電 壓VCTAT的總加而得到一參考電壓vREF，並且電壓vPTAT的 200923611 正溫度係數係可抵補電壓vCTAT的負溫度係數，以使得參考 H Vref之溫度係數能夠趨近於零溫度係數，如此以避免 參考電壓VREF隨著溫度係數的變化而產生劇烈的變動。 此外’電流鏡電路11可包括有電晶體Q卜Q2、Q3、 Q4、Q5及電阻器Rx，並且電流鏡電路丨丨之電晶體Q4與 電晶體Q5之面積比係為ι:ρ，而電流ΙρτΑΤ=ΡΙχ。因此，習 用參考電路可藉由調整電晶體Q4與電晶體Q5間的面積比 來決定電流ιΡΤΑΤ之電流大小，並進而改變參考電壓Vref 及其/皿度係數，如此將可調整出所需的參考電壓VREF。 【發明内容】 本^明之主要目的在於提出一種可調整溫度係數之參 考電路，參考電路可藉由調整第—電流源與第二電流源間 =電流差耐變所產生的參考電壓及其溫度錄，藉此以 得到一溫度係數穩定的參考電壓。 本發明之-欠要目的在於提出—種可調整溫度係數之參 考電路纟中參考電壓的溫度係數係為一可調整的溫度係 數，並根據應用電路對於溫度係數的應用需求而調整為零 溫度係數、正溫度係數及負溫度係數之其中之一者。 本發明之又-目的在於提出一種可調整溫度係數之參 考電路，參考電_可_輕第—參考單元及第二參考 早兀内半導航件的設置數量及其半導體元件的長寬比， :擴大參考電壓的電壓_，以設計出各種電壓準位的參 老雷懕。 200923611 本發明之又一目的在於提出一種可調整溫度係數之參 考電路，參考電路可藉由一可變電阻器之作用，而微調第 一電流源或第二電流源的電流值，藉此修正製程中因製程 偏移所產生的誤差，以調整出一正確的參考電壓及其溫度 係數。 為此，本發明提供一種可調整溫度係數之參考電路， 其主要結構係包括有：一第一電流源，其輸入端連接一供 應電壓；一第一參考單元，其一端連接該第一電流源之輸 出端於一第一節點，另一端接地；一第二參考單元，其一 端連接該第一電流源之輸出端於該第一節點；及一第二電 流源，其輸入端連接該第二參考單元之另一端於一第二節 點，其輸出端接地；其中，該第一參考單元具有一第一溫 度係數之第一加總電壓，該第二參考單元具有一第二溫度 係數之第二加總電壓；該第二節點具有一參考電壓，即為 該第一加總電壓與該第二加總電壓的電壓差，該參考電壓 具有一第三溫度係數，即為該第一溫度係數與該第二溫度 係數之差值。 本發明尚提供一種可調整溫度係數之參考電路，其主 要結構係包括有：一第一電流源，其輸出端接地；一第一 參考單元，其一端連接該第一電流源之輸入端於一第一節 點，另一端連接一供應電壓；一第二參考單元，其一端連 接該第一電流源之輸入端於一第一節點；及一第二電流 源，其輸出端連接該第二參考單元之另一端於一第二節 點，其輸入端連接該供應電壓；其中，該第一參考單元具 200923611 . 有一第一溫度係數之第一加總電壓，該第二參考單元具有 一第二溫度係數之第二加總電壓；該供應電壓與該第二節 點間具有一參考電壓，即為該第一加總電壓與該第二加總 電壓的電壓差，該參考電壓具有一第三溫度係數，即為該 第一溫度係數與該第二溫度係數之差值。 【實施方式】 首先，請參閱第2圖係為本發明參考電路一較佳實施 例之電路結構圖。如圖所示，參考電路之主要結構包括有 一第一電流源Ια、一第二電流源Ib、一第一參考單元21、 一第二參考單元23。第一電流源1八之輸入端連接供應電壓 VDD ;第一參考單元21之一端連接第一電流源1八之輸出端 於第一節點ISh，另一端接地；第二參考單元23之一端連接 第一電流源IA之輸出端於第一節點Ν!，另一端連接第二電 流源IB之輸入端於第二節點N2;而第二電流源IB之輸出端 接地。 I 其中，第一電流源IA與第二電流源IB間的電流差(IA-IB) 可偏壓於第一參考單元21，以使得第一參考單元21具有第 一溫度係數;5 之第一加總電壓Vpu)。第二電流源IB可偏 壓於第二參考單元23，以使得第二參考單元23具有一第二 溫度係數/3 (γι)的第二加總電壓V(yi)。 弟一加總電壓與第二加總電壓YI)間的電壓差 (V(XJ)_V(YI))即為第二節點N2上之參考電壓VreF ’即 VrefS^P^-V^y!)。該參考電壓Vref具有一第三溫度係數 200923611 VREF，該第三溫度係數y3REF為第一溫度係數y3(XJ)與第二溫 度係數(YI)間之差值’即；5 REF=卢(XJ)· (YI)。 本發明中第一電流源IA與第二電流源IB之其中之一者 係為可調式的電流源，因此可透過第一電流源IA或第二電 流源IB的調整而改變兩者間的電流差(IA-IB)，而使得第一參 考單元21及第二參考單元23間之電壓差值(V()U)-V(YI))與溫 度係數差值（/3 (xj)- y3 (γι))跟者改變。如此根據電壓差值 (V(yi))與溫度係數差值（yS (xj) - /S (γι))所求得的參考電 壓VREF及其第三溫度係數/3REF即可調整修正。 第一參考單元21包括有複數個串聯連接之半導體元件 211、212、213，各半導體元件211、212、213係為連接成 二極體形式的半導體元件，可分別選擇為一 P通道金氧半 電晶體、一 N通道金氧半電晶體、一 P型雙載子電晶體、 一 N型雙載子電晶體、一 P型接面場效電晶體、一 N型接 面場效電晶體、一 PN二極體、一齊納二極體及一蕭特基二 極體之其中之一者。 本實施例之第一參考單元21之半導體元件211、212、 213亦可選擇混搭的方式，使用不同類型的半導體元件組合 而成，例如：半導體元件211係為P通道金氧半電晶體、 半導體元件212係為PN二極體，而半導體元件213係為N 通道金氧半電晶體。每一半導體元件211、212、213皆具有 一接面電壓 VgS(XI)、Vd(xn-I)、V〇S(XN)及其相對應的溫度係 數/5 (XI)、万(XN-1)、万(XN)。 弟一電流源Ια與苐二電流源Ib間的電流差(Ia-Ib)可偏 200923611 參考單元21’以使得第—參考單元21具有第一溫 j數〜)之第-加總電壓V(XJ) ’第一加總電壓ν⑽係為 =導體元件2^2 13之接面電壓的總合，例如： 〇〇)、Vgs(x1)+."+Vd(xn i)+Vgs ⑽），而第一溫度係數万⑽ :為半導體元件2U、212、2U之溫度係數的總合，例如： °°广 6(χι)+·.·+/3(χν.ι)+/3(χν)。 Ο200923611 IX. Description of the Invention: [Technical Field] The present invention relates to a reference circuit capable of adjusting a temperature coefficient, which can change a reference voltage and a third by adjusting a current difference between a first current source and a second current source Temperature coefficient to obtain a reference voltage with a stable temperature coefficient. [Prior Art] A reference circuit capable of generating a reference voltage is widely used in application circuits such as a bias circuit, a regulator, an analog digital and a digital analog converter, and the reference voltage generated by the reference circuit must be temperature dependent. Low, to avoid temperature factors affecting the stability of the reference voltage. As shown in Fig. 1, it is a circuit configuration diagram of a conventional reference circuit. As shown in the figure, the structure of the conventional reference circuit includes a current mirror circuit U, a variable resistor 13 and a double carrier transistor 15, and the current mirror circuit η is connected in series with the variable resistor 13 and the double carrier. Transistor 15. The current mirror circuit 11 generates a current Ιχ and a current ΡΤΑΤ, wherein the current IpTAT is a positive temperature coefficient current proportional to absolute temperature (PTAT) and is mirrored in relation to the current. The current ΙΡΤΑΤ flows through the resistor 13 to generate a positive temperature coefficient voltage VPTAT' and flows through the bipolar transistor (Q6) 15 to generate a negative temperature coefficient voltage VcrAT that is inversely proportional to the absolute temperature (CTAT) (Counter Proportional to Absolute Temperature; CTAT) . The reference circuit can obtain a reference voltage vREF by adding the positive temperature coefficient voltage VPTAT and the negative temperature coefficient voltage VCTAT, and the 200923611 positive temperature coefficient of the voltage vPTAT can offset the negative temperature coefficient of the voltage vCTAT, so that the reference H Vref The temperature coefficient can approach the zero temperature coefficient, thus avoiding drastic changes in the reference voltage VREF as a function of the temperature coefficient. In addition, the current mirror circuit 11 may include a transistor Q Q2, Q3, Q4, Q5 and a resistor Rx, and the area ratio of the transistor Q4 to the transistor Q5 of the current mirror circuit is ι:ρ, and the current ΙρτΑΤ=ΡΙχ. Therefore, the conventional reference circuit can determine the current of the current ιΡΤΑΤ by adjusting the area ratio between the transistor Q4 and the transistor Q5, and then change the reference voltage Vref and/or the coefficient of the degree, so that the required reference can be adjusted. Voltage VREF. SUMMARY OF THE INVENTION The main purpose of the present invention is to provide a reference circuit capable of adjusting the temperature coefficient. The reference circuit can adjust the reference voltage generated by the resistance between the first current source and the second current source and the temperature difference. Thereby, a reference voltage having a stable temperature coefficient is obtained. The purpose of the present invention is to propose that the temperature coefficient of the reference voltage in the reference circuit of the adjustable temperature coefficient is an adjustable temperature coefficient, and is adjusted to the zero temperature coefficient according to the application requirement of the application circuit for the temperature coefficient. One of the positive temperature coefficient and the negative temperature coefficient. Still another object of the present invention is to provide a reference circuit capable of adjusting a temperature coefficient, with reference to the set number of the electric_light_reference unit and the second reference early half inner navigation member and the aspect ratio of the semiconductor element thereof, Expand the voltage _ of the reference voltage to design the old thunder of various voltage levels. 200923611 Another object of the present invention is to provide a reference circuit capable of adjusting a temperature coefficient, and the reference circuit can finely adjust the current value of the first current source or the second current source by a variable resistor, thereby correcting the process The error caused by the process offset is adjusted to adjust a correct reference voltage and its temperature coefficient. To this end, the present invention provides a reference circuit capable of adjusting a temperature coefficient, the main structure of which includes: a first current source having an input terminal connected to a supply voltage; and a first reference unit having one end connected to the first current source The output end is connected to the first node and the other end is grounded; a second reference unit has one end connected to the output end of the first current source to the first node; and a second current source whose input end is connected to the second The other end of the reference unit is connected to the second node, and the output end thereof is grounded; wherein the first reference unit has a first total voltage of a first temperature coefficient, and the second reference unit has a second second temperature coefficient Adding a total voltage; the second node has a reference voltage, that is, a voltage difference between the first summed voltage and the second summed voltage, the reference voltage having a third temperature coefficient, that is, the first temperature coefficient and The difference between the second temperature coefficients. The present invention further provides a reference circuit capable of adjusting a temperature coefficient, the main structure comprising: a first current source having an output end grounded; a first reference unit having one end connected to the input end of the first current source a first node, the other end is connected to a supply voltage; a second reference unit having one end connected to the input end of the first current source to a first node; and a second current source having an output end connected to the second reference unit The other end of the second node is connected to the input voltage by the input terminal; wherein the first reference unit has 200923611. There is a first total voltage of the first temperature coefficient, and the second reference unit has a second temperature coefficient. a second summing voltage; the supply voltage and the second node have a reference voltage, that is, a voltage difference between the first summing voltage and the second summing voltage, the reference voltage having a third temperature coefficient, That is, the difference between the first temperature coefficient and the second temperature coefficient. [Embodiment] First, please refer to FIG. 2, which is a circuit configuration diagram of a preferred embodiment of the reference circuit of the present invention. As shown, the main structure of the reference circuit includes a first current source Ια, a second current source Ib, a first reference unit 21, and a second reference unit 23. The input end of the first current source 1 is connected to the supply voltage VDD; one end of the first reference unit 21 is connected to the output end of the first current source 1 8 at the first node ISh, and the other end is grounded; The output of one current source IA is at the first node Ν!, the other end is connected to the input end of the second current source IB to the second node N2; and the output end of the second current source IB is grounded. I, the current difference (IA-IB) between the first current source IA and the second current source IB may be biased to the first reference unit 21 such that the first reference unit 21 has a first temperature coefficient; Add the total voltage Vpu). The second current source IB may be biased to the second reference unit 23 such that the second reference unit 23 has a second summed voltage V(yi) of a second temperature coefficient /3 (γι). The voltage difference (V(XJ)_V(YI)) between the total voltage and the second total voltage YI) is the reference voltage VreF ' on the second node N2, that is, VrefS^P^-V^y!) . The reference voltage Vref has a third temperature coefficient 200923611 VREF, and the third temperature coefficient y3REF is a difference between the first temperature coefficient y3 (XJ) and the second temperature coefficient (YI), ie, 5 REF=Lu (XJ) · (YI). In the present invention, one of the first current source IA and the second current source IB is an adjustable current source, so that the current between the two current sources IA or the second current source IB can be changed by the adjustment of the first current source IA or the second current source IB. Difference (IA-IB), such that the voltage difference (V()U) - V(YI) between the first reference unit 21 and the second reference unit 23 and the temperature coefficient difference (/3 (xj) - y3 (γι)) Change with the person. Thus, the correction can be adjusted based on the reference voltage VREF obtained by the voltage difference (V(yi)) and the temperature coefficient difference (yS (xj) - /S (γι)) and its third temperature coefficient /3REF. The first reference unit 21 includes a plurality of semiconductor elements 211, 212, and 213 connected in series. Each of the semiconductor elements 211, 212, and 213 is a semiconductor element connected in a diode form, and can be selected as a P-channel galvanic half. a transistor, an N-channel MOS transistor, a P-type bipolar transistor, an N-type bipolar transistor, a P-type junction field effect transistor, an N-type junction field effect transistor, One of a PN diode, a Zener diode, and a Schottky diode. The semiconductor elements 211, 212, and 213 of the first reference unit 21 of this embodiment may also be selected by mashup, using different types of semiconductor elements, for example, the semiconductor element 211 is a P-channel MOS transistor, a semiconductor. Element 212 is a PN diode and semiconductor element 213 is an N-channel MOS transistor. Each of the semiconductor elements 211, 212, 213 has a junction voltage VgS (XI), Vd (xn-I), V 〇 S (XN) and its corresponding temperature coefficient /5 (XI), 10,000 (XN- 1), 10,000 (XN). The current difference (Ia-Ib) between the current source Ια and the 电流2 current source Ib may be biased toward the 200923611 reference unit 21' such that the first reference unit 21 has the first-th total voltage V of the first temperature j-number () XJ) 'The first total voltage ν(10) is the sum of the junction voltages of the conductor elements 2^2 13, for example: 〇〇), Vgs(x1)+."+Vd(xn i)+Vgs (10)) And the first temperature coefficient 10,000 (10): is the sum of the temperature coefficients of the semiconductor elements 2U, 212, 2U, for example: ° ° wide 6 (χι) + · · · + / 3 (χν.ι) + / 3 ( Χν). Ο
士第一參考單元21除了採用調整第一電流源^與第二電 机源ιΒ間的電流差(Ia_Ib)的料，以改變第一加總電壓v(xj) 及其第一溫度係數另可選擇由第一參考單元21内的 半導體7G件的設置數量或者改變各半導體元件的長寬比而 進-步調整，並且第-溫度係數〜)亦可調整為負溫度係 數或正溫度係數。 又，第二參考單元23包括有至少一半導體元件231， 半導體元件231係為連接成二極體形式的半導體元件，並 且係可選擇為一 Ρ通道金氧半電晶體、一 Ν通道金氧半^ 晶體、一 Ρ型雙載子電晶體、一 Ν型雙載子電晶體、—ρ 型接面場效電晶體、一 Ν型接面場效電晶體、一 ρΝ二極體、 一齊納二極體及一蕭特基二極體之其中之—者，並且半導 體元件231具有一接面電壓及其相對應的溫度係數 /5 (γι)。 第二電流源IB可偏壓於第二參考單元23，以使得第一 參考單元23具有一第二溫度係數pap的第二加總電壓 Vo^ ’第二加總電壓V(YI}係為半導體元件231接面電壓， 例如：Vo^Vgso^’而第二溫度係數石(γΙ>係為半導體元件 200923611 231之溫度係數万⑺），例如 當然，第二束去抑-β m、— β⑽。 之電流值的方1 早723除了使用調整第二電流源工 :=1變第二加總電壓V-及其第二溫度係 ΐ參照如第—參考單Μ，藉由改變半導 ‘v(二第篁或t導體元件的長寬比而調整第二加總 f 度係數“F將可進一步調整。此外，第二溫卢The first reference unit 21 uses a material that adjusts the current difference (Ia_Ib) between the first current source and the second motor source ι to change the first total voltage v(xj) and its first temperature coefficient. The number of semiconductor 7G members in the first reference unit 21 is selected or the aspect ratio of each semiconductor element is changed to be further adjusted, and the first temperature coefficient 〜 can also be adjusted to a negative temperature coefficient or a positive temperature coefficient. Moreover, the second reference unit 23 includes at least one semiconductor element 231, and the semiconductor element 231 is a semiconductor element connected in the form of a diode, and may be selected as a channel of MOS, a channel of MOS, and a channel of MOS. ^ Crystal, a double-type bipolar transistor, a double-type bipolar transistor, a p-type junction field effect transistor, a tantalum junction field effect transistor, a ρΝ diode, a Zener The polar body and a Schottky diode are among them, and the semiconductor element 231 has a junction voltage and its corresponding temperature coefficient /5 (γι). The second current source IB can be biased to the second reference unit 23 such that the first reference unit 23 has a second summed voltage Vo of a second temperature coefficient pap. The second summed voltage V(YI} is a semiconductor. The element 231 is connected to a surface voltage, for example, Vo^Vgso^' and the second temperature coefficient stone (γΙ> is a temperature coefficient 10,000 (7) of the semiconductor element 200923611 231), for example, of course, the second beam is de-suppressed-β m, —β(10) The current value of the square 1 early 723 in addition to the use of the adjustment of the second current source: = 1 to the second total voltage V - and its second temperature system 如 refer to the first - reference unit, by changing the semi-conducting 'v (The second 篁 or t conductor element aspect ratio and the adjustment of the second sum total f degree coefficient "F will be further adjustable. In addition, the second Wenlu
^數亦可調整為正溫度係數或負溫度係數之其中之二 者。 又，如上所述，第=、'田痒及如η 〇办袖 罘—，皿度係數点R E F係為第一溫度係數 万(XJ)與第二溫度係數P 的莫估 双P(YI)的差值（石par沒(YI))，則第一溫度 係數石⑽或第-溫度係數〜進行調整時，第三溫度係數 “F將跟隨著變化。藉此，本發日轉考電路亦可將第一溫 度係數y5⑻)與第二溫度係數〜)調整為相同的溫度係數， 以使得兩者間的差〇广々⑽)為零。則第三溫度係數 成為-零溫度係數’轉考電壓V·可成為受溫度影 響的參考電壓，以增加應用時的穩定性。 虽然’本發明參考電路之另—實施例中，亦可根據後 續應用電路(例如：溫度感測H)對於溫度係數的應用需求而 將第一溫度係數冷與第二溫度係數冷(γι)間的差值（0⑻) -/5 (ΥΙ>)調整為正溫度係數或負溫度係數，則應用電路可根據 參考電壓VREF之變動而得知溫度的變化。 e月參閱第3圖係為本發明參考電路又一實施例之電路 結構圖。如圖所示，本實施例參考電路之主要結構與第2 200923611 圖所不之參考電路大致相同，包括有H流源I、一 第-電机源ΙΒ、一第一參考單元21及一第二參考單元η。 然^發明中之第—參考單元21所包括的半導體元件 同類ϋίΐ7" 23所包括的半導體元件可全部選擇使用相 同齡的+導體元件。例如：全部選擇ρ通道金氧半電晶 體、Ν通道金氧半電晶體、ρ型雙載子電晶體、ν型雙載子 電晶體、ρ型接面場效電晶體、Ν型接面場效電晶體、ρΝ 二極體、一齊納二極體或蕭特基二極體。 如此，不僅可便利於電路佈@，並且可避免半導體元 件之7G件特性不同而產生不匹配的情形，於製程時減少製 程偏移的機會而增加電路設計的準確度，藉此以得到一正 確的參考電壓VREF及其第三溫度係數万咖。 本實施例係以p通道金氧半電晶體為例進行說明。參 考電路之第-參考單元21之半導體元件214、215、216及 一第二參考單元23之半導體元件232、233皆為P通道金 氧半電晶體。 …中參考單元23係選擇包括有複數個半導體元 件232、233 ’如此將可擴大參考電壓'ρ的電壓範圍，以 提供多組的參考電壓VREF 〇 請參閱第4圖係為本發明參考電路又一實施例之電路 結構圖。如圖所示，本發明第—電流源以係包括有一第三 半導體元件25，而第二電流源Ib#包括有—第四半導體元 件27。第三半導體元件25係可選擇為一 p通道金氧半電晶 體、一 P型雙載子電晶體及—p型接面場效電晶體之其中 200923611 . 之一者。而該第四半導體元件27係可選擇為一 N通道金氧 半電晶體、一 N型雙載子電晶體及一 N型接面場效電晶體 之其中之一者。 在本發明中，第一電流源IA及第二電流源IB亦可經由 調整第三半導體元件25及第四半導體元件27之長寬比而 分別改變電流值大小，藉此將可調整出一適當的電流差 (IA-IB)，而得到一實際需求的參考電壓VREF及其第三溫度 係數卢REF。 ^ 又，本發明參考電路尚包括有一第一偏壓單元31及一 第二偏壓單元33，其中第一偏壓單元31連接供應電壓 VDD，用以產生偏壓電壓對於第三半導體元件25進行偏壓， 以產生該第一電流源IA ;而第二偏壓單元33連接於第一偏 壓單元31及接地間，用以產生偏壓電壓對於第四半導體元 件27進行偏壓，以產生該第二電流源IB。 當然，本發明另一實施例中，該第一電流源IA係可包 括有多個串聯之第三半導體元件25所產生，而該第二電流 I 源IB係可包含有一或多個串聯之第四半導體元件27所產 生。並且，可根據第三半導體元件25之數量而增設多個依 序疊接於該供應電壓VDD之第一偏壓單元31，並分別產生 偏壓電壓至對應之第三半導體元件25，及可根據第四半導 體元件27之數量而增設多個疊接於第一偏壓單元31與接 地間之第二偏壓單元33，並分別產生偏壓電壓至對應之第 四半導體元件27。藉此提高第一偏壓單元31及第二偏壓單 元33之偏壓能力，以提供足夠的第一電流源IA及第二電流 12 200923611 源Ib 0 又，本發明參考電路尚包括有-可變電阻器35，並且 可變電阻ϋ 35連接於第—偏壓單元31與第二偏壓單元％The ^ number can also be adjusted to two of the positive temperature coefficient or the negative temperature coefficient. Further, as described above, the first =, 'Tian itching and η 〇 罘 罘 , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , The difference (stone par not (YI)), when the first temperature coefficient stone (10) or the first temperature coefficient ~ is adjusted, the third temperature coefficient "F will follow the change. Thereby, the daily conversion circuit The first temperature coefficient y5(8)) and the second temperature coefficient 〜) may also be adjusted to the same temperature coefficient such that the difference between the two is greater than (10)). Then the third temperature coefficient becomes -zero temperature coefficient 'turn The test voltage V· can be a temperature-dependent reference voltage to increase the stability of the application. Although the invention of the reference circuit of the present invention can also be used according to the subsequent application circuit (for example: temperature sensing H) The application of the coefficient can adjust the difference between the first temperature coefficient cold and the second temperature coefficient cold (γι) (0(8)) -/5 (ΥΙ>) to a positive temperature coefficient or a negative temperature coefficient, and the application circuit can be based on the reference. The change in voltage VREF is used to know the change in temperature. See Figure 3 for e month. A circuit structure diagram of still another embodiment of the circuit. As shown in the figure, the main structure of the reference circuit of the present embodiment is substantially the same as that of the reference circuit of the second embodiment of the present invention, including the H current source I and a first motor source. A first reference unit 21 and a second reference unit η. However, the semiconductor element included in the first reference unit 21 of the invention may be selected from the same age of + conductor elements. For example: all select ρ channel MOS semi-transistor, Ν channel MOS semi-transistor, ρ-type bipolar transistor, ν-type bipolar transistor, ρ-type junction field effect transistor, Ν-type junction field The effect transistor, the ρΝ diode, the Zener diode or the Schottky diode. This can not only facilitate the circuit board @, but also avoid the mismatch of the 7G characteristics of the semiconductor component. The process reduces the chance of process offset and increases the accuracy of the circuit design, thereby obtaining a correct reference voltage VREF and its third temperature coefficient. This embodiment uses a p-channel MOS transistor as an example. Carry out The semiconductor elements 214, 215, 216 of the first reference unit 21 of the reference circuit and the semiconductor elements 232, 233 of a second reference unit 23 are all P-channel MOS transistors. The reference unit 23 of the reference circuit is selected to include a plurality of The semiconductor elements 232, 233' will thus expand the voltage range of the reference voltage 'ρ to provide a plurality of sets of reference voltages VREF. Please refer to FIG. 4 for a circuit configuration diagram of still another embodiment of the reference circuit of the present invention. As shown, the first current source of the present invention includes a third semiconductor component 25, and the second current source Ib# includes a fourth semiconductor component 27. The third semiconductor component 25 can be selected as a p-channel MOS. One of the transistors, a P-type bipolar transistor, and a p-type junction field effect transistor, 200923611. The fourth semiconductor component 27 can be selected as one of an N-channel MOS transistor, an N-type bipolar transistor, and an N-type junction field effect transistor. In the present invention, the first current source IA and the second current source IB can also change the magnitude of the current value by adjusting the aspect ratios of the third semiconductor component 25 and the fourth semiconductor component 27, thereby making it possible to adjust an appropriate value. The current difference (IA-IB) is obtained by a practically required reference voltage VREF and its third temperature coefficient Lu REF. Further, the reference circuit of the present invention further includes a first biasing unit 31 and a second biasing unit 33, wherein the first biasing unit 31 is connected to the supply voltage VDD for generating a bias voltage for the third semiconductor component 25. Biasing to generate the first current source IA; and the second biasing unit 33 is connected between the first biasing unit 31 and the ground for generating a bias voltage to bias the fourth semiconductor component 27 to generate the The second current source IB. Of course, in another embodiment of the present invention, the first current source IA may include a plurality of third semiconductor elements 25 connected in series, and the second current I source IB may include one or more series connected Four semiconductor elements 27 are produced. In addition, a plurality of first biasing units 31 sequentially connected to the supply voltage VDD may be added according to the number of the third semiconductor elements 25, and a bias voltage is respectively generated to the corresponding third semiconductor component 25, and may be A plurality of second biasing units 33, which are overlapped between the first biasing unit 31 and the ground, are added to the fourth semiconductor component 27, and a bias voltage is generated to the corresponding fourth semiconductor component 27, respectively. Thereby, the biasing capability of the first biasing unit 31 and the second biasing unit 33 is increased to provide sufficient first current source IA and second current 12 200923611 source Ib 0. Further, the reference circuit of the present invention includes - The variable resistor 35 is connected, and the variable resistor ϋ 35 is connected to the first bias unit 31 and the second bias unit
間。由於電路製料往往會發生製程偏移的情形，而使得 參考電路所產生的參考龍％及其第三溫錢 與最初電路設計的值不同。 REF 藉由可變電阻器35的設置，可變電阻器35之 化將調控該第二偏壓電壓之偏壓值，以改變第四半 件27所產生的第二電流源Ιβ，則該參考電壓％及其 溫度係數/3 REF即可進行修正調整。 因此’本發明之參考電路透過可變電阻器％的微猶 用’而修正製程偏移时所造成的誤差，藉此以得到一正 相參考電壓VREF及其第三溫度係數点挪。between. Since the circuit material tends to have a process offset, the reference peak generated by the reference circuit and its third temperature are different from the values of the original circuit design. REF is set by the variable resistor 35, and the variable resistor 35 regulates the bias value of the second bias voltage to change the second current source Ιβ generated by the fourth half 27, then the reference The voltage % and its temperature coefficient /3 REF can be corrected. Therefore, the reference circuit of the present invention corrects the error caused by the process offset by the micro-use of the variable resistor %, thereby obtaining a positive phase reference voltage VREF and its third temperature coefficient point shift.
π參閱第5 «1係為本發明參考電路又—實施例之電路 、〜構圖。如®所示’參考電路之主要結構包括有—第一電 〜源U、一第二電流源Ιβ、一第一參考單元51、一第二參 考單元53。第-電流源以之輸出端接地；第—參考單元w =-端連接第-電流源Ια之輸人端於第—節點^，另一端 ，供應電歷Vdd :第二參考單元3之一端連接第一電流 ^ A之輪人端於第-_Nl，另1連接第二電流源^之 於第二節點％;而第二電流源L之輸人端連接供應 其中，第一電流源I 可偏壓於第一參考單元 A與第二電流源Ib間的電流差(Ia-Ib) 51，以使得第一參考單元51具有第 13 200923611 一溫度係數冷⑻}之第一加總電壓V(xj)。第二電流源ιΒ可偏 壓於第二參考單元53，以使得第二參考單元23具有一第二 溫度係數/3(叫的第二加總電壓V(YI)。 第一加總電壓V()a)與第二加總電壓V(YI)間的電壓差 即為該供應電壓vDD與第二節點ν2間之參考電 壓Vref ’即丨〉。該參考電壓VREF具有一第三 溫度係數泠REF，該第三溫度係數石REF為第一溫度係數万⑽ p 與第二溫度係數0(YI)間之差值，即々REF=/3(xdYi)。π refers to the fifth «1 is the reference circuit of the present invention - the circuit of the embodiment, ~ composition. The main structure of the reference circuit as shown in Fig.® includes a first electric source ~ a source U, a second current source Ι β, a first reference unit 51, and a second reference unit 53. The first current source is grounded at the output end; the first reference unit w=-end is connected to the input end of the first current source Ια at the first node, and the other end is supplied with the electrical calendar Vdd: one end of the second reference unit 3 is connected The first current ^A wheel is connected to the first -_Nl, the other is connected to the second current source to the second node %; and the second current source L is connected to the input terminal, and the first current source I is biased Pressing a current difference (Ia-Ib) 51 between the first reference unit A and the second current source Ib such that the first reference unit 51 has a first total voltage V (xj) of the 13th 200923611 temperature coefficient cold (8)} ). The second current source ι is biased to the second reference unit 53 such that the second reference unit 23 has a second temperature coefficient /3 (called the second total voltage V (YI). The first total voltage V ( a) The voltage difference between the second sum voltage V(YI) is the reference voltage Vref ' between the supply voltage vDD and the second node ν2. The reference voltage VREF has a third temperature coefficient 泠REF, and the third temperature coefficient REF is the difference between the first temperature coefficient 10,000 (10) p and the second temperature coefficient 0 (YI), that is, 々REF=/3 ( xdYi).
Li 本發明中第一電流源IA與第二電流源IB之其中之一者 係為可調式的電流源，因此可透過第一電流源IA或第二電 流源IB的調整而改變兩者間的電流差(Ia_Ib)，並依此修正該 參考電壓Vref及其第三溫度係數/SREF，如此將可求得一溫 度係數穩定的參考電壓VREF。 第一參考單元51包括有複數個串聯連接之半導體元件 511、 512、513 ’各半導體元件5U、512、513係為連接成 一極體形式的半導體元件，可分別選擇為一 P通道金氧半 電晶體、-N通道金氧半電晶體、一 p塑雙載子電晶體、 - N型雙載子電晶體、—p型接面場效電晶體、一㈣接 面場效電晶體、一 PN二極體、—齊納二極體及—蕭特基二 極體之其中之一者。 此外’本實施例之第一參考單元51之半導體元件5U、 512、 513亦可選擇混搭的方式，使用不同類型的半導體元 件所組合而成，例如··半導體元件511係為N型雙載子電 晶體、半導體元件512係為pN二極體，而半導體元件513 14 200923611 係為P型雙載子電晶體。每一半導體元件511、512、513 皆具有一接面電壓VBe(X1)、V〇(X2)、VbECXW及其相對應的溫 度係數石(XI)、/3 (X2)、点(XN)。 此外，第一電流源IA與第二電流源IB間的電流差(IA-IB) 可偏壓於第一參考單元51，以使得第一參考单元51具有第 一溫度係數/3⑻)之第一加總電壓乂⑻）’第一加總電壓V(xj) 係為半導體元件511、512、513之接面電壓的總合，例如： '^〇0厂^^8£(父1)+'\/〇(乂2)+...+'^6£(乂'^)’而第一溫度係數 5(XJ)係為 半導體元件511、512、513之溫度係數的總合，例如：yS(XJ)= 召(Xl)+厶(X2)+...+ /5(XN)。 第一參考單元51除了採用調整第一電流源IA與第二電 流源IB間的電流差(IA-IB)的方式，以改變第一加總電壓V(XJ) 及其第一溫度係數另可選擇由第一參考單元51内的 半導體元件的設置數量或者改變各半導體元件的長寬比而 進一步調整’並且第一溫度係數βρα)亦可調整為負溫度係 數或正溫度係數。 又，第二參考單元53包括有至少一半導體元件531， 半導體元件531係為連接成二極體形式的半導體元件，並 且係可選擇為一 Ρ通道金氧半電晶體、一 Ν通道金氧半電 晶體、一 Ρ型雙載子電晶體、一 Ν型雙載子電晶體、一 Ρ 型接面場效電晶體、一 Ν型接面場效電晶體、一 ΡΝ二極體、 一齊納二極體、及一蕭特基二極體之其中之一者，並且半 導體元件531具有一接面電壓VBE(Y1)及其相對應的溫度係 數沒(γι)。 15 200923611 此外，第二電流源ιΒ可偏壓於第二參考單元μ，以使 得第二參考單以具有—第二溫度係數‘的第二城電 壓v(YI)，第二加總電壓ν(Υι)係為半導體元件531接面電壓， 例如：Vo^Vbryd，而第二溫度係數係為半導體元件m 之溫度係數万(YI}，例如：々(γι)=万(γι)。 當然，第二參考單元53除了使用調整第二電流源I之 電流值的方式來改變第二加總電壓ν(γι)及其第二溫二In the present invention, one of the first current source IA and the second current source IB is an adjustable current source, so that the adjustment between the first current source IA or the second current source IB can be changed between the two. The current difference (Ia_Ib), and the reference voltage Vref and its third temperature coefficient /SREF are corrected accordingly, so that a reference voltage VREF with a stable temperature coefficient can be obtained. The first reference unit 51 includes a plurality of semiconductor elements 511, 512, 513 connected in series. Each of the semiconductor elements 5U, 512, and 513 is a semiconductor element connected in a pole form, and can be selected as a P-channel MOS. Crystal, -N channel MOS transistor, a p-type bi-carrier transistor, - N-type bipolar transistor, -p-type junction field effect transistor, one (four) junction field effect transistor, a PN One of the diode, the Zener diode, and the Schottky diode. In addition, the semiconductor elements 5U, 512, and 513 of the first reference unit 51 of the present embodiment may be selected by a mashup method using a combination of different types of semiconductor elements, for example, the semiconductor element 511 is an N-type double carrier. The transistor and the semiconductor element 512 are pN diodes, and the semiconductor elements 513 14 200923611 are P-type bipolar transistors. Each of the semiconductor elements 511, 512, and 513 has a junction voltage VBe (X1), V 〇 (X2), VbECXW, and their corresponding temperature coefficient stones (XI), /3 (X2), and dots (XN). Furthermore, the current difference (IA-IB) between the first current source IA and the second current source IB may be biased to the first reference unit 51 such that the first reference unit 51 has a first temperature coefficient /3 (8)) first The total voltage 乂(8)) 'the first total voltage V(xj) is the sum of the junction voltages of the semiconductor elements 511, 512, and 513, for example: '^〇0厂^^8£(parent 1)+' \/〇(乂2)+...+'^6£(乂'^)' and the first temperature coefficient 5 (XJ) is the sum of the temperature coefficients of the semiconductor elements 511, 512, 513, for example: yS (XJ)= Call (Xl)+厶(X2)+...+ /5(XN). The first reference unit 51 adopts a method of adjusting a current difference (IA-IB) between the first current source IA and the second current source IB to change the first total voltage V(XJ) and the first temperature coefficient thereof. The selection of the number of semiconductor elements in the first reference unit 51 or the change of the aspect ratio of each semiconductor element is further adjusted 'and the first temperature coefficient βρα) may also be adjusted to a negative temperature coefficient or a positive temperature coefficient. Moreover, the second reference unit 53 includes at least one semiconductor element 531, and the semiconductor element 531 is a semiconductor element connected in the form of a diode, and may be selected as a channel MOS transistor, a channel MOS half. A transistor, a 双 type bipolar transistor, a 双 type double carrier transistor, a 接 type junction field effect transistor, a 接 type junction field effect transistor, a ΡΝ diode, a Zener One of the polar body and one Schottky diode, and the semiconductor element 531 has a junction voltage VBE (Y1) and its corresponding temperature coefficient (γι). 15 200923611 Further, the second current source ιΒ may be biased to the second reference unit μ such that the second reference unit has a second city voltage v(YI) having a second temperature coefficient, and a second total voltage ν ( Υι) is a junction voltage of the semiconductor element 531, for example, Vo^Vbryd, and the second temperature coefficient is a temperature coefficient 10,000 (YI) of the semiconductor element m, for example: 々 (γι) = 10,000 (γι). The second reference unit 53 changes the second total voltage ν(γι) and the second temperature thereof in addition to adjusting the current value of the second current source I.
月⑽’亦可選擇參照如第-參考單元5卜藉由改變半導體 元件的設置數量或半導體元件的長寬比而調整第二加總電 壓V(yi〉及其第二溫度係數点(ΥΙ〉’如此對於參考電壓及 其第二溫度係數^REF將可進一步調整。此外，第二溫产係 數冷亦可調整為正溫度係數或負溫度係數之其中之一 者。 又，如上所述’第三溫度係數—為第—溫度係數 厶(χ·0與第二溫度係數；S (YI>的差值（冷(XJr冷(ΥΙ))，則第一溫度 係數/3 (x_〇或第一溫度係數/5 (ΥΙ}進行調整時，則第三溫度係 數0REF將跟隨著變化。藉此，本發明參考電路亦可將第一 溫度係數yS (χυ與第二溫度係數万(叫調整為相同的溫度係 數，以使得兩者間的差（冷(χυ-泠為零。則第三溫度係數 冷REF成為一零溫度係數，而參考電壓Vref可成為一不受溫 度影響的參考電壓，以增加應用時的穩定性。 當然，本發明參考電路之另一實施例中，亦可根據後 續應用電路(例如：溫度感測器）對於溫度係數的應用需求而 將第一溫度係數冷(χ_〇與第二溫度係數冷(ΥΙ)間的差值（石 200923611 . -/3 σ I))調整為正溫度係數或負溫度係數，則可藉由參考電壓 VREF之變動而得知溫度的變化。 請參閱第6圖係為本發明參考電路又一實施例之電路 結構圖。如圖所示，本發明第一電流源ιΑ係包括有一第三 半導體元件55，而第二電流源IB係包括有一第四半導體元 件57。第三半導體元件55係可選擇為一 P通道金氧半電晶 體、一 P型雙載子電晶體及一 P型接面場效電晶體之其中 之一者，而該第四半導體元件57係可選擇為一 N通道金氧 D 半電晶體、一 N型雙載子電晶體及一 N型接面場效電晶體 之其中之一者。The month (10)' may also select, as the first reference unit 5, adjust the second total voltage V (yi> and its second temperature coefficient point by changing the number of semiconductor elements or the aspect ratio of the semiconductor element (ΥΙ) 'Therefore, the reference voltage and its second temperature coefficient ^REF will be further adjusted. In addition, the second temperature coefficient can be adjusted to one of the positive temperature coefficient or the negative temperature coefficient. The three temperature coefficient is the first temperature coefficient 厶 (χ·0 and the second temperature coefficient; S (YI> difference (cold (XJr cold (ΥΙ)), then the first temperature coefficient /3 (x_〇 or When a temperature coefficient /5 (ΥΙ} is adjusted, the third temperature coefficient 0REF will follow the change. Thereby, the reference circuit of the present invention can also adjust the first temperature coefficient yS (χυ and the second temperature coefficient 10,000 (called adjustment) The same temperature coefficient, so that the difference between the two (cold (χυ-泠 is zero. Then the third temperature coefficient cold REF becomes a zero temperature coefficient, and the reference voltage Vref can become a temperature-independent reference voltage, To increase the stability of the application. Of course, the present invention refers to electricity In another embodiment, the first temperature coefficient may be cold (the difference between the χ_〇 and the second temperature coefficient cold (ΥΙ) according to the application requirement of the subsequent application circuit (eg, temperature sensor) for the temperature coefficient. The value (stone 200923611 . -/3 σ I)) is adjusted to a positive temperature coefficient or a negative temperature coefficient, and the change in temperature can be known by the variation of the reference voltage VREF. Please refer to Fig. 6 for the reference circuit of the present invention. A circuit configuration diagram of an embodiment. As shown, the first current source ι of the present invention includes a third semiconductor component 55, and the second current source IB includes a fourth semiconductor component 57. The third semiconductor component 55 is Alternatively, one of a P-channel MOS transistor, a P-type dual-carrier transistor, and a P-type junction field effect transistor can be selected, and the fourth semiconductor component 57 can be selected as an N channel. One of the gold oxide D semi-transistor, an N-type bipolar transistor, and an N-type junction field effect transistor.
在本發明中，第一電流源IA及第二電流源IB亦可經由 調整第三半導體元件55及第四半導體元件57之長寬比而 分別改變電流值大小，藉此調整出一適當的電流差(IA-IB)， 以得到一實際需求的參考電壓VREF及其第三溫度係數yS REF ° 又，本發明參考電路尚包括一第一偏壓單元71及一第 I 二偏壓單元73。其中第一偏壓單元71接地，用以產生偏壓 電壓對於第三半導體元件55進行偏壓，以產生該第一電流 源IA ;而第二偏壓單元73連接於供應電壓VDD與第一偏壓 單元71間，用以產生偏壓電壓對於第四半導體元件57進 行偏壓*以產生該苐二電流源Ib。 當然，本發明另一實施例中，該第一電流源ΙΑ係可包 括有多個串聯之第三半導體元件55所產生，而該第二電流 源ΙΒ係可包含有一或多個串聯之第四半導體元件57所產 17 200923611 電第壓早 並分別產生偏壓 件55 ^^半導體元件57，及可根據第三半導體元 I二:/曾設多個依序疊接於第二偏壓單元73與接 = 元71 ’並分別產生偏壓電壓至對應之第 ①55。藉此提高第-偏壓單元71及第二偏壓單 =3之偏壓能力，以提供㈣的第—電流源U及第二電流 源丄Β。 Ο 本發月參考電路尚包括有一可變電阻器乃 ^變電阻ϋ75連接於第1壓單元71熱 變電阻器75的設置，可變雷 糟由Τ 第-__ 值，=:== 出溫度係❹ 因此，本發明之參考電路透過可變電阻器75的微調作 用二修正製程偏移因素所造成的誤差，藉此得到一正確 的參考電壓VREF及其第三溫度魏&F。 正確 以上所述者’僅為本發明之較佳實施例而已，並 來限定本發明實施之_，即凡依本發明申 述之形狀 '構造、賴補相為之均㈣㈣修 應包括於本發明之申請專利範圍内。 【圖式簡單說明】 構圖 第1圖：係為習用參考電路之電路鈐 18 200923611 . 第2圖：係為本發明參考電路一較佳實施例之電路結構圖。 第3圖：係為本發明參考電路又一實施例之電路結構圖。 第4圖：係為本發明參考電路又一實施例之電路結構圖。 苐5圖·係為本發明參考電路又一實施例之電路結構圖。 第6圖：係為本發明參考電路又一實施例之電路結構圖。 【主要元件符號說明】 11 電流鏡電路 13 可變電阻器 15 雙載子電晶體 21 第一參考單元 211 半導體元件 212 半導體元件 213 半導體元件 214 半導體元件 215 半導體元件 216 半導體元件 23 第二參考單元 231 半導體元件 232 半導體元件 233 半導體元件 25 第三半導體元件 27 第四半導體元件 31 第一偏壓單元 33 第二偏壓單元 35 可變電阻器 51 第一參考單元 511 半導體元件 512 半導體元件 513 半導體元件 53 第二參考單元 531 半導體元件 55 第三半導體元件 57 第四半導體元件 71 第一偏壓單元 73 第二偏壓單元 75 可變電阻器 N1 第一節點 N2 第二節點 19In the present invention, the first current source IA and the second current source IB can also change the magnitude of the current value by adjusting the aspect ratio of the third semiconductor element 55 and the fourth semiconductor element 57, thereby adjusting an appropriate current. The difference (IA-IB) is used to obtain a practically required reference voltage VREF and its third temperature coefficient yS REF °. Further, the reference circuit of the present invention further includes a first biasing unit 71 and a first two biasing unit 73. The first biasing unit 71 is grounded to generate a bias voltage to bias the third semiconductor component 55 to generate the first current source IA; and the second biasing unit 73 is coupled to the supply voltage VDD and the first bias The voltage unit 71 is configured to generate a bias voltage to bias the fourth semiconductor element 57* to generate the second current source Ib. Of course, in another embodiment of the present invention, the first current source system may include a plurality of third semiconductor elements 55 connected in series, and the second current source system may include one or more series connected fourth The semiconductor element 57 produces 17 200923611 electric first voltage and generates a biasing member 55 ^ ^ semiconductor element 57, respectively, and may be sequentially stacked on the second biasing unit 73 according to the third semiconductor element I: And the connection = element 71' and generate a bias voltage to the corresponding 155th. Thereby, the biasing ability of the first biasing unit 71 and the second biasing single = 3 is increased to provide the (four) first current source U and the second current source 丄Β. Ο The reference circuit of the present month further includes a variable resistor connected to the setting of the thermal resistor 75 of the first pressing unit 71, and the variable thunder is determined by the first -__ value, =:== the temperature Therefore, the reference circuit of the present invention corrects the error caused by the process offset factor by the fine adjustment function of the variable resistor 75, thereby obtaining a correct reference voltage VREF and its third temperature Wei & F. It is to be understood that the above description is only a preferred embodiment of the present invention, and is intended to limit the implementation of the present invention, that is, the shape of the structure according to the present invention, and the compensation of the four phases (four) (four) are included in the present invention. Within the scope of the patent application. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a conventional reference circuit. 2009 18 200923611 . Fig. 2 is a circuit diagram of a preferred embodiment of the reference circuit of the present invention. Figure 3 is a circuit diagram showing still another embodiment of the reference circuit of the present invention. Figure 4 is a circuit diagram showing still another embodiment of the reference circuit of the present invention. Figure 5 is a circuit diagram of still another embodiment of the reference circuit of the present invention. Figure 6 is a circuit diagram showing still another embodiment of the reference circuit of the present invention. [Main component symbol description] 11 Current mirror circuit 13 Variable resistor 15 Bipolar transistor 21 First reference unit 211 Semiconductor element 212 Semiconductor element 213 Semiconductor element 214 Semiconductor element 215 Semiconductor element 216 Semiconductor element 23 Second reference unit 231 Semiconductor element 232 semiconductor element 233 semiconductor element 25 third semiconductor element 27 fourth semiconductor element 31 first biasing unit 33 second biasing unit 35 variable resistor 51 first reference unit 511 semiconductor element 512 semiconductor element 513 semiconductor element 53 Second reference unit 531 Semiconductor element 55 Third semiconductor element 57 Fourth semiconductor element 71 First bias unit 73 Second bias unit 75 Variable resistor N1 First node N2 Second node 19