CN1340750A - Low temperature coefficient reference current source generating circuit - Google Patents

Abstract

The invention relates to a low-temperature coefficient reference current source generating circuit, which utilizes a positive temperature coefficient reference current generated by a positive temperature coefficient sensing circuit path of a band gap reference voltage source and utilizes a low-temperature coefficient band gap reference voltage to drive an internal resistor of an integrated circuit with a positive temperature coefficient so as to generate a negative temperature coefficient reference current, and the negative temperature coefficient reference current and the internal resistor are adjusted and combined to obtain a low-temperature coefficient reference current source.

Description

Low temperature coefficient reference current source generating circuit

The invention relates to a reference current source generation circuit, especially a low temperature coefficient reference current source generation circuit which is less affected by temperature fluctuations.

In the design of existing analog circuits, almost all analog circuits of integrated circuits (IC) need to use a reference voltage source and a reference current source for bias (bias), wherein the reference voltage source can use the bandgap ) technology to design low temperature coefficient characteristics, but if you want to generate a reference current source with low temperature coefficient characteristics, you must borrow (bandgap) the reference voltage to drive the low temperature coefficient resistor outside the IC to generate it. Therefore, not only the IC needs additional Pins are used to connect external resistors, which is not conducive to the miniaturization of the circuit.

And if you want to set a resistor inside the IC, because the resistors made by the complementary metal oxide semiconductor (CMOS) IC process have a large positive temperature coefficient, the generated current will vary by tens of percent with the temperature. However, it cannot meet the requirements of low temperature coefficient. Therefore, how to realize the reference current source with low temperature coefficient by using standard CMOS IC process and without connecting external resistors has become an extremely important issue.

Because of this, the creators, in the spirit of active innovation, eagerly thought of a "low temperature coefficient reference current source generation circuit" that can solve the above problems, and finally completed this novel and progressive creation after several researches and experiments.

The purpose of the present invention is to provide a low temperature coefficient reference current source generation circuit, which is less affected by temperature changes.

To achieve the aforementioned purpose, the low temperature coefficient reference current source generating circuit of the present invention has a circuit for generating a bandgap reference voltage source, which provides a low temperature coefficient bandgap reference voltage and a positive temperature coefficient current , the circuit of the present invention has a voltage follower, which generates a voltage following the low temperature coefficient energy band gap reference voltage to drive a resistor with a positive temperature coefficient to generate a current with a negative temperature coefficient, the present invention The circuit of the present invention further has a current mirror circuit for proportionally combining the current with positive temperature coefficient and the current with negative temperature coefficient to obtain a reference current with low temperature coefficient.

Wherein the voltage follower is composed of MOS transistors connected with two gates.

The resistor with positive temperature coefficient is the internal resistor of the integrated circuit.

Wherein the current mirror circuit includes: a first current mirror for proportionally amplifying the current with a positive temperature coefficient; and a second current mirror for proportionally amplifying the current with a negative temperature coefficient.

Wherein the first current mirror is composed of two MOS transistors.

Wherein the second current mirror is composed of two MOS transistors.

Because the present invention has a novel structure, can provide industrial application, and has indeed enhanced effects, it applies for a patent according to law.

In order to enable your examiner to further understand the structure, features and purpose of the present invention, the attached drawings and detailed descriptions of preferred specific embodiments are as follows, wherein:

Fig. 1 is a detailed circuit diagram of the low temperature coefficient reference current source generating circuit of the present invention.

Fig. 2 is a current waveform diagram generated by the low temperature coefficient reference current source generating circuit of the present invention.

Regarding a preferred embodiment of the low temperature coefficient reference current source generating circuit of the present invention, please refer to Fig. 1 first, wherein, the circuit block 11 and 12 are respectively generally known start-up circuit (Startup Circuit) and not powered The bias circuit (Power Supply Independent Bias Circuit) affected by the supply, the startup circuit 11 is used to start the circuit to prevent the circuit from being locked in a zero voltage position, and the bias circuit 12 is based on a bipolar transistor (BJT ) The sensing circuit composed of QP1 and QP2 senses the temperature change, and the sensed result is the voltage ΔV across the resistor R1, which has a positive temperature coefficient change and can generate a fixed current due to the effect of the current mirror I _MP3 ＝ΔV/R1, ΔV＝V _T 1n(N) and I _C ＝I _s (exp(V _BE /V _T )－1), N is the number of transistors, V _T ＝KT/q, K is wave Ziman's constant, q is the electronic charge, T is the absolute temperature, VBE is the potential between the base and the emitter, I _c is the collector current, and I _s is the saturation leakage current. Therefore, I _MP3 is approximately proportional to the absolute temperature.

Since the V _BE of the BJT has a negative temperature coefficient, the sensed ΔV with a positive temperature coefficient and the V _BE3 of the transistor QP3 with a negative temperature coefficient are proportionally amplified and added to obtain a voltage with a low temperature coefficient In this circuit, ΔV amplified by the current mirror formed by MP4 and MP3 and V _BF3 amplified by the ratio of R2/R1 are added together to obtain a low temperature coefficient bandgap reference voltage source V _BGRO .

In order to obtain a current source with a low temperature coefficient, first consider that in the aforementioned circuit for generating the bandgap reference voltage source, since the temperature coefficient of V _T of the BJT is greater than the temperature coefficient of the positive temperature coefficient resistor, the MOS transistor MN5, the resistor The current source I _MP3 produced by the positive temperature coefficient sensing circuit path formed by R1 and BJT transistor QP2 has a positive temperature coefficient, and its characteristic is as shown in the curve (A) of FIG. 2 . Between 75 degrees C, the variation is 0 to +14.1%.

In addition, a voltage follower (voltage fo1 lower) composed of MOS transistors MN6 and MN7 connected to two gates is set in the circuit to generate the low temperature coefficient bandgap reference voltage source V _BGRO through the voltage follower. Follow the voltage to drive the resistor R3 with a positive temperature coefficient inside the IC (it can be a P+, N+, poly or we11 resistor), and a current source I _MP5 with a negative temperature coefficient will be generated due to the positive temperature coefficient of the resistor R3. Its characteristics are shown in the curve (B) of Fig. 2, and the variation is 0 to -20% between -25°C and +75°C.

The aforementioned current source I _MP3 with positive temperature coefficient is amplified by the current mirror formed by MOS transistors MP7 and MP3 to obtain a current source I _R1 with positive temperature coefficient, and the current source I _MP5 with negative temperature coefficient is obtained by The current mirror composed of MOS transistors MP6 and MP5 is amplified to obtain a current source I _R2 with a negative temperature coefficient, wherein the ratio of amplification is determined by the width-to-length ratio (W/L) and the number (M ), in this embodiment, I _R1 =((36/4)/(24/4))×I _MP3 =1.5×I _MP3 , IR2=(24/4)/(24/4)×5 )×I _MP5 ＝0.2×I _MP5 , accordingly, the aforementioned two currents I _MP3 and I _MP5 are combined proportionally to obtain a reference current source with low temperature coefficient Iout=I _R1 ＋I _R2 ＝K×I _MP5 ＋L× I _MP3 , K and L are proportional constants, and the characteristics of Iout are shown in the curve (C) of Figure 2. Between -25°C and +75°C, the change is only 0 to -1.4%, so it can provide an almost Low temperature coefficient reference current source that is not affected by temperature variations.

To sum up, the present invention, regardless of its purpose, means, and efficacy, shows its characteristics that are very different from the conventional technology. It is a major breakthrough in the design of the reference current source, and it is truly an industrial applicability and novelty. and progressive creations, they should meet the requirements for patent application, and the application should be filed in accordance with the law.

Claims (6)

1. a reference current source generating circuit with low temp coefficient is characterized in that, mainly comprises:

One in order to produce the circuit of band-gap reference voltage source, and it provides the band-gap reference voltage of a low-temperature coefficient and the electric current of a positive temperature coefficient (PTC);

One voltage follower device is to produce the voltage of following this low-temperature coefficient band-gap reference voltage, has the resistance of positive temperature coefficient (PTC) to drive one, and produces the electric current of a negative temperature coefficient; And

One current mirroring circuit the electric current of the electric current of this positive temperature coefficient (PTC) and negative temperature coefficient being done the ratio combination, and is obtained the reference current of a low-temperature coefficient.

2. reference current source generating circuit with low temp coefficient according to claim 1 is characterized in that, wherein this voltage follower device is made of the MOS transistor that two gates link to each other.

3. reference current source generating circuit with low temp coefficient according to claim 2 is characterized in that, wherein the resistance of this positive temperature coefficient (PTC) is the resistance for IC interior.

4. reference current source generating circuit with low temp coefficient according to claim 1 is characterized in that, wherein this current mirroring circuit comprises:

First current mirror amplifies the electric current of this positive temperature coefficient (PTC) is done ratio; And

Second current mirror amplifies the electric current of this negative temperature coefficient is done ratio.

5. reference current source generating circuit with low temp coefficient according to claim 4 is characterized in that, wherein this first current mirror is made of two MOS transistor.

6. reference current source generating circuit with low temp coefficient according to claim 4 is characterized in that, wherein this second current mirror is made of two MOS transistor.

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