TWI586101B - Transimpedance amplifier - Google Patents

Description

Transimpedance amplifier

The present invention relates to a Trans-Conductance Amplifier (TIA), and more particularly to a transimpedance amplifier that shortens the transmission delay.

In optical communication systems, the gain and sensitivity of the optical receiver are important characteristics, and both must be optimized to optimize transmission performance. The single-stage transimpedance amplifier used in the conventional optical receiver has a simple structure, but since the overall gain and bandwidth characteristics are closely related to the impedance of the output of the amplifier, the architecture of the single-stage transimpedance amplifier will be The voltage gain is insufficient and there is a problem that high sensitivity cannot be obtained.

Therefore, the architecture of a multi-stage transimpedance amplifier is generally used to design an optical receiver to achieve high voltage gain. The architecture of such a multi-stage transimpedance amplifier usually includes a plurality of single amplifiers connected in series, but since the input current of the optical receiver depends on the infrared rays received by the photodiode, the maximum and minimum values of the input current may exist four. Double the gap. The difference between the maximum and minimum values of the input current will increase the Propagation Delay from the high to low potential of the output of the transimpedance amplifier.

Embodiments of the present invention provide a transimpedance amplifier including a first stage transconductance amplifier, a second stage transconductance amplifier, a third stage amplifier, and a feedback circuit. First level transduction The amplifier has an input end and an output end. The input end of the first stage transduction amplifier is electrically connected to the input current source to receive the first input signal, and the output end of the first stage transduction amplifier outputs the first output signal. . The second stage transconductance amplifier has an input end and an output end, and the input end of the second stage transduction amplifier is electrically connected to the output end of the first stage transconductance amplifier to receive the first output signal, and then the second The output of the stage transconductance amplifier outputs a second output signal. The third stage amplifier has an input end and an output end, and the input end of the third stage amplifier is electrically connected to the output end of the second stage transconductance amplifier to receive the second output signal, and then the output of the third stage amplifier The terminal outputs a third output signal. One end of the feedback circuit is electrically connected to the input end of the first stage transconductance amplifier, and the other end of the feedback circuit is electrically connected to the output end of the third stage amplifier to stabilize the third output signal. The third stage amplifier is composed of a first output stage and a second output stage.

In one embodiment of the invention, the first output stage of the third stage amplifier includes a current source having one end electrically coupled to the supply voltage source to provide a regulated current and the other end coupled to the output of the third stage amplifier.

In one embodiment of the invention, the second output stage of the third stage amplifier comprises a first NMOS transistor and a second PMOS transistor. The first NMOS transistor is coupled to the gate of the second PMOS transistor to form an input of the third stage amplifier. The source of the second PMOS transistor is electrically connected to the supply voltage source, and the drain of the second PMOS transistor is connected to the drain of the first NMOS transistor to the output of the third stage amplifier. The drain of the first NMOS transistor is grounded.

In one of the embodiments of the invention, the transimpedance amplifier includes a reference voltage circuit. The reference voltage circuit includes a constant current unit, a third transistor, a fourth transistor, and a fifth transistor. The constant current unit includes a current mirror and a bias current source. The gate of the third transistor, the gate of the fourth transistor, and the current mirror are connected in parallel with each other. The drain of the fourth transistor forms an output of the reference voltage circuit to output a reference voltage signal. The fifth transistor is connected in parallel to the constant current unit and electrically connected between the supply voltage source and the output terminal of the constant current source.

In summary, the transimpedance amplifier of the embodiment of the present invention is provided with a third-stage amplifier composed of a first output stage and a second output stage, wherein the circuit design of the first output stage belongs to the class A amplifier. The configuration, and the circuit design of the second output stage belongs to the configuration of the class AB amplifier, so that the transimpedance amplifier can have the advantages of the class A amplifier and the class AB amplifier at the same time, thereby shortening the transmission of the transimpedance amplifier. Delayed time. On the other hand, in the reference voltage circuit of the transimpedance amplifier proposed in the embodiment of the present invention, the fifth electro-crystal system is disposed in parallel with the constant current unit, and is electrically connected to the output end of the supply voltage source and the reference voltage circuit. To improve the instability of the reference voltage signal due to temperature changes or changes in the manufacturing process.

The detailed description of the present invention and the accompanying drawings are to be understood by the claims The scope is subject to any restrictions.

1, 2, 3‧‧‧ Transimpedance amplifier

Iin‧‧‧ input current source

TCA1‧‧‧First Stage Transconductance Amplifier

TCA2‧‧‧Second stage transconductance amplifier

TSA3‧‧‧3rd stage amplifier

OUT1‧‧‧ first output stage

OUT2‧‧‧second output stage

TIAp‧‧‧ third output signal

TIAn‧‧‧ reference voltage signal

MN1‧‧‧First NMOS transistor

MN2‧‧‧Second NMOS transistor

MP2‧‧‧second PMOS transistor

MP3‧‧‧ Third PMOS transistor

MP4‧‧‧fourth PMOS transistor

MP5‧‧‧ Fifth PMOS transistor

MN6‧‧‧ sixth NMOS transistor

FB‧‧‧ feedback circuit

RC‧‧‧Resistor Network

B1‧‧‧Bipolar junction transistor

C1, C2‧‧‧ capacitor

R1, R2, R3, R4‧‧‧ resistors

Vcc‧‧‧ supply voltage source

I’‧‧‧ Constant current unit

Is‧‧‧current source

MR‧‧‧current mirror

REF‧‧‧reference voltage circuit

I _Bias ‧‧‧ bias current source

V _M , V _m , Ref1, Ref2‧‧‧ curves

1 is a circuit diagram of a transimpedance amplifier provided by an embodiment of the present invention.

2 is a circuit diagram of a transimpedance amplifier provided by another embodiment of the present invention.

3 is a circuit diagram of a transimpedance amplifier provided by another embodiment of the present invention.

4A is a graph of a reference voltage signal as a function of temperature in a transimpedance amplifier provided by the embodiment of FIG. 2.

4B is a graph of a reference voltage signal as a function of temperature in a transimpedance amplifier provided by the embodiment of FIG. 3.

Various illustrative embodiments are described more fully hereinafter with reference to the accompanying drawings. However, the inventive concept may be embodied in many different forms and should not be construed as being limited to the illustrative embodiments set forth herein. Rather, these exemplary embodiments are provided so that the invention will be exhaustive and It is complete and will fully convey the scope of the inventive concept to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. Similar numbers always indicate similar components.

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, such elements are not limited by the terms. These terms are used to distinguish one element from another. Thus, a first element discussed below could be termed a second element without departing from the teachings of the inventive concept. As used herein, the term "and/or" includes any of the associated listed items and all combinations of one or more.

[Embodiment of Transimpedance Amplifier]

Please refer to FIG. 1. FIG. 1 is a circuit diagram of a transimpedance amplifier according to an embodiment of the present invention. As shown in FIG. 1, the transimpedance amplifier 1 includes a first stage transconductance amplifier TCA1, a second stage transduction amplifier TCA2, a third stage amplifier TSA3, and a feedback circuit FB. The first stage transconductance amplifier TCA1 has an input end and an output end. The input end of the first stage transduction amplifier TCA1 is electrically connected to the input current source Iin to receive the first input signal, and then the first stage transconductance amplifier The output of TCA1 outputs the first output signal. The second stage transconductance amplifier TCA2 has an input end and an output end. The input end of the second stage transduction amplifier TCA2 is electrically connected to the output end of the first stage transduction amplifier TCA1 to receive the first output signal, and then The output of the second stage transduction amplifier TCA2 outputs a second output signal. The third stage amplifier TSA3 has an input end and an output end. The input end of the third stage amplifier TSA3 is electrically connected to the output end of the second stage transconductance amplifier TCA2 to receive the second output signal, and then the third stage. The output of the amplifier TSA3 outputs a third output signal TIAp. One end of the feedback circuit FB is electrically connected to the input end of the first-stage transduction amplifier TCA1, and the other end of the feedback circuit FB is electrically connected to the output end of the third-stage amplifier TSA3 to stabilize the third output signal TIAp. The third stage amplifier TSA3 includes a first output stage OUT1 and a second output stage OUT2.

What is to be taught next is to further explain the working principle of the transimpedance amplifier 1. As shown in FIG. 1, the third stage amplifier TSA3 of the transimpedance amplifier 1 of the present embodiment is first The output stage OUT1 is composed of the second output stage OUT2. The first output stage OUT1 includes a current source Is, wherein one end of the current source Is is electrically connected to the supply voltage source Vcc to provide a stable current, and the other end of the current source Is is connected to the output end of the third stage amplifier TSA3. The second output stage OUT2 includes a first NMOS transistor MN1 and a second PMOS transistor MP2. The first NMOS transistor MN1 is coupled to the gate of the second PMOS transistor MP2 to form an input terminal of the third stage amplifier TSA3. The source of the second PMOS transistor MP2 is electrically connected to the supply voltage source Vcc, and the drain of the second PMOS transistor MP2 is connected to the drain of the first NMOS transistor MN1 to the output terminal of the third-stage amplifier TSA3. The source of the first NMOS transistor MN1 is grounded. That is to say, the first output stage OUT1 belongs to the class A output stage, and the second output stage OUT2 belongs to the class AB output stage. In addition, in this embodiment, the third stage amplifier TSA3 may further include a second NMOS transistor MN2. As shown in FIG. 1, the gate and the source of the second NMOS transistor MN2 are connected to the third stage amplifier TSA3. Output.

In this embodiment, the first output stage OUT1 is a current source Is connected to a reference voltage source (not shown), which is provided for the steady current to be a constant value. When the input current source Iin starts to input the current, the current flowing through the first NMOS transistor MN1 increases, and the current flowing through the second PMOS transistor MP2 decreases, so that the voltage value of the third output signal TIAp increases. Finally, the output voltage of the transimpedance amplifier 1 is controlled by the resistors R1 and R2 in the feedback circuit FB and the base-emitter voltage of the bipolar junction transistor B1.

It should be noted that, in this embodiment, since the third-stage amplifier TSA3 has both the class A output stage and the class AB output stage, the circuit design advantages of the class A output stage and the class AB output stage can be combined. That is to say, the components of the first output stage OUT1 maintain the on state, providing better linearity, and at the same time, the second output stage OUT2 can further improve the efficiency of the third stage amplifier TSA3.

On the other hand, it should be noted in the embodiment that the first stage transconductance amplifier TCA1 and the second stage transduction amplifier TCA2 are both class A output stages, and the first stage transduction amplifier TCA1, the second stage transconductance amplifier TCA2 and third stage amplifier TSA3 amplifier The series are connected in series by direct coupling. That is to say, there is no capacitor between the first stage transconductance amplifier TCA1, the second stage transduction amplifier TCA2 and the third stage amplifier TSA3 amplifier, so the size between the transistors must be specially designed when designing the circuit. The ratio, in this way, can improve the sensitivity of the overall transimpedance amplifier to temperature and different process processes.

In addition, referring to FIG. 1, the feedback circuit FB in this embodiment includes a bipolar junction transistor B1 and a resistor network RC. The emitter of the bipolar junction transistor B1 is electrically connected to the input current source Iin, and the base and collector of the bipolar junction transistor B1 are connected to the output terminal of the third stage amplifier TSA3. In addition, the resistor network RC is connected in parallel to the bipolar junction transistor B1, and includes a bridged T-shaped network composed of three resistors R1 R R3 and a capacitor C1, wherein one end of the capacitor C1 is electrically Connected to a bridged T-shaped network with the other end of capacitor C1 grounded. Further, the feedback circuit FB can increase the gain of the transimpedance amplifier 1 of the embodiment. The bipolar junction transistor B1 in the feedback circuit FB is used to clamp the third output signal TIAp to stabilize the third output signal TIAp. .

[Another embodiment of a transimpedance amplifier]

In order to explain the circuit design of the transimpedance amplifier of the present invention in more detail, an embodiment will be further described below.

In the following embodiments, portions different from the above-described embodiment of Fig. 1 will be described, and the remaining omitted portions are the same as those of the above-described embodiment of Fig. 1. In addition, for the sake of convenience, like reference numerals or numerals indicate similar elements.

Please refer to FIG. 2. FIG. 2 is a circuit diagram of a transimpedance amplifier according to another embodiment of the present invention. The difference between the embodiment shown in FIG. 1 is that, in this embodiment, the transimpedance amplifier 2 further includes a reference voltage circuit, is connected in parallel to the third-stage amplifier TSA3, and includes a constant current unit I', The tri-crystal transistor MP3, the fourth transistor MP4, the sixth transistor MN6, and the resistor R4. As shown in FIG. 2, the constant current unit I' includes a current mirror MR and a bias current source I _Bias . The third transistor MP3, the fourth transistor MP4 and the current mirror MR are connected in parallel with each other, and the drain of the fourth transistor MP4 forms an output terminal of the reference voltage circuit REF to output the reference voltage signal TIAn. In addition, one end of the resistor R4 is electrically connected to the drain and the gate of the sixth transistor MN6, and the other end of the resistor R4 is electrically connected to the output end of the reference voltage circuit REF.

As with the embodiment shown in FIG. 1, the first-stage transconductance amplifier TCA1 and the second-stage transduction amplifier TCA2 of the present embodiment are both Class A output stages, and the third stage amplifier TSA3 has a Class A output stage. With the class AB output stage, it can combine the advantages of class A output stage and class AB output stage in circuit design. That is, the components of the first output stage OUT1 maintain the on state, providing better linearity, and at the same time, the second output stage OUT2 can further improve the power efficiency of the third stage amplifier TSA3. Similarly, the first stage transconductance amplifier TCA1, the second stage transduction amplifier TCA2 and the third stage amplifier TSA3 amplifier of the embodiment are also connected in series by direct coupling, and the size ratio between the transistors It is specially designed to improve the sensitivity of the overall transimpedance amplifier to temperature and process.

In addition, the circuit design of the feedback circuit FB in this embodiment is the same as the feedback circuit in the embodiment shown in FIG. 1, and similarly, the feedback circuit FB can increase the transimpedance amplifier 2 of the embodiment. The gain of the bipolar junction transistor B1 in the feedback circuit FB can clamp the third output signal TIAp to stabilize the effect of the third output signal TIAp.

[Another embodiment of a transimpedance amplifier]

In order to explain the circuit design of the transimpedance amplifier of the present invention in more detail, an embodiment will be further described below.

In the following embodiments, portions different from the above-described embodiment of Fig. 2 will be described, and the remaining omitted portions are the same as those of the above-described embodiment of Fig. 2. In addition, for the sake of convenience, like reference numerals or numerals indicate similar elements.

Please refer to FIG. 3. FIG. 3 is a circuit diagram of a transimpedance amplifier according to another embodiment of the present invention. The difference from the embodiment shown in FIG. 2 above is that in the transimpedance amplifier 3 of the present embodiment, the reference voltage circuit REF further includes a fifth transistor MP5. The fifth transistor MP5 is connected in parallel to the constant current unit I' and is electrically connected to the supply voltage The source Vcc is between the output terminal of the constant current unit I'.

4A and FIG. 4B, FIG. 4A is a graph of a reference voltage signal as a function of temperature in the transimpedance amplifier provided in the embodiment of FIG. 2, and FIG. 4B is an implementation of FIG. The graph of the reference voltage signal as a function of temperature in the transimpedance amplifier provided in the example.

When the temperature is -40 degrees C to 125 degrees C, shown in Figure 4A, in Figure 4A, the curve shows the variation in V _m transimpedance amplifier TIAp 3 of the third output signal at a low potential due to the temperature caused by The curve V _M shows that the third output signal TIAp of the transimpedance amplifier 3 is caused by temperature at a high potential, and Ref1 shows the change of the reference voltage signal due to temperature. On the other hand, as shown in FIG. 4B, in FIG. 4B, curve V _m shows a third transimpedance amplifier output signal TIAP 3 at a low potential due to the change in temperature caused by the curve V _M 3 shows a transimpedance amplifier The third output signal TIAp changes due to temperature at a high potential, and Ref2 shows the change in the reference voltage signal due to temperature.

4A and FIG. 4B, the voltage change rate of the reference voltage signal of the reference voltage circuit REF in the embodiment shown in FIG. 3 is approximately equal to or equal to the voltage change rate of the third output signal TIAp, but The voltage change rate of the reference voltage signal of the reference voltage circuit REF in the embodiment shown in FIG. 2 is not.

Further, the reference voltage circuit REF in the embodiment illustrated in FIG. 3 additionally sets the fifth transistor MP5 and the fifth transistor, compared to the reference voltage circuit REF in the embodiment illustrated in FIG. 2 . The MP5 is connected in parallel with the constant current unit I', and is electrically connected between the supply voltage source Vcc and the output end of the constant current unit I', so that the reference voltage can be compensated by compensating for the voltage change caused by the temperature change. The voltage change rate of the signal is approximately equal to or equal to the voltage change rate of the third output signal to achieve the effect of stabilizing the reference voltage signal.

It should be noted that, as in the embodiment illustrated in FIG. 1 and FIG. 2, the first-stage transduction amplifier TCA1 and the second-stage transduction amplifier TCA2 of the present embodiment are also Class A output stages, and third. Stage amplifier TSA3 also has Class A output stage and AB Class output stage, so it can combine the advantages of class A output stage and class AB output stage in circuit design. That is, the components of the first output stage OUT1 maintain the on state, providing better linearity, and at the same time, the second output stage OUT2 can further improve the power efficiency of the third stage amplifier TSA3. Similarly, the first stage transconductance amplifier TCA1, the second stage transduction amplifier TCA2 and the third stage amplifier TSA3 amplifier of the embodiment are also connected in series by direct coupling, and the size ratio between the transistors It is specially designed to improve the sensitivity of the overall transimpedance amplifier to temperature and process.

In addition, the circuit design of the feedback circuit FB in this embodiment is the same as the feedback circuit FB in the embodiment shown in FIG. 1 and FIG. 2, and similarly, the feedback circuit FB can increase the embodiment. The AC gain of the transimpedance amplifier 3, wherein the bipolar junction transistor B1 in the feedback circuit FB can clamp the third output signal TIAp to stabilize the effect of the third output signal TIAp.

[Possible effects of the examples]

In summary, the transimpedance amplifier proposed in the embodiment of the present invention is provided with a third-stage amplifier composed of a first output stage and a second output stage, wherein the circuit design of the first output stage belongs to the class A output. The circuit design of the second output stage belongs to the class AB output stage. In this way, the transimpedance amplifier can have the advantages of both the class A amplifier and the class AB amplifier, thereby shortening the transmission delay time of the transimpedance amplifier. On the other hand, in the reference voltage circuit of the transimpedance amplifier proposed in the embodiment of the present invention, the fifth electro-crystal system is disposed in parallel with the constant current unit, and is electrically connected to the output end of the supply voltage source and the constant current unit. In order to improve the instability of the reference voltage signal due to temperature changes or different process methods.

The above description is only an embodiment of the present invention, and is not intended to limit the scope of the invention.

1‧‧‧Transistor Amplifier

Iin‧‧‧ input current source

Is‧‧‧current source

TCA1‧‧‧First Stage Transconductance Amplifier

TCA2‧‧‧Second stage transconductance amplifier

TSA3‧‧‧3rd stage amplifier

OUT1‧‧‧ first output stage

OUT2‧‧‧second output stage

TIAp‧‧‧ third output signal

MN1‧‧‧First NMOS transistor

MN2‧‧‧Second NMOS transistor

MP2‧‧‧second PMOS transistor

FB‧‧‧ feedback circuit

RC‧‧‧Resistor Network

B1‧‧‧Bipolar junction transistor

C1‧‧‧ capacitor

R1, R2, R3‧‧‧ resistors

Vcc‧‧‧ supply voltage source

Claims (5)

A transimpedance amplifier comprising: a first stage transconductance amplifier having an input end and an input end, wherein an input end of the first stage transduction amplifier is electrically connected to an input current source to receive a first input signal And outputting a first output signal from the output end of the first-stage transduction amplifier; a second-stage transduction amplifier having an input end and an input end, wherein the input end of the second-stage transduction amplifier is electrically connected The output of the first stage transconductance amplifier is configured to receive the first output signal, and the output end of the second stage transduction amplifier outputs a second output signal; and a third stage amplifier having an input end And an output end, the input end of the third stage amplifier is electrically connected to the output end of the second stage transconductance amplifier to receive the second output signal, and the output end of the third stage amplifier outputs a third An output signal; a feedback circuit, one end of which is electrically connected to the input end of the first-stage transconductance amplifier, and the other end of which is electrically connected to the output end of the third-stage amplifier to stabilize the third output signal, the feedback The circuit includes: a dual polarity junction transistor, the emitter is electrically connected to the input current source, the base and the collector are connected to the output of the third stage amplifier; and a resistor network is connected in parallel The bipolar junction transistor; wherein the third stage amplifier comprises: a first output stage, the first output stage comprises a current source, the current source is electrically connected to a supply voltage source and the third stage amplifier And a second output stage comprising a first NMOS transistor and a second PMOS transistor, the first NMOS transistor being connected to the gate of the second PMOS transistor to form the third stage Input of the amplifier, the second a source of the PMOS transistor is electrically connected to the supply voltage source, and a drain of the second PMOS transistor is connected to a drain of the first NMOS transistor to an output end of the third stage amplifier, and the The drain of the first NMOS transistor is grounded. The transimpedance amplifier of claim 1 wherein the resistor network is a bridged T-shaped network and a capacitor, the bridged T-shaped network comprising three resistors, one end of the capacitor Electrically connected to the bridged T-shaped network, and the other end of the capacitor is grounded. The transimpedance amplifier of claim 1, wherein the first stage transconductance amplifier, the second stage transconductance amplifier and the third stage amplifier are connected in series by direct coupling. The transimpedance amplifier of claim 1, further comprising a reference voltage circuit connected in parallel to the third stage amplifier, wherein the reference voltage circuit comprises a certain current unit, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor and a resistor; wherein the constant current unit comprises a current mirror and a bias current source, the fifth transistor is connected in parallel to the constant current unit and electrically connected to the Between the supply voltage source and the output end of the reference voltage circuit, one end of the resistor is electrically connected to the source and the gate of the sixth transistor, and the other end of the resistor is electrically connected to the reference voltage circuit The third transistor, the fourth transistor and the current mirror are connected in parallel with each other, and the drain of the fourth transistor forms an output end of the reference voltage circuit to output a reference voltage signal. The transimpedance amplifier of claim 4, wherein the voltage change rate of the reference voltage signal is approximately equal to or equal to a voltage change rate of the third output signal.