CN217689889U

CN217689889U - Voltage follower

Info

Publication number: CN217689889U
Application number: CN202220786092.0U
Authority: CN
Inventors: 杨思平; 赵雷
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-03-29
Filing date: 2022-03-29
Publication date: 2022-10-28
Anticipated expiration: 2032-03-29

Abstract

The utility model provides a voltage follower, include: an output circuit connected to the signal terminal, the output circuit configured to amplify a signal input from the signal terminal; and the feedback circuit is respectively connected with the output end and the input end of the output circuit, and is configured to regulate the quiescent current output by the output circuit. The utility model discloses can solve the great problem of harmonic distortion.

Description

Voltage follower

Technical Field

The utility model relates to an integrated circuit designs technical field, concretely relates to voltage follower.

Background

The output part of the existing transistor class AB audio power amplifier mostly adopts a multi-stage composite voltage follower, and a composite tube composed of a plurality of transistors generally plays a role. Therefore, a plurality of PN junctions are generally arranged between the base electrode (B) and the emitter electrode (E) of the composite tube. This results in a relatively large pressure difference between the output and the input of the composite tube (BE) and, due to its significant non-linear characteristics, a large harmonic distortion.

SUMMERY OF THE UTILITY MODEL

In view of this, embodiments of the present invention are directed to providing a voltage follower, which can solve the problem of large harmonic distortion.

According to the utility model discloses an aspect, the utility model discloses a voltage follower that embodiment provided, include: an output circuit connected to the signal terminal, the output circuit configured to amplify a signal input from the signal terminal; and the feedback circuit is respectively connected with the output end and the input end of the output circuit, and is configured to regulate the quiescent current output by the output circuit.

In one embodiment, the output circuit includes: the input end of the first triode circuit is respectively connected with the signal end and the output end of the feedback circuit; the input end of the second triode circuit is connected with the output end of the first triode circuit; and the input end of the field effect transistor circuit is connected with the output end of the second triode circuit, and the output end of the field effect transistor circuit is connected with the input end of the feedback circuit.

In one embodiment, the voltage follower further comprises: an emitter resistor connected to an input terminal of the second triode circuit, the emitter resistor configured to stabilize the quiescent current on the input terminal side of the second triode circuit; and the grid resistor is connected with the input end of the field effect transistor circuit.

In one embodiment, the feedback circuit includes: a third triode circuit connected to an output of the output circuit, the third triode circuit configured to feed back an output voltage; a fourth triode circuit connected to an output of the output circuit, the fourth triode circuit configured to feed back a bias voltage.

In an embodiment, the voltage follower further comprises: a mirror current source, the mirror current source respectively with the input of first triode circuit, the input of third triode circuit is connected, the mirror current source with output circuit's output is connected, output circuit's output includes field effect transistor circuit's output, the mirror current source structure is: and providing stable current for the first triode circuit and the third triode circuit.

In one embodiment, a plurality of first resistors are included between the mirror current source and the output terminal of the output circuit, and the plurality of first resistors are connected in series.

In one embodiment, the voltage follower further comprises: and the bias circuit is respectively connected with the input ends of the first triode circuit and the second triode circuit, and is also connected with the input end of the field effect transistor circuit.

In one embodiment, the bias circuit includes a plurality of bias resistors; and one part of the bias resistor is connected with the input end of the second triode circuit in series, and the other part of the bias resistor is connected with the input end of the field effect transistor circuit in series.

In one embodiment, the first triode circuit includes: the emitting electrode of the triode Q3 and the emitting electrode of the triode Q4 are respectively connected with the signal end; the second triode circuit comprises: the collector of the triode Q3 and the collector of the triode Q4 are respectively connected with the base of the triode Q5 and the base of the triode Q6; and the field effect transistor circuit comprises: the field-effect transistor M1 and the field-effect transistor M2, the collecting electrode of the triode Q5 and the collecting electrode of the triode Q6 are respectively connected with the grid electrode of the field-effect transistor M1 and the grid electrode of the field-effect transistor M2.

In one embodiment, the third transistor circuit includes: the base electrode of the triode Q7 and the base electrode of the triode Q8 are respectively connected with the output end of the output circuit; the capacitor C1 and the capacitor C2 are respectively connected with a collector electrode of the triode Q7 and a collector electrode of the triode Q8; and the fourth triode circuit comprises: the base electrode of the triode Q1 and the base electrode of the triode Q2 are respectively connected with one end of the capacitor C1 and one end of the capacitor C2; the base electrode of the triode Q1 and the base electrode of the triode Q2 are respectively connected with the base electrode of the triode Q3 and the base electrode of the triode Q4.

The embodiment of the utility model provides a voltage follower, the component is less, then carries out bias voltage's feedback through output voltage, realizes that the difference between output voltage and the input voltage reduces, and harmonic distortion also consequently diminishes to the system can keep a very low static consumption, can solve the great problem of voltage follower harmonic distortion.

Drawings

The above and other objects, features and advantages of the present application will become more apparent by describing in more detail embodiments of the present application with reference to the attached drawings. The accompanying drawings are included to provide a further understanding of the embodiments of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings, like reference numbers generally represent like parts or steps.

Fig. 1 is a schematic structural diagram of a voltage follower according to an exemplary embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Further, in the exemplary embodiments, since the same reference numerals denote the same components having the same structure or the same steps of the same method, if an embodiment is exemplarily described, only a structure or a method different from the already described embodiment is described in other exemplary embodiments.

Throughout the specification and claims, when one element is described as being "connected" to another element, the one element may be "directly connected" to the other element or "electrically connected" to the other element through a third element. Furthermore, unless explicitly described to the contrary, the term "comprising" and its corresponding terms should only be taken as including the stated features, but should not be taken as excluding any other features.

Fig. 1 is a schematic structural diagram of a voltage follower provided in an exemplary embodiment of the present application, and as shown in fig. 1, the voltage follower includes: an output circuit 100, the output circuit 100 being connected to the signal terminal, the output circuit 100 being configured to amplify a signal input from the signal terminal; and a feedback circuit 200, wherein the feedback circuit 200 is respectively connected with the output end and the input end of the output circuit 100, and the feedback circuit 200 is configured to regulate the quiescent current output by the output circuit 100.

The voltage follower is a simple circuit structure, can play the role of impedance matching, and when a weaker signal is used for driving a relatively higher current load, the voltage follower can be added in the middle to improve the strength of the signal, improve the load capacity and simultaneously ensure that the waveform and the amplitude of the signal are unchanged. The output circuit 100 in the voltage follower may include a plurality of transistors, and the weak varying electrical signal may be amplified into an electrical signal with a large amplitude by the transistors, so that the transistors may perform the function of amplifying the amplitude of the signal. The feedback circuit 200 is connected to the output circuit 100, and the feedback circuit 200 is configured to adjust the quiescent current output by the output circuit 100 by adjusting the bias voltage of the system through the current output by the output circuit 100, and then input the quiescent current into the output circuit 100 again to adjust the output voltage and the input voltage of the voltage follower, so as to reduce the difference between the output voltage and the input voltage, thereby achieving the effect of low-distortion output.

In one embodiment, the output circuit may include: the input end of the first triode circuit is respectively connected with the signal end and the output end of the feedback circuit; the input end of the second triode circuit is connected with the output end of the first triode circuit; and the input end of the field effect transistor circuit is connected with the output end of the second triode circuit, and the output end of the field effect transistor circuit is connected with the input end of the feedback circuit.

Taking one of the first triode circuit, the second triode circuit and the field effect transistor circuit as an example, a signal is input from an emitter of the first triode to form a common base amplification circuit, the signal flows through the second triode and then drives the field effect transistor backwards, an output end (drain electrode) of the field effect transistor is an output end of the final voltage follower, and the first triode, the second triode and the field effect transistor form an output circuit. The weakly varying electrical signal may be amplified by the triode to an electrical signal with a large amplitude, so that the triode may function to amplify the amplitude of the signal. The field effect transistor can also be used for amplifying signals, and because the input impedance of the field effect transistor amplifier is very high, the coupling capacitor can have smaller capacity, an electrolytic capacitor is not needed, and the field effect transistor can also be conveniently used as a constant current source.

As shown in fig. 1, the transistor Q3 and the transistor Q4 may represent a first transistor, the transistor Q5 and the transistor Q6 may represent a second transistor, and the field effect transistor M1 and the field effect transistor M2 may represent field effect transistors.

In an embodiment, the voltage follower may further include: an emitter resistor connected to an input terminal of the second triode circuit, the emitter resistor configured to stabilize a quiescent current at an input terminal side of the second triode circuit; and the grid resistor is connected with the input end of the field effect transistor circuit.

The emitter resistor is connected to the input terminal of the second triode circuit and is arranged to generate a negative feedback current signal. The Ube voltage of the triode generally decreases along with the increase of the temperature, the result is that the current of the amplification side (namely an emitter) increases to generate amplification drift, and once the current increases after an emitter resistor is introduced, the Ure also increases to increase the voltage of a base terminal, so that the Ib is reduced, and the current of the emitter is naturally reduced, namely the amplification drift caused by the temperature is reduced by introducing the current negative feedback resistor, and a certain stabilizing effect is exerted on the quiescent current. The grid resistance can eliminate grid oscillation, a capacitive structure is arranged between grid emitting (or grid source) electrodes of the insulated gate device, parasitic inductance of a grid loop is unavoidable, and if the grid resistance does not exist, the grid loop generates strong oscillation under the excitation of a driver driving pulse, so that a resistor must be connected in series to quickly attenuate, and the stability is improved.

As shown in fig. 1, the resistors R7 and R8 may represent emitter resistors, and the resistors R11 and R12 may represent gate resistors. The resistor R7 is connected with the emitter of the triode Q5 in series, the resistor R8 is connected with the emitter of the triode Q6 in series, the resistor R11 is connected with the grid of the field-effect tube M1 in series, and the resistor R12 is connected with the grid of the field-effect tube M2 in series.

In an embodiment, the feedback circuit may include: a third triode circuit connected with the output end of the output circuit, the third triode circuit being configured to feed back the output voltage; and the fourth triode circuit is connected with the output end of the output circuit and is constructed to feed back the bias voltage.

The output voltage in the output circuit can be fed back through the third triode circuit, and the bias voltage in the system can be fed back through the fourth triode circuit and the diode in the feedback circuit. The bias voltage is a voltage to be set between the base and the emitter and between the collector and the base when the transistor is in an amplification state in the transistor amplifier circuit. Because the PN junction between the base and emitter of the transistor should be forward biased and the PN junction between the collector and base should be reverse biased to place the transistor in an amplifying state.

For example, as shown in fig. 1, the output signal of the output circuit 100 is output through the diode D1 and the diode D2, so that the connection point between the resistor R13 and the resistor R14 can be regarded as the input point of the feedback circuit 200, which is equivalent to the output end of the output circuit 100, and after the resistor R13 and the resistor R14 are connected to this point, the voltages of the resistor R13 and the resistor R14 are output to the transistor Q1 and the transistor Q2, from the output end of the output circuit 100 to the emitters of the transistor Q1 and the transistor Q2, and then fed back to the bases of the transistor Q3 and the transistor Q4 from the emitters of the transistor Q1 and the transistor Q2. Complete feedback of the signal is formed, and the feedback enables the whole circuit to be changed into a follower with the voltage gain of 1.

In addition, taking resistor R13 as an example, the voltage across resistor R13 and resistor R14 reflects the back electrode current in the static state, the voltage across resistor R13 discharges capacitor C1 through resistor R15, resistor R17, transistor Q7 and through diode D5, and capacitor C1 forms a current across transistor Q1 through resistor R2. And in a static state, the transistor Q1 and the transistor Q3 can be regarded as a mirror current source, so that the current of the transistor Q1 is set as the current of the transistor Q3. The feedback of the triode Q7 and the triode Q8 can be used for stabilizing the quiescent current of the output end, the upper part of the output current passes through the diode D5, the lower part passes through the diode D6, the voltage of the capacitor C1 and the capacitor C2 is adjusted, the voltage of the capacitor C1 and the capacitor C2 acts on the triode Q1 and the triode Q2, partial offset of results of the triode Q3 and the triode Q4, the field effect tube M1 and the field effect tube M2 is formed, and the direct-coupled circuit is formed from the triode Q3 and the triode Q4, so that the offset of the whole system can be adjusted by adjusting the feedback circuit part.

In an embodiment, the voltage follower may further include: the mirror current source, the mirror current source is connected with the input of first triode circuit, third triode circuit respectively, and the mirror current source is connected with output circuit's output, and output circuit's output includes field effect transistor circuit's output, and the mirror current source structure is: and supplying stable current for the first triode circuit and the third triode circuit.

The mirror current source may provide a suitable bias current for the amplifier stage and determine the quiescent operating point. The mirror current source is arranged to provide constant current bias for the first triode circuit and the third triode circuit, and the influence on the circuits when certain external factors (such as temperature) change can be overcome. And the mirror current source does not need to be fast and therefore consumes less power.

In one embodiment, the mirror current source output circuit includes a plurality of first resistors connected in series between the output terminals.

There are a plurality of first resistances between the output of mirror current source and output circuit, a plurality of first resistances are connected in series, and a fourth triode, the mirror current source is connected with the input of first triode circuit, the input of third triode circuit respectively.

As shown in fig. 1, the resistor R13, the resistor R14, the resistor R15, the resistor R16, the resistor R17, the resistor R18, the resistor R19, and the resistor R20 may all represent first resistors, and taking the resistor R13 as an example, in a static state, the voltage on the resistor R13 discharges the capacitor C1 through the resistor R15, the resistor R17, the transistor Q7, and the diode D5, and the capacitor C1 forms a current on the transistor Q1 through the resistor R2. In addition, the transistor Q1 and the transistor Q3 can be regarded as a mirror current source in a static state, and the same current can be formed on the transistor Q3 by forming the current on the transistor Q1, so that the current provided with the transistor Q1 is equal to the current provided with the transistor Q3. The mirror current source is arranged to provide constant current bias for the first triode and the third triode, and the influence on the circuit when certain external factors (such as temperature) change can be overcome. And the mirror current source does not need to be fast and therefore consumes less power.

In an embodiment, the voltage follower may further include: and the biasing circuit is respectively connected with the base electrodes of the first triode and the second triode and is also connected with the source electrode of the field effect transistor.

In order to ensure that the transistor can work normally, a common resistor is added into the amplifying circuit, direct current power supply voltage is introduced, and the biasing circuit is respectively connected with the base electrodes of the first triode and the second triode to provide base voltage and base current IB for the transistor (the first triode and the second triode), namely the biasing circuit is added outside the transistor circuit. The feedback circuit is used for carrying out bias voltage feedback, so that the difference value between the output voltage and the input voltage is extremely small, and the effect of low-distortion output is achieved.

In one embodiment, the bias circuit includes a plurality of bias resistors; wherein, one part of the bias resistor is connected with the input end of the second triode circuit in series, and the other part of the bias resistor is connected with the input end of the field effect transistor circuit in series.

As shown in fig. 1, the resistors R5 and R6 may represent bias resistors, and the current of the transistor Q3 flows through the resistors R5 and R6 to form a bias. The resistor R9 and the resistor R10 may also represent bias resistors, and the current of the transistor Q5 or the transistor Q6 flows through the resistor R9 and the resistor R10 to form a bias.

In one embodiment, as shown in fig. 1, the first triode circuit includes: the emitting electrode of the triode Q3 and the emitting electrode of the triode Q4 are respectively connected with the signal end; the second triode circuit includes: the collector of the triode Q3 and the collector of the triode Q4 are respectively connected with the base of the triode Q5 and the base of the triode Q6; and the field effect transistor circuit includes: the field-effect transistor M1 and the field-effect transistor M2, the collecting electrode of the triode Q5 and the collecting electrode of the triode Q6 are respectively connected with the grid electrode of the field-effect transistor M1 and the grid electrode of the field-effect transistor M2.

The field effect transistor M1 can adopt a P channel enhancement mode field effect transistor, the field effect transistor M2 can adopt an N channel enhancement mode field effect transistor, wherein, the signal level is input by V3, is connected to the emitting electrode of the triode Q3 and the emitting electrode of the triode Q4, then is input to the triode Q5 and the triode Q6 by the triode Q3 and the triode Q4, the field effect transistor M1 and the field effect transistor M2 are respectively driven by the triode Q5 and the triode Q6, the field effect transistor M1 and the field effect transistor M2 are finally output from an OUT port through the diode D1 and the diode D2, and the output circuit 100 is formed.

In one embodiment, as shown in fig. 1, the third transistor circuit includes: the base electrode of the triode Q7 and the base electrode of the triode Q8 are respectively connected with the output end of the output circuit; the capacitor C1 and the capacitor C2 are respectively connected with the collector of the triode Q7 and the collector of the triode Q8; and the fourth triode circuit comprises: the base electrode of the triode Q1 and the base electrode of the triode Q2 are respectively connected with one end of the capacitor C1 and one end of the capacitor C2; the base electrode of the triode Q1 and the base electrode of the triode Q2 are respectively connected with the base electrode of the triode Q3 and the base electrode of the triode Q4.

The input end of the feedback circuit 200 is located at the middle point between the resistor R13 and the resistor R14, and the input end of the feedback circuit 200 is connected to the output end of the output circuit 100, that is, the fet M1 and the fet M2 are output from the middle point between the resistor R13 and the resistor R14 through the diode D1 and the diode D2 in addition to the OUT port, and voltage and current are adjusted through the resistor R13, the resistor R14, the resistor R15, the resistor R16, the resistor R17, the resistor R18, the resistor R19, the resistor R20, the diode D3, the diode D4, and the diode D7, and finally pass through the transistor Q7 and the transistor Q8 and pass through the diode D5 and the diode D6 to the capacitor C1 and the capacitor C2, and in a static state, the capacitor C1 and the capacitor C2 discharge to the transistor Q1 and the transistor Q2 through the resistor R2 and the resistor R3.

The power supply of the system can adopt a power supply of plus or minus 40V, such as V1 and V2 in FIG. 1.

The signal stage and the power amplification stage can be coupled through a resistor-capacitor (a resistor R21 and a capacitor C3), so that the frequency characteristic can be improved, and the self-oscillation of the audio power amplifier can be effectively prevented.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalents and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A voltage follower, comprising:

an output circuit connected to the signal terminal, the output circuit configured to amplify a signal input from the signal terminal;

and the feedback circuit is respectively connected with the output end and the input end of the output circuit, and is configured to regulate the quiescent current output by the output circuit.

2. The voltage follower of claim 1, wherein the output circuit comprises:

the input end of the first triode circuit is respectively connected with the signal end and the output end of the feedback circuit;

the input end of the second triode circuit is connected with the output end of the first triode circuit;

and the input end of the field effect transistor circuit is connected with the output end of the second triode circuit, and the output end of the field effect transistor circuit is connected with the input end of the feedback circuit.

3. The voltage follower of claim 2, further comprising:

an emitter resistor connected to an input terminal of the second triode circuit, the emitter resistor configured to stabilize the quiescent current on the input terminal side of the second triode circuit;

and the grid resistor is connected with the input end of the field effect transistor circuit.

4. The voltage follower of claim 2, wherein the feedback circuit comprises:

a third triode circuit connected to an output of the output circuit, the third triode circuit configured to feed back an output voltage;

a fourth triode circuit connected with an output of the output circuit, the fourth triode circuit configured to feed back a bias voltage.

5. The voltage follower of claim 4, further comprising:

a mirror current source connected to the input of the first triode circuit and the input of the third triode circuit, respectively, the mirror current source being connected to the output of the output circuit, the output of the output circuit including the output of the field effect transistor circuit, the mirror current source being configured to: and providing stable current for the first triode circuit and the third triode circuit.

6. The voltage follower of claim 5, comprising a plurality of first resistors connected in series between the mirror current source and the output of the output circuit.

7. The voltage follower of claim 2, further comprising:

and the bias circuit is respectively connected with the input ends of the first triode circuit and the second triode circuit, and is also connected with the input end of the field effect transistor circuit.

8. The voltage follower of claim 7, wherein the bias circuit comprises a plurality of bias resistors; and one part of the bias resistor is connected with the input end of the second triode circuit in series, and the other part of the bias resistor is connected with the input end of the field effect transistor circuit in series.

9. The voltage follower of claim 2,

the first triode circuit comprises: the emitting electrode of the triode Q3 and the emitting electrode of the triode Q4 are respectively connected with the signal end;

the second triode circuit comprises: the collector of the triode Q3 and the collector of the triode Q4 are respectively connected with the base of the triode Q5 and the base of the triode Q6; and

the field effect transistor circuit includes: the field-effect transistor M1 and the field-effect transistor M2, the collecting electrode of triode Q5, the collecting electrode of triode Q6 respectively with the grid of field-effect transistor M1, the grid of field-effect transistor M2 is connected.

10. The voltage follower of claim 4, wherein the third triode circuit comprises: the base electrode of the triode Q7 and the base electrode of the triode Q8 are respectively connected with the output end of the output circuit;

the capacitor C1 and the capacitor C2 are respectively connected with a collector of the triode Q7 and a collector of the triode Q8; and

the fourth triode circuit comprises: the base electrode of the triode Q1 and the base electrode of the triode Q2 are respectively connected with one end of the capacitor C1 and one end of the capacitor C2;

the base electrode of the triode Q1 and the base electrode of the triode Q2 are respectively connected with the base electrode of the triode Q3 and the base electrode of the triode Q4.