CN1925317A

CN1925317A - AB kind amplifier

Info

Publication number: CN1925317A
Application number: CN 200510098559
Authority: CN
Inventors: 周莉; 吴小晔; 许萍
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2005-09-02
Filing date: 2005-09-02
Publication date: 2007-03-07
Anticipated expiration: 2025-09-02
Also published as: CN100461625C

Abstract

This invention discloses one mobile communication AB amplifier, which comprises AB output electrode voltage tracer and one assistant amplifier, wherein, the assistant amplifier comprises the following parts: N shape comparing device A101 and N shape comparing device A102; one bias circuit and one output electrode composed of PMOS tube AMP1 and one NMOS tube AMN1 and output end of A102 is connected to bias circuit input end; PMOS tube AMP1 source electrode is connected to VDD; grating is connected to output end of A101; leakage electrode and NMOS tube AMN 1 leakage are connected; the NMOS tube AMN1 grating electrode is connected to the output end of bias circuit.

Description

Class ab ammplifier

Technical field

The present invention relates to a kind of amplifier, particularly relate to a kind of class ab ammplifier, this amplifier has slew rate (slew rate) fast.

Background technology

In casacade multi-amplifier, generally comprise voltage amplifier and power amplifier, the effect of voltage amplifier is the amplitude that improves input signal without distortion, to drive the power amplifier of back; The effect of power amplifier improves power output.The AB power-like amplifier is low in energy consumption, and the efficient height can satisfy certain distortion, is widely used in the output stage of circuit.

The voltage follower that typically has an AB class output stage as shown in Figure 1.Voltage amplifier A is the amplifier of typical structure, and PMOS pipe FMP1 and NMOS pipe FMN1 constitute AB class output stage, and biasing circuit provides suitable bias current to output stage.

The voltage follower that typically has AB class output stage obtains slew rate fast if desired, and AB class output stage needs the quiescent current of several mA, thereby is not suitable for low consumption circuit, such as portable product and handheld mobile device etc.

Summary of the invention

The objective of the invention is to overcome the shortcoming that is not suitable for low consumption circuit that prior art exists, in the hope of proposing a kind of class ab ammplifier, it has slew rate and advantage low in energy consumption fast.

The operation principle of class ab ammplifier of the present invention obtains slew rate fast for work when input voltage changes significantly thereby increase quiescent current, does not reduce power consumption thereby do not work when input voltage does not have saltus step.

A kind of class ab ammplifier that the present invention proposes comprises the voltage follower that has AB class output stage, it is characterized in that:

Also comprise a booster amplifier, described booster amplifier is connected in parallel with the voltage follower that has AB class output stage;

Described booster amplifier comprises N type comparator A101 and A102, and biasing circuit and one are by PMOS pipe AMP1 and 1 output stage that NMOS pipe AMN1 constitutes;

The output S1 of comparator A102 is connected with the input of biasing circuit; The source electrode of PMOS pipe AMP1 is connected with VDD, and grid is connected with the output S2 of comparator A101, and drain electrode is connected with the drain electrode of NMOS pipe AMN1; The grid of NMOS pipe AMN1 is connected with the output S3 of biasing circuit, and source electrode is connected with ground.AMP1 and AMN1 are operated in linear zone.

The structure of N type comparator A101 and A102 comprises 4 PMOS pipe MP1, MP2, MP3, MP4 as shown in Figure 3; Two NMOS pipes MN1, MN2 and bias current sources.The source electrode of MP1 is connected with power supply, and grid is connected with the grid of MP2; Drain electrode is connected with the source electrode of MP2; The grid of MP2 is connected with drain electrode, and drain electrode is connected with the drain electrode of MN1; The source electrode of MN1 is connected with the input of bias current sources, and grid is the normal phase input end of comparator; The source electrode of MP3 is connected with power supply, and grid is connected with the grid of MP1, and drain electrode is connected with the source electrode of MP4; The grid of MP4 is connected with the grid of MP1, and drain electrode is connected with the drain electrode of MN2; The source electrode of MN2 is connected with the input of bias current sources, and grid is the negative-phase input of comparator.MP1, MP3 and MP4 are operated in the linear work district, MP2, MN1, MN2 is operated in the saturation region.

The class ab ammplifier that adopts the present invention to propose not only makes amplifier have slew rate fast, and reduces power consumption, is applicable to low consumption circuit.

Description of drawings

Fig. 1 is the voltage follower structure figure that typically has AB class output stage.

Fig. 2 is a class ab ammplifier structure drawing of device of the present invention.

Fig. 3 is the N type comparator configuration figure in the class ab ammplifier of the present invention.

Fig. 4 is the structure chart of device embodiment of the present invention.

Fig. 5 is the slew rate simulation waveform of main amplifier in the embodiment of the invention.

Fig. 6 is the slew rate simulation waveform of the amplifier of embodiment of the invention realization.

Embodiment

Further specify the operation principle and the advantage of this device below in conjunction with the embodiment of device of the present invention.

Fig. 4 is the structure chart of device embodiment of the present invention, and all CMOS pipes are high tension apparatus.

PMOS pipe AMP2 and NMOS pipe AMN2 form biasing circuit, for AMN1 provides suitable bias current.PMOS pipe FMP2 and NMOS pipe FMN2 form biasing circuit, for FMN1 provides suitable bias current.

The size relationship of 4 PMOS pipes is among comparator A101 and the A102:

{(\frac{W}{L})}_{MP 1} = {(\frac{W}{L})}_{MP 2} = \frac{1}{N} {(\frac{W}{L})}_{MP 3} = \frac{1}{N} {(\frac{W}{L})}_{MP 4}

。The size relationship of two NMOS pipes is:

{(\frac{W}{L})}_{MN 1} = {(\frac{W}{L})}_{MN 2}

(W, L are respectively metal-oxide-semiconductor channel width and channel length).

When A101 is operated in DC state (voltage of two inputs equates and do not change that supply voltage does not change), the electric current that flows through two branch roads of comparator equates, because MP1, MP2 and MP3, the asymmetrical relationship of MP4 size makes

(Vds) _MP1+ (Vds) _MP2＞＞(Vds) _MP3+ (Vds) _MP4(Vds is metal-oxide-semiconductor source electrode-drain voltage), thus the output voltage V of comparator made _S2Near supply power voltage, make the AMP1 pipe end.In like manner the AMN1 pipe also ends in the DC operating state.Thereby the quiescent dissipation of output stage is 0.

When handling small-signal, same because MP1, MP2 and MP3, the asymmetrical relationship of MP4 size make MP1, and MP3 and MP4 are operated in the linear work district, and the gain of comparator is very little, less than 5.V _S2With bias voltage voltage V _S3Deficient change with AMP1 and AMN1 conducting.The quiescent dissipation of output stage is 0.

When handling large-signal, two kinds of situations are arranged:

A kind of is to jump to high voltage when input voltage or supply voltage by low-voltage, A101 comparator work this moment, output voltage V _S2Jump to low level by high level, the AMP1 pipe conducting in the output stage is charged to load, when the output voltage rising equates with input voltage, and V _S2Rising makes the AMP1 pipe end;

Another kind is to jump to low-voltage when input voltage or supply voltage by high voltage, A102 comparator work this moment, output voltage V _S1Jump to low level by high level, bias voltage V _S3To high level, make the AMN1 conducting by low transition, for load provides discharge path, when output voltage drops to when equating with input voltage V _S1Rising makes V _S3Reduce, AMN1 ends.

So thereby booster amplifier increases the electric current that load is discharged and recharged and has obtained fast slew rate when handling large-signal.

Fig. 5 is the slew rate simulation waveform that typically has the voltage follower of AB class output stage.

Fig. 6 is the slew rate simulation waveform of the class ab ammplifier of embodiment of the invention realization.

Relatively both slew rates as can be seen, by booster amplifier in parallel, slew rate can be increased to 41 kilovolts/second by 1.4 kilovolts/second.

The booster amplifier of P type structure is also at this patent protection range.

Claims

1, a kind of class ab ammplifier comprises the voltage follower that has AB class output stage, it is characterized in that:

Described booster amplifier comprises N type comparator (A101) and N type comparator (A102), a biasing circuit and an output stage that is made of PMOS pipe (AMP1) and 1 NMOS pipe (AMN1);

The output (S1) of comparator (A102) is connected with the input of biasing circuit; The source electrode of PMOS pipe (AMP1) is connected with VDD, and grid is connected with the output (S2) of comparator (A101), and drain electrode is connected with the drain electrode of NMOS pipe (AMN1); The grid of NMOS pipe (AMN1) is connected with the output (S3) of biasing circuit, and source electrode is connected with ground.

2, class ab ammplifier according to claim 1 is characterized in that:

Described N type comparator comprises that PMOS pipe (MP1), PMOS manage (MP2), PMOS pipe (MP3) and PMOS pipe (MP4) and NMOS pipe (MN1), NMOS pipe (MN2) and an inclined to one side value current source;

The source electrode of PMOS pipe (MP1) is connected with power supply, and grid is connected with the grid of PMOS pipe (MP2); Drain electrode is connected with the source electrode of PMOS pipe (MP2); The grid of PMOS pipe (MP2) is connected with drain electrode, and drain electrode is connected with the drain electrode of NMOS pipe (MN1); The source electrode of NMOS pipe (MN1) is connected with the input of bias current sources, and grid is the normal phase input end of comparator; The source electrode of PMOS pipe (MP3) is connected with power supply, and grid is connected with the grid of PMOS pipe (MP1), and drain electrode is connected with the source electrode of PMOS pipe (MP4); The grid of PMOS pipe (MP4) is connected with the grid of PMOS pipe (MP1), and drain electrode is connected with the drain electrode of NMOS pipe (MN2); The source electrode of NMOS pipe (MN2) is connected with the input of bias current sources, and grid is the negative-phase input of comparator.

3, class ab ammplifier according to claim 1 and 2 is characterized in that, PMOS pipe (AMP1) and NMOS pipe (AMN1) in the described booster amplifier all are operated in linear zone.

4, class ab ammplifier according to claim 2 is characterized in that:

PMOS pipe (MP1) in the described N type comparator, PMOS pipe (MP3) and PMOS pipe (MP4) are operated in linear zone, and PMOS pipe (MP2), NMOS pipe (MN1) and NMOS pipe (MN2) are operated in the saturation region.

5, class ab ammplifier according to claim 1 is characterized in that:

Described booster amplifier can also adopt the comparator of P type structure.