CN100505542C

CN100505542C - Mute circuit of audio frequency amplifier

Info

Publication number: CN100505542C
Application number: CNB2004100941707A
Authority: CN
Inventors: 林伟程
Original assignee: Princeton Technology Corp
Current assignee: Princeton Technology Corp
Priority date: 2004-12-29
Filing date: 2004-12-29
Publication date: 2009-06-24
Anticipated expiration: 2024-12-29
Also published as: CN1797949A

Abstract

The invention discloses design of mute circuit of audio amplifier. Differential pairs of differential amplifier are copied. Two groups of MOS semiconductor switch control the differential pair respectively. Both of two groups of differential pair are connected to MOS semiconductor of forming current mirror circuit. Two groups of MOS semiconductor switch contrl on / off of first differential pair and second differential pair. Through an inverter, a mute signal controls one group of MOS semiconductor switch. Through two inverters, the mute signal controls another group of MOS semiconductor switch. Thus, the mute signal can turn on / off of the first differential pair and the second differential pair so as to form effect of mute control.

Description

Mute circuit of audio frequency amplifier

Technical field

The present invention relates to the mute circuit of audio frequency amplifier design, relate in particular to and duplicate the differential of differential amplifier, and design with the mute circuit of audio frequency amplifier that two groups of MOS semiconductor switchs are controlled to (differential pair).

Background technology

With reference to figure 1, the mute circuit design diagram of general audio frequency amplifier is shown, on the audio path of audio frequency amplifier, add a pair of cmos switch M1, M2, M1 is NMOS, M2 is PMOS.Audio frequency V _InThe drain electrode of input cmos switch M1, M2, and export next stage amplifier OP4 generation output signal V to by the source electrode of cmos switch M1, M2 _OutMute signal M ₀Control the grid of M1, M2 respectively through two inverter INV5 and INV6, and control a bias switch M3, as shown in the figure.

As mute signal M ₀During for " 1 " (high potential) (promptly carrying out quiet), cmos switch M1, M2 open circuit, M3 conducting, audio frequency V at this moment _InBlockaded fixed-bias transistor circuit V _ReferenceThen therefore input amplifier OP4 forms quiet effect.Its equivalent electric circuit as shown in Figure 2.

As mute signal M ₀During for " 0 " (electronegative potential) (promptly not quiet), cmos switch M1, M2 conducting, M3 then opens circuit, at this moment audio frequency V _InSend into amplifier OP4 by cmos switch M1, M2, its equivalent electric circuit as shown in Figure 3, cmos switch M1, M2 become a resistor R _OnSo M3 is inoperative because of opening circuit, the input impedance of amplifier OP4 is R _i, the input signal V of amplifier OP4 as a result _i=V _In* R _i/ (R _On+ R _i).

With reference to figure 4, the resistance characteristic of cmos switch M1, M2 is shown.R _M1The characteristic curve that the resistance of expression switch M1 changes along with voltage, R _M2The characteristic curve that the resistance of expression switch M2 changes along with voltage, R _OnExpression switch M1, the combined resistance characteristic curve of M2 when small signal.Because R _M1, R _M2, R _OnAll change, so V along with change in voltage _iNaturally also along with R _OnVariation and change, make V _InSignal produce distortion, so the design of cmos switch M1, M2 is undesirable.

Summary of the invention

Therefore the purpose of this invention is to provide a kind of mute circuit of audio frequency amplifier design, duplicate the differential of differential amplifier, and controlled respectively with two groups of MOS semiconductor switchs to (differential pair).Two groups differential to all joining with the MOS semiconductor that forms current mirroring circuit.

Two groups of MOS semiconductor switchs control respectively first differential to and the second differential right startup or close.One mute signal is through an inverter controlling one group of MOS semiconductor switch wherein; This mute signal and through another group MOS semiconductor switch of two inverter controlling, thus mute signal can make first differential to or second differential to starting or close, thereby form the effect of quiet control.

These two groups of MOS semiconductor switchs are formed by three MOS semiconductors, altogether six MOS semiconductors.

First group of MOS semiconductor switch with a MOS semiconductor as the first differential right power supply supply intermediary, and with second, third MOS semiconductor accept this mute signal control through the control of this inverter a MOS semiconductor power supply is supplied first differential right.

Second group of MOS semiconductor switch with the 4th MOS semiconductor as the second differential right power supply supply intermediary, and with the 5th, the 6th MOS semiconductor accept this mute signal control through the control of these two inverters the 4th MOS semiconductor power supply is supplied second differential right.

Description of drawings

Fig. 1 is the mute circuit design diagram of general audio frequency amplifier.

Fig. 2 is the schematic equivalent circuit of the general mute circuit of audio frequency amplifier when mute signal is high potential.

Fig. 3 is the schematic equivalent circuit of the general mute circuit of audio frequency amplifier when mute signal is electronegative potential.

Fig. 4 illustrates the resistance characteristic figure of cmos switch.

Fig. 5 illustrates general differential amplifier circuit figure.

Fig. 6 illustrates the mute circuit of audio frequency amplifier of the present invention.

Fig. 7 illustrates the schematic equivalent circuit of mute circuit of audio frequency amplifier of the present invention when mute signal is high potential.

Fig. 8 illustrates the schematic equivalent circuit of mute circuit of audio frequency amplifier of the present invention when mute signal is electronegative potential.

Embodiment

With reference to general differential amplifier circuit figure shown in Figure 5.Illustrate PMOS M41, M42 become one group differential to (differential pair), NMOS M43 and M44 then constitute one group of current mirror.Audio frequency V _InInput M42 produces output signal V at M41 _Out

The present invention utilizes the general differential amplifier circuit of Fig. 5, designs the mute circuit of the audio frequency amplifier of the present invention of Fig. 6.Have among Fig. 6 two groups differential to Diff_1, Diff_2, all link to each other with current mirroring circuit M43, M44, Diff_1 is made up of original PMOSM41, M42, Diff_2 then is made up of PMOS M51, M52.Diff_1 and V _In, V _OutLink to each other, Diff_2 then with bias voltage V _Reference, V _OutLink to each other.

The present invention differentially designs two groups of switching circuit SW_1 and SW_2 respectively above to Diff_1, Diff_2 at two groups, and with mute signal M0 through two inverter INV5 and INV6 control switch circuit SW_1 and SW_2 respectively, as shown in the figure.Switching circuit SW_1 and SW_2 be control circuit Diff_1 and Diff_2 respectively.Switching circuit SW_1 is made up of PMOS M53, M54, M57, and switching circuit SW_2 is made up of PMOS M55, M56, M58.PMOS M57, M58 become the V of Diff_1, Diff_2 respectively _CcThe supplier.

As mute signal M ₀During for " 1 " (high potential), the M53 conducting, M54 opens circuit, so fixed-bias transistor circuit V _BiasCan't deliver to the grid of M57, M57 opens circuit, and makes V _CcCan't supply with Diff_1, Diff_1 does not work, so V _InCan't produce V _OutSo, form quiet effect.And M55 opens circuit M56 conducting, so V _BiasDeliver to the grid of M58 and conducting M58 makes V _CcSupply with Diff_2, therefore make Diff_2 work.In this case, equivalent electric circuit of the present invention is one desirable differential to operational amplifier as shown in Figure 7 basically, and its input is without any resistance, V _ReferenceDeliver to input, form quiet effect.

As mute signal M ₀During for " 0 " (electronegative potential), M53 opens circuit, M54 conducting, so fixed-bias transistor circuit V _BiasDeliver to the grid of M57 and conducting M57, with V _CcSupply with Diff_1, make Diff_1 work, so V _InImport and generation V _OutThe M55 conducting, M56 opens circuit, and M58 is opened circuit, V _CcCan't supply to give Diff_2, so Diff_2 can not work.In this case, equivalent electric circuit of the present invention is one desirable differential to operational amplifier as shown in Figure 8 basically, its input is without any resistance, because SW_1 and SW_2 form with the MOS switching circuit, resistance is almost nil during conducting, and resistance is almost infinity when opening circuit.So just avoided that cmos switch M1, M2 are inserted in V in the prior art _InAnd between the amplifier, form and change R with voltage _OnEffect.

Spirit of the present invention and scope only are subject to following claim, are not subject to the foregoing description.

Claims

1. mute circuit of audio frequency amplifier, comprise a basic differential amplifier circuit, it is first differential right that it is with first pair of MOS semiconductor that main body becomes, and join respectively with the second pair of MOS semiconductor that forms current mirroring circuit, these first differential two right grids are the input and the output of audio frequency amplifier;

It is second differential right that the 3rd pair of MOS semiconductor becomes, and also joins respectively with the second pair of MOS semiconductor that forms current mirroring circuit; These second differential two right grids then connect a bias voltage and output respectively;

In addition two groups of MOS semiconductor switchs control respectively first differential to and the second differential right startup or close;

One mute signal is through an inverter controlling one group of MOS semiconductor switch wherein, this mute signal and through another group MOS semiconductor switch of two inverter controlling, therefore mute signal can make first differential to or second differential to starting or close, thereby form the effect of quiet control.

2. mute circuit of audio frequency amplifier as claimed in claim 1, wherein these two groups of MOS semiconductor switchs are formed by three MOS semiconductors, altogether six MOS semiconductors;

In first group of MOS semiconductor switch, semi-conductive first utmost point of one the one MOS connects that this is first differential right, in order to control this first differential right startup or to close, supply intermediary as this first differential right power supply, the semi-conductive grid of the one MOS connects semi-conductive first utmost point of one the 2nd MOS and semi-conductive second utmost point of one the 3rd MOS, semi-conductive second utmost point of the one MOS and semi-conductive second utmost point of the 2nd MOS are connected to a set voltage, to control the semi-conductive startup of a MOS or to close, semi-conductive first utmost point of the 3rd MOS connects a fixed-bias transistor circuit, and common this mute signal that connects through this inverter of the 2nd MOS semiconductor and the semi-conductive grid of the 3rd MOS, by controlling the semi-conductive startup of a MOS or close, it is first differential right that power supply is supplied to; And

In second group of MOS semiconductor switch, semi-conductive first utmost point of the 4th MOS connects that this is second differential right, in order to control this second differential right startup or to close, supply intermediary as this second differential right power supply, the semi-conductive grid of the 4th MOS connects semi-conductive first utmost point of one the 5th MOS and semi-conductive second utmost point of one the 6th MOS, semi-conductive second utmost point of the 4th MOS is connected this set voltage with semi-conductive second utmost point of the 5th MOS, in order to control the semi-conductive startup of the 4th MOS or to close, semi-conductive first utmost point of the 6th MOS connects this fixed-bias transistor circuit, and common this mute signal that connects through these two inverters of the 5th MOS semiconductor and the semi-conductive grid of the 6th MOS, by controlling the semi-conductive startup of the 4th MOS or close, it is second differential right that power supply is supplied to.