CN201204568Y

CN201204568Y - Audio power amplification circuit

Info

Publication number: CN201204568Y
Application number: CNU2008200595360U
Authority: CN
Inventors: 曾泉
Original assignee: SHANGHAI WEIXI MICROELECTRONICS CO Ltd
Current assignee: SHANGHAI WEIXI MICROELECTRONICS CO Ltd
Priority date: 2008-06-10
Filing date: 2008-06-10
Publication date: 2009-03-04
Anticipated expiration: 2018-06-10

Abstract

The utility model discloses an audio power amplifying circuit, comprising a first power amplifier and a second power amplifier. The output end of the first power amplifier is connected with the input end of the second power amplifier. A mute switch circuit is connected between the first power amplifier and the second power amplifier. The audio power amplifying circuit reduces the design for feedback short circuit switch through the mute switch circuit and good mute effect is achieved.

Description

Audio power amplifying circuit

Technical field

The utility model relates to a kind of amplifying circuit, particularly a kind of audio power amplifying circuit.

Background technology

All integrated quiet controlled function in present many audio power amplifying circuits.As shown in Figure 1, in existing AB class audio power amplifying circuit, it comprises the first power amplifier A1 and the second power amplifier A2 that two push-pull bridge loads (BTL) connect, each power amplifier connects input resistance Rin, feedback resistance Rf, first resistance R 1 respectively, be connected with an input capacitance Cin between input signal end Is and the input resistance Rin, two power amplifier A1, A2 connect respectively a power supply Vdd and its output end vo+, connect a loud speaker Ls between the Vo-.Silent mode mainly is with the very low K switch 1 of conducting resistance, K2 short circuit with the input of the output of power amplifier operational amplifier A 1, A2 and power amplifier operational amplifier A 1, A2, like this at input, even input signal is arranged, because the resistance of above-mentioned negative feedback shorting switch is very low, the gain of input signal is very little or be not exaggerated, thereby makes circuit working at quiet output state.

As shown in Figure 2, on the basis of above-mentioned quiet measure, the method that also has is directly by two other K switch 3, K4 input signal to be disconnected, and is connected on the signal ground Gnd directly two input short circuits to arrive better quiet effect.

The switch resistance that two kinds of above-mentioned circuit structures all require to feed back short circuit is very low, and not only because the conducting resistance of feedback switch is more little, the closed loop gain of the operational amplifier of its signal path is low more for this.Because conducting resistance is more little, operational amplifier is low more to the gain that causes effective differential input signal owing to not matching of device simultaneously.These all require the conducting resistance of switch the smaller the better.But, in present integrated circuit fabrication process, conducting resistance is more little, the size that means switch is big more, and big switch size, meaning at circuit has bigger parasitic capacitance, and this not only can improve the manufacturing cost of integrated circuit, improved stability requirement simultaneously, increased design difficulty circuit working.

The utility model content

The technical problems to be solved in the utility model is in order to overcome the defective that the size of switch is big in the prior art, parasitic capacitance is big, manufacturing cost is high and design difficulty is big, a kind of audio power amplifying circuit is provided, and the designing requirement that this audio power amplifying circuit will feed back short switch reduces and is quiet effective.

The utility model solves above-mentioned technical problem by following technical proposals: a kind of audio power amplifying circuit, it comprises one first power amplifier and one second power amplifier, the output of this first power amplifier is connected with the input of second power amplifier, its characteristics are, are connected with a silence switch circuit between this first power amplifier and second power amplifier.

Wherein, this first power amplifier and second power amplifier all comprise an interconnective folded common source and common grid input stage, a unsteady biasing circuit and a common source output stage, each this common source output stage includes PMOS pipe and NMOS pipe, and this PMOS pipe and NMOS pipe are interconnected to form CMOS pipe.

Wherein, this silence switch circuit comprises one first switch and a second switch, this first switch is controlled the short circuit or the disconnection of the grid of the PMOS pipe in these two power amplifiers, and this second switch is controlled the short circuit or the disconnection of the grid of the NMOS pipe in these two power amplifiers.

Wherein, this first switch is a PMOS pipe, and its source electrode is connected the grid of the PMOS pipe in these two power amplifiers respectively with draining, and its grid connects the first control signal end; This second switch is a NMOS pipe, and its source electrode is connected the grid of the NMOS pipe in these two power amplifiers respectively with draining, and its grid connects the second control signal end.

Positive progressive effect of the present utility model is:

1, to be added in the signal voltage on the loud speaker be homophase to the utility model, and so no matter the input signal of whole power audio amplifier is much, and under mute state, the signal of output is zero, quiet better effects if.

2, adopt audio power amplifying circuit of the present utility model, the designing requirement of above-mentioned described feedback short switch can be reduced, the amplification path that reason comes from difference has on the one hand become common mode (homophase) amplification path, be the high resistant node because be connected the two ends of the switch on the grid in the utility model simultaneously, can design forr a short time than previous feedback switch, thereby reduce design cost and design risk.

3, adopt audio power amplifying circuit of the present utility model, the differential operational amplifier that BTL is connected is operated in the common mode operating state, this means when amplifier need be when changing normal operating conditions over to from quiet, the DC operation state of power amplifier can not change, this makes that the variation of the operating state of the power operational amplifier of existence is avoided in the prior art, thereby avoids unnecessary POP/Click noise.

Description of drawings

Fig. 1 is the schematic diagram of a kind of audio power amplifying circuit in the prior art.

Fig. 2 is the schematic diagram of another kind of audio power amplifying circuit in the prior art.

Fig. 3 is the schematic diagram of audio power amplifying circuit of the present utility model.

Fig. 4 is the schematic diagram of Fig. 3 intermediate power amplifier and silence switch circuit.

Fig. 5 is the schematic diagram of recommending common source power output stage and silence switch circuit.

Fig. 6 A and 6B are the schematic diagram of switch in the silence switch circuit.

Embodiment

Lift a preferred embodiment below, and come the clearer the utility model that intactly illustrates in conjunction with the accompanying drawings.

Fig. 3 is the schematic diagram of audio power amplifying circuit of the present utility model.As shown in Figure 3, the utility model audio power amplifier circuit comprises the first power amplifier A1 and the second power amplifier A2 that two push-pull bridge loads (BTL) connect, the input of the first power amplifier A1 connects an input resistance Rin, be connected with an input capacitance Cin between input signal end Is and the input resistance Rin, the input of the first power amplifier A1 and output end vo+between connect a feedback resistance Rf; The input of the second power amplifier A2 and output end vo-between connect and to connect a silence switch circuit between one first resistance R 1, two power amplifier A1, A2, and its output end vo+, connect a loud speaker Ls between the Vo-.Silent mode is mainly controlled by the silence switch circuit, thereby makes audio power amplifying circuit be operated in quiet output state.The signal of the utility model output end vo+output is that output amplitude equates, phase place is opposite with the signal of another output end vo-output, its connected mode can provide the bigger output signal amplitude of oscillation to load, thereby bigger power output is provided, and the gain of whole power amplifier is by the first power amplifier A1 external input resistance Rin and feedback resistance Rf decision.

Fig. 4 is the schematic diagram of Fig. 3 intermediate power amplifier and silence switch circuit.As shown in Figure 4, each power amplifier A1, A2 comprise an interconnective folded common source and common grid input stage, a unsteady biasing circuit and a common source output stage, each common source output stage includes PMOS pipe MP1, MP2 and a NMOS pipe MN1, MN2, and a PMOS pipe and a NMOS pipe are interconnected to form CMOS pipe.Wherein: the grid of the PMOS pipe MP1 in first operational amplifier A 1 is labeled as A1_PG, and the grid of the PMOS pipe MP2 in second operational amplifier A 2 is labeled as A2_PG; The grid of NMOS pipe MN1 in first operational amplifier A 1 is labeled as A1_NG, and the grid of the NMOS pipe MN2 in second operational amplifier A 2 is labeled as A2_NG.Silence switch circuit and grid A1_PG, A2_PG, A1_NG and A2_NG couple together.

Fig. 5 is the schematic diagram of recommending common source power output stage and silence switch circuit.As shown in Figure 5, the silence switch circuit comprises first K switch 5 and second switch K6, the grid A1_PG of two PMOS pipes of first K switch, 5 controls and short circuit or the disconnection of grid A2_PG, the grid A1_NG of two NMOS pipes of second switch K6 control and short circuit or the disconnection of grid A2_NG.

Fig. 6 A and 6B are the schematic diagram of switch in the silence switch circuit.Shown in Fig. 6 A and 6B, wherein first K switch 5 is a PMOS pipe, and its grid connects the first control signal end Cs1, and its source electrode is connected grid A1_PG and grid A2_PG respectively with drain electrode; Second switch K6 is a NMOS pipe, and its grid connects the second control signal end Cs2, and its source electrode is connected grid A1_NG and grid A2_NG respectively with drain electrode.When system was set to silent mode, the grid potential of PMOS pipe (first K switch 5) was set to low level " 0 ", and the PMOS pipe is connected to form short circuit with grid A1_PG and A2_PG; The grid potential of NMOS pipe (second switch K6) is set to high level " 1 ", and the NMOS pipe is connected to form short circuit with grid A1_NG and A2_NG.When system was set to normal mode of operation, the grid potential of PMOS pipe (first K switch 5) was set to high level " 1 ", grid A1_PG and A2_PG are disconnected the formation open circuit; The grid potential of NMOS pipe (second switch K6) be set to low level " 0 ", grid A1_NG and A2_NG disconnected form open circuit.The effect that adopts this control mode is when system is set to silent mode, the grid of PMOS pipe MP1, MP2 in first operational amplifier A 1 and second operational amplifier A 2 has identical current potential, the grid of NMOS pipe MN1, MN2 also has identical current potential simultaneously, thereby guaranteed the opposite current potential of the output end vo of first operational amplifier A 1+and the output end vo of second operational amplifier A 2-have, the differential signal that is applied to like this on the loud speaker just has been zero, thereby has realized quiet effect.

Though more than described embodiment of the present utility model, but those skilled in the art is to be understood that, these only illustrate, and under the prerequisite that does not deviate from principle of the present utility model and essence, can make numerous variations or modification to these execution modes.Therefore, protection range of the present utility model is limited by appended claims.

Claims

1, a kind of audio power amplifying circuit, it comprises one first power amplifier and one second power amplifier, the output of this first power amplifier is connected with the input of second power amplifier, it is characterized in that, be connected with a silence switch circuit between this first power amplifier and second power amplifier.

2, audio power amplifying circuit as claimed in claim 1, it is characterized in that, this first power amplifier and second power amplifier all comprise an interconnective folded common source and common grid input stage, a unsteady biasing circuit and a common source output stage, each this common source output stage includes PMOS pipe and NMOS pipe, and this PMOS pipe and NMOS pipe are interconnected to form CMOS pipe.

3, audio power amplifying circuit as claimed in claim 2, it is characterized in that, this silence switch circuit comprises one first switch and a second switch, this first switch is controlled the short circuit or the disconnection of the grid of the PMOS pipe in these two power amplifiers, and this second switch is controlled the short circuit or the disconnection of the grid of the NMOS pipe in these two power amplifiers.

4, audio power amplifying circuit as claimed in claim 3 is characterized in that, this first switch is a PMOS pipe, and its source electrode is connected the grid of the PMOS pipe in these two power amplifiers respectively with draining, and its grid connects one first control signal end; This second switch is a NMOS pipe, and its source electrode is connected the grid of the NMOS pipe in these two power amplifiers respectively with draining, and its grid connects one second control signal end.