JPH0159762B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to an amplifier suitable for integration into an integrated circuit that amplifies input signals from two systems.

An amplifier has two input terminals and typically amplifies the input signal from one input terminal (for example, the playback signal from a tape deck or record player) and optionally amplifies the input signal from the other input terminal. One use is to mix and amplify an input signal (for example, an audio signal from an external mask).

The problem with integrated circuits of amplifiers suitable for such applications is that DC coupling must be made from the two input terminals to the commonly used amplifier circuit. It is necessary that there be no fluctuation in the DC bias potential when switching between two states. That is, if a fluctuation occurs in the DC bias potential of the input circuit when switching between two states, the fluctuation is amplified by the subsequent amplifier circuit and appears as a shock sound, giving an unpleasant feeling.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an amplifier that amplifies input signals applied to two input terminals singly or in combination without generating switching shock noise using one amplifier circuit. be.

Hereinafter, the present invention will be explained in detail according to its implementation.

FIG. 1 shows an embodiment of the present invention.
In FIG. 1, the reference numeral 100 surrounded by a dashed line is an integrated circuit as an amplifier, and the reference numeral 200 is a negative feedback power amplification circuit. a and b are input terminals, c is a switching terminal, d is a feedback terminal, e is a ground terminal, f is an output terminal, and g is a power supply terminal. Resistance R ₁₂ ,
A bias current is set by R ₁₃ , transistor Q ₁₃ , and resistor R ₁₁ , and a constant current circuit is configured by diode D ₂ , transistors Q ₂ , Q ₅ , and Q ₁₀ to supply bias to each part. Transistor _Q4 and resistor
The emitter follower circuit made up of _R2 and the constant current circuit made up of transistor _Q3 and resistor _R3 are both biased by transistor _Q2 .
Similarly, the emitter follower circuit consisting of transistor Q ₆ and resistor R ₅ and the constant current circuit consisting of transistor Q ₄ and resistor R ₄ are both biased by transistor Q ₅ . Also, transistor Q ₁₆ and resistor R ₈ and transistor Q ₈
A constant current circuit consisting of a resistor _R7 and a resistor R7 is biased by a transistor _Q10 .

The switching circuit consists of resistors R ₉ , R ₁₀ and transistors
It is composed of Q ₇ , Q ₁₁ and Q ₁₂ . Switch SW connected to switching terminal c is MIX OFF
When the transistors Q ₇ and Q ₁₂ are in the position
Biased by R ₁₀ , it becomes conductive, and transistor Q ₁₁ turns off. As a result, the collector of transistor Q ₅ is grounded, transistors Q ₄ and Q ₆ are turned off, and transistor Q ₈ and transistor Q ₁₆ are turned on. On the other hand, when the switch SW is in the MIX ON position, the bases of transistors Q ₇ and Q ₁₂ are grounded and are turned off, and transistor Q ₁₁ is connected to the resistor
It is biased by R ₉ and becomes conductive. As a result, transistors Q ₄ and Q ₆ are turned on, and transistors Q ₈ and Q ₁₆ are turned off because the collector of transistor Q ₁₀ is grounded.

The transmission circuit consists of diode D ₁ and transistor Q ₉
The cathode of the diode _D1 is connected to the collectors of transistors _Q3 , _Q4 , and _Q8 , and the collector of the transistor _Q9 is connected to the resistor _R15 and the non-inverting input terminal of the negative feedback power amplifier circuit 200. connected to. Also, transistor
_Q9 supplies a bias current to the resistor _R15 and the transistor _Q15 , and the bias potential of the non-inverting input terminal of the negative feedback power amplifier 200 is the same as that of the transistors _Q14 and _Q15.
and resistors R ₁₂ , R ₁₃ , R ₁₄ and R ₁₅ .

The operation of a circuit having such a configuration will be explained.

First, switch SW connected to switching terminal c
When is in the MIX OFF position, the signal from the signal source V _S1 applied to input terminal a is connected to the transistor Q ₁ and the resistor
It is transmitted to diode D ₁ via R ₂ and transistor Q ₃ . Signal source V _S2 applied to input terminal b
The signal is not transmitted to the diode D ₁ because the transistors Q ₅ and Q ₄ are in a damped state due to the conduction of the transistor Q ₇ . As a result, the signal from the signal source V _S1 transmitted to the diode D ₁ is transmitted to the non-inverting input terminal of the negative feedback power amplifier 200 by the current mirror circuit composed of the diode D ₁ and the transistor Q ₉ , and the signal is transmitted to the non-inverting input terminal of the negative feedback power amplifier 200. power amplifier 2
00 and output from the output terminal f.

On the other hand, when the switch SW is in the MIX ON position, the signal from the signal source V _S1 applied to the input terminal a is transmitted to the diode D ₁ in the same manner as described above. The signal of the signal source V _S2 applied to the input terminal b is transmitted to the diode D ₁ since the transistors Q ₆ and Q ₄ are in a conductive state. This makes the diode D ₁
The signals from the signal sources V _S1 and V _S2 are mixed and transmitted to the negative feedback power amplifier 200 by a current mirror circuit including a diode D ₁ and a transistor Q ₉ . After being amplified by the negative feedback power amplification circuit 200, it is output from the output terminal f.

Here, there are two states, namely MIX OFF and
Negative feedback power amplifier 20 in MIX ON state
The bias potential of the 0 non-inverting input terminal is as follows.

First, when the switch SW is in the MIX OFF position, the bias potential V _BI1 of the non-inverting input terminal of the negative feedback power amplifier 200 is expressed by the following equation.

V _BI1 = I _CQ9 ×R ₁₅ +V _BEQ15 +V _BQ15 = I _D1 ×R ₁₅ +V _BEQ15 +V _BQ15 ……… I _D1 = I _CQ3 +I _CQ8 ……… I _CQ3 = (V _BQ3 −V _BEQ3 )/R ₃ … … I _CQ8 = (V _BQ8 − V _BEQ8 ) / R ₇ ……… V _BQ8 = I _CQ10 × R ₂ + V _BQ16 ……… However, ID ₁ : Current of diode D ₁ I _CQ3 , I _CQ8 , I _CQ9 , I _CQ10 :Transistors Q ₃ , Q ₈ ,
Collector currents of Q ₉ , Q ₁₀ V _BEQ3 , V _BEQ8 , V _BEQ15 : Transistors Q ₃ , Q ₈ ,
Base-emitter voltage of Q ₁₅ V _BQ3 , V _BQ8 , V _BQ15 , V _BQ16 : Transistor Q ₃ ,
Base potential of Q ₈ , Q ₁₅ , Q ₁₆ Next, the bias potential V _B12 of the non-inverting input terminal when the switch SW is in the MIX ON position is expressed by the following equation.

V _BI2 = I _D1 ×R ₁₅ +V _BEQ15 +V _BQ15 ……… I _D1 = I _CQ3 +I _CQ4 ……… I _CQ4 = (V _BQ4 −V _BEQ4 )/R ₄ ……… V _BQ4 = I _CQ5 ×R ₅ +V _BQ6 ...... However, I _CQ4 , I _CQ5 : Collector current V of transistors Q ₄ , Q _{5 BEQ4} : Base-emitter voltage of transistor Q ₄ V _BQ4 , V _BQ6 : Base potential of transistors Q ₄ , Q ₆ Here, In the formula and formula, the transistor
Since Q ₅ and Q ₁₀ are transistors of the same shape and form a current mirror circuit, I _CQ5 = I _CQ10 ,
Transistor Q ₆ and transistor Q ₁₆ have the same shape, and resistors R ₆ and R ₁₆ have the same value, so V _BQ16 = V _BQ6 . Also, since resistors R ₅ and R ₈ have the same value, R ₅ =
R ₈ , so V _BQ8 = V _BQ4 . Also, in equations and equations, transistors Q ₄ and Q ₈ have the same shape, and resistors R ₄ and R ₇ have the same value, so V _BEQ4 =
V _BEQ8 , R ₄ = R ₇ , and I _CQ4 = I _CQ8 . From this, V _BI1 = V _B12 in the equations and equations, and the bias potential of the non-inverting input terminal of the negative feedback power amplifier circuit 200 is the same regardless of whether the switch SW is in the MIX OFF or MIX ON position, and the two states are equal. There is no change due to switching. Therefore, no shock noise is generated due to switching.

As described above, according to the present invention, an input circuit is realized in which signals applied to two input terminals are amplified by one negative feedback power amplifier circuit, either singly or in combination, without generating switching shock noise. can.

Next, FIG. 2 shows another embodiment of the present invention.

In the embodiment shown in FIG. 2, the present invention is used to construct a two-channel power amplifier that can easily switch between a dual amplifier function and a BTL amplifier function.

In FIG. 2, 100 surrounded by a broken line is an integrated circuit, and 200 and 300 are the same negative feedback power amplifier. h is the feedback terminal of the negative feedback power amplifier 300, i is the feedback terminal for BTL, j is the output terminal of the negative feedback power amplifier 300, and the switches SWa,
SWb and SWc are linked. Further, elements or terminals having the same symbols as in FIG. 1 indicate the same elements.

To explain the circuit operation, first, when switch SWa connected to switching terminal c is in the Dual position,
Transistors Q ₇ , Q ₁₂ , Q ₂₄ and Q ₃₁ are in a conductive state,
Transistors Q ₁₁ and Q ₁₉ are turned off, transistors Q ₄ and Q ₆ are turned off, and transistors Q ₁₇ and Q ₂₀ are turned on. At this time,
The signal applied to input terminal a from signal source V _S1 is
The signal is transmitted to the diode D ₁ via the transistors Q ₁ and Q ₃ , and is transmitted to the negative feedback power amplifier circuit 200 by a transmission circuit constituted by a current mirror circuit of the diode D ₁ and the transistor Q ₉ . There, it is further amplified and output from the output terminal f to the load R _L2 . Further, the signal applied to input terminal b from the signal source V _S2 is transmitted to the diode D ₃ via the emitter follower circuit composed of the transistor Q ₁₇ and the resistor R ₁₃ and the transistor Q ₂₀ , and is transmitted to the diode D ₃
A negative feedback power amplification circuit 300 is created by a transmission circuit consisting of a current mirror circuit of transistor _Q23 and
transmitted to. There, it is further amplified and output from output terminal j to load R _L3 . Thereby, integrated circuit 100 operates as a dual amplifier.

On the other hand, when the switches SWa, SWb, and SWc are in the BTL position, the switching terminal c is grounded, the transistors Q ₇ , Q ₁₂ , Q ₂₄ , and Q ₃₁ are turned off, and the transistors Q ₁₁ and Q ₁₉ are turned on. As a result, transistors Q ₄ , Q ₆ and Q ₃₂ become conductive, and transistors Q ₁₇ and Q ₂₀ become inactive. At this time,
The signal applied to input terminal a by signal source V _S1 is transmitted to diode D ₁ in the same way as above.
Further, the signal applied to the input terminal b by the signal source V _S2 is transmitted to the diode D ₁ via the transistors Q ₆ and R ₄ and mixed with the signal from the signal source V _S1 . Then, a negative feedback power amplifier circuit 2 is created by a transfer circuit consisting of a diode _D1 and a transistor _Q9 .
00, amplified, and output from the output terminal f. Furthermore, the signal appearing at the output terminal f is transmitted to the BTL feedback terminal i via the resistor 30 and the transistor Q ₂₀ , is attenuated by the resistor 30 and the feedback resistor Rf ₂ , and is sent to the negative feedback power amplifier 30 from the feedback terminal h.
0. The signal is then amplified and output from output terminal j as an inverted output. This causes the load
Output signals with mutually inverted phases are applied to both ends of R _L1 , and the integrated circuit 100 operates as a BTL amplifier.

Here, the bias potentials of the non-inverting input terminals of the negative feedback power amplifiers 200 and 300 will be explained. First, the bias potential of the non-inverting input terminal of the negative feedback power amplifier 200 is determined by the collector currents of the transistors Q ₃ , Q ₄ and Q ₅ as described in the embodiment of FIG.
It is affected by I _CQ3 , I _CQ4 , and I _CQ8 , but since it is set so that I _CQ4 = I _CQ8 , Dual or BTL
The bias potential does not change when switching.

Next, the bias potential of the non-inverting input terminal of the negative feedback power amplifier circuit 300 is determined by the base potential V _BQ30 of the transistor Q ₃₀ and the base-emitter voltage of the transistor Q ₃₀ , as in the case of the negative feedback power amplifier circuit 200 described above. It is determined by V _BEQ30 and the voltage drop across resistor R ₂₇ due to collector current I _CQ28 of transistor Q ₂₈ , R ₂₇ ×I _CQ28 . Here, transistor Q ₂₈ and diode D ₃ form a current mirror circuit, so the collector current of transistor Q ₂₈ I _CQ28
is equal to the current I _D3 of diode D ₃ , and the current I D3 of diode D ₃ is equal to the current I _D3 of transistors Q ₂₀ , Q ₂₁ and Q ₂₅
is determined by the respective collector currents I _CQ20 , I _CQ21 and I _CQ25 . That is, when the switch SWa is in the Dual position, transistors Q ₁₇ and Q ₂₀ are on, transistors Q ₂₁ and Q ₂₃ are off, and I _D3 =
I _CQ20 + I _CQ25 , and when switch SWa is in the BTL position, conversely, transistors Q ₁₇ and Q ₂₀ are in the off state, and transistors Q ₂₁ and Q ₂₃ are in the conductive state.
I _D3 = I _CQ21 + I _CQ25 . Here, as already described in the embodiment of FIG.
Transistors Q ₁₇ and _{Q 23 ,} Q ₂₀ and Q _{21 ,} and resistors R ₆ and R ₃₂ , R ₁₈ and R 22 , R ₂₀ and R so that the collector currents I _CQ20 and I _CQ21 of Q 20 and Q ₂₁ are equal. Since the shape and resistance value of ₂₁ are set, I _CQ20 = I _CQ21 . For this reason, if the switch SWa is Dual or
The current I _D3 of the diode D ₃ does not change regardless of the position of the BTL, and therefore the bias potential of the non-inverting input terminal of the negative feedback power amplifier circuit 300 does not change. From these, in both negative feedback power amplifier circuits 200 and 300, Dual or BTL
No shock sound is generated when switching.

As described above, according to the present invention, it is also possible to provide a two-channel power amplifier that can easily switch between the dual amplifier function and the BTL amplifier function without generating switching shock noise.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. FIG. 2 is a circuit diagram showing another embodiment according to the present invention. 100...Integrated circuit, 200, 300...Negative feedback power amplifier, V _S1 , V _S2 ... Signal source, _Q1 to _Q32 ...
...Transistor, D ₁ ~ _{D 3} ... Diode, R ₁ ~
R ₃₄ ...Resistance, R _f1 ~ R _f2 ... Feedback resistance, R _L1 ~ _{R L3}
...Load resistance, _C1 to _C4 ...Capacitor, a...
Input terminal, b...Input terminal, c...Switching terminal,
d...Feedback terminal, e...Ground terminal, f...Output terminal, g...Power supply terminal, h...Feedback terminal, i...
...Feedback terminal for BTL, j...Output terminal, SW,
SWa～SWc……Switch.

Claims (1)

[Claims] 1 A first circuit having a first signal input terminal and outputting a current according to a first input signal supplied to this terminal.
a second input circuit that has a second signal input terminal and outputs a current according to a second input signal supplied to this terminal; It has a current source circuit that outputs a current set equal to the output current, and a switching control terminal, and when this terminal is in a first state, the second input circuit is cut off and a current is generated at its output. a switching control circuit that cuts off the current source circuit and prohibits generation of current at its output when the switching control terminal is in a second state, the first and second input circuits, and the current source; The output of the circuit has an input that is commonly connected, and outputs a current according to the sum of the output currents of the first and second input circuits or the sum of the output currents of the first input circuit and the current source circuit. What is claimed is: 1. An amplifier comprising: a transmission circuit that transmits a signal; and an amplifier circuit that receives an output current from the transmission circuit.