JPH0370930B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplifier circuit, and more particularly, to an amplifier circuit that makes it possible to extract a plurality of outputs with different amplification gains from one input.

In various audio devices such as auto-reverse tape recorders, several types of output signals with different signal amplitudes are extracted from one input, and each signal is sometimes used as an audio output or a control signal for various built-in circuits. In such a case, it is necessary to install a plurality of amplifiers with different amplification gains for one input, and to provide an amplifier circuit that outputs several types of amplified outputs.

FIG. 1 shows a conventional amplifier circuit that can obtain two outputs for one input. That is, a differential amplifier 2 is installed in the signal input section, transistors 4 and 6 having a common emitter are installed in the differential amplifier 2, and a voltage is connected between the emitter of each transistor 4 and 6 and a reference potential point. A constant current source 8 is installed. Input terminals 10 and 12 for supplying signals to be amplified are formed at the bases of the transistors 4 and 6, respectively, and current inversion circuits 14 and 16 are provided between the collectors of the transistors 4 and 6 and the power supply terminal 13. ing. Current inversion circuit 14 is transistor 1
8, 20 and resistors 22, 24, 26,
The transistor 18 has a diode configuration, and the transistors 18 and 20 constitute a current mirror circuit. Further, the current inverting circuit 16 is composed of transistors 28, 30 and resistors 32, 34, 36, and the transistor 30 is composed of a diode.
Transistors 28 and 30 constitute a current mirror circuit.

In order to extract first and second amplified outputs having different amplification gains, the first and second amplifiers 3
8,40 are installed. The first amplifier 38 includes transistors 42, 44 and resistors 46, 48, 5.
The base of transistor 42 is shared with the bases of transistors 18 and 20, and the base of transistor 44 is shared with the bases of transistors 28 and 30. Output terminals 54 and 56 are formed at the collectors of each transistor 42 and 44, respectively.
The first amplified output is taken out from between 4 and 56.

The second amplifier 40 is composed of a differential amplifier including transistors 58 and 60 with common emitters, resistors 62 and 64, and a constant current source 66.
The base of the transistor 58 is the same as the transistor 2.
The base of the transistor 60 is connected to the collector of the transistor 20. Output terminals 68 and 70 are formed at the collectors of each transistor 58 and 60, and a second amplified output is taken out between these output terminals 68 and 70.

When the amplifier circuit is configured in this way, the amplifiers 38 and 40 are formed individually, which complicates the circuit configuration and increases the area on the semiconductor substrate constituting the integrated circuit. 6
The existence of 6 becomes a problem.

Therefore, the present invention aims to simplify the circuit configuration, reduce the chip area when configured with an integrated circuit, and create an amplifier circuit that can take out multiple outputs with different amplification gains from one input. For the purpose of providing.

That is, the amplifier circuit of the present invention includes a differential amplifier 71 in which first and second transistors 72 and 74 having a common emitter are installed, and an input signal to be amplified is applied to the first and second transistors.
A diode-connected third transistor 88 is installed on the collector side of the first transistor of the differential amplifier, and a fourth transistor 92 has a common base with the third transistor.
is installed, and a collector current corresponding to the base input of the transistor flows into the first transistor, and a diode-connected fifth transistor 102 is installed on the collector side of the second transistor of the differential amplifier. Sixth transistor 1 whose base is shared with the fifth transistor
06 is installed, a collector current corresponding to the base input is applied to the base of the second transistor, and a collector current according to the base input is applied to the base of the second transistor, and
current inverting circuits 84 and 86 that take out the first output from the transistor or both transistors, and seventh and eighth transistors 118 and 120 that have a common emitter.
is installed, the base of the seventh transistor is shared with the base of the third transistor, the base of the eighth transistor is shared with the base of the fifth transistor, and the base of the seventh transistor is shared with the base of the fifth transistor. It is equipped with an output amplifier (differential amplifier 116) from which a second output is taken out from the collector side of the eighth transistor.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the amplifier circuit of the present invention. A differential amplifier 71 is connected to the input section of this amplifier circuit.
This differential amplifier 71 includes first and second transistors 72 and 7 having a common emitter.
4 and a constant current source 76 connected between the emitter and a reference potential point. Input terminals 78 and 80 are formed at the bases of each transistor 72 and 74, respectively, and a power supply terminal 82 is formed at the collector of each transistor 72 and 74 and a power supply terminal 82 to which a drive voltage Vcc is applied.
Current inversion circuits 84 and 86 are individually provided between the two. In this case, each current inversion circuit 84,
Reference numeral 86 constitutes an output circuit that inverts the current flowing through each transistor 72, 74 and also takes out the first amplified output. That is, the current inversion circuit 8
4 is the third transistor 88, transistor 9
0, fourth transistor 92 and resistor 94,9
6 and 98, and an output terminal 100 is formed at the collector of the transistor 92. The bases of transistors 88 and 92 are shared, and the base and collector of transistor 88 are short-circuited between the emitter and base of transistor 90, so that transistor 88 is diode-connected and the collector of transistor 90 is connected to a reference potential point. It is connected. That is, transistors 88, 90
and 92 constitute a current mirror circuit.
Further, the current inverting circuit 86 is connected to the fifth transistor 1
02, a transistor 104, a sixth transistor 106, and resistors 108, 110, and 112, and an output terminal 114 is formed at the collector of the transistor 106. This current reversal circuit 8
The configuration of 6 is the same as the configuration of the current inversion circuit 84.

In order to take out the second amplified output, a differential amplifier 116 is provided as an output amplifier, and this differential amplifier 116 is connected to the seventh transistor 11.
8. Eighth transistor 120 and resistor 122,
It consists of 124 and 126. The collector of each transistor 118, 120 has an output terminal 12.
8, 130 are formed, and the current inverting circuit 84,
A second amplified output having a different amplification gain from the output of 86 is taken out.

The operation will be explained based on the above configuration. When an input signal is applied to each input terminal 78, 80 of the differential amplifier 71, the current flowing through each transistor 72, 74 changes in response to this input signal, and this current change is applied to the current inverting circuit 84, 86. It will be done. Based on this current change, transistor 9
2,106 collector current changes, output terminal 1
A first amplification output having a constant amplification gain corresponding to the input signal is generated between 00 and 114.

Further, the transistor 88 of the current inverting circuit 84,
92 and the base of the transistor 118 of the differential amplifier 116 are shared, a change in the current of the current inversion circuit 84 changes the base current of the transistor 118, and a change in the current of the current inversion circuit 84 changes the base current of the transistor 118. Based on the current change, the collector current of the transistor 120 also changes, and each output terminal 12
An amplified output based on the amplification gain of the differential amplifier 116 is generated between 8 and 130. That is,
The input signals applied to the input terminals 78 and 80 are amplified separately in the current inverting circuits 84 and 86 or the differential amplifier 116, and outputs based on different amplification gains are sent to the output terminals 100 and 114.
Or occurs at 128,130.

Further, in this case, each transistor 88, 92,
118, and transistors 106, 102, 1
20 have a common base, and when configured as an integrated circuit, the circuit configuration can be simplified, that is, it can be made more compact. In particular, when the amplifier circuit is configured in this way, the bias current of the differential amplifier 116 is
Since it is shared with the base of 106, it is stably supplied, and the outputs generated at output terminals 128 and 130 are stabilized. Further, since each of the component transistors forms a pair, the temperature characteristics of each element cancel each other out, and the temperature characteristics are improved.

In addition, inversion current matching resistors 94, 96, 10 are inserted on the emitter side of each transistor 88, 92, 102, 106 of the current inversion circuits 84, 86.
By adjusting the values of 8 and 110, the amplification gain of the differential amplifier 116 can be set arbitrarily. In particular, with such a configuration, the constant current source 66 in the conventional circuit shown in FIG. 1 is omitted, thereby simplifying the circuit configuration and reducing the chip area when configured as an integrated circuit. .

In this embodiment, the transistors 92 and 106 of the current inverting circuits 84 and 86 are installed individually, but as shown in FIG. By connecting the transistors 92 and 106 to the current inversion circuits 84 and 82, a differential amplifier can be constructed using the transistors 92 and 106 that constitute the current inversion circuits 84 and 86, respectively. In this way, the amplification gain can be freely set with respect to the differential amplifier 116.

In the case of the embodiment, two amplified outputs are set for one input, but it is also possible to install two or more amplifiers and take out two or more outputs with different amplification gains.

As explained above, according to the present invention, it is possible to simplify the circuit configuration, and it is also possible to stably obtain two or more amplified outputs for one input. The area on the substrate can be reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional amplifier circuit, FIG. 2 is a circuit diagram showing an embodiment of the amplifier circuit of the present invention, and FIG. 3 is a circuit diagram showing another embodiment of the invention. 71... Differential amplifier, 72... First transistor, 74... Second transistor, 84, 86
... Current inversion circuit, 88 ... Third transistor, 92 ... Fourth transistor, 102 ... Fifth transistor, 106 ... Sixth transistor, 116 ... Differential amplifier (output amplifier), 11
8...Seventh transistor, 120...Eighth transistor.

Claims (1)

[Claims] 1. A differential amplifier in which first and second transistors having a common emitter are installed, and an input signal to be amplified is applied to the first and second transistors; A third transistor diode-connected to the collector side of the first transistor is installed, a fourth transistor having a common base with the third transistor is installed, and the base input is connected to the first transistor. A fifth transistor diode-connected is installed on the collector side of the second transistor of the differential amplifier, and a sixth transistor has a common base with the fifth transistor. a current inverting circuit in which a transistor is installed, which flows a collector current according to its base input into the second transistor, and takes out a first output from the fourth transistor, the sixth transistor, or both; and a common emitter. seventh and eighth transistors are installed, the base of the seventh transistor is common to the base of the third transistor, and the base of the eighth transistor is common to the base of the fifth transistor. and an output amplifier that is shared by the seventh and eighth transistors, and a second output is taken out from the collector side of the seventh and eighth transistors.