JPS58115930A - Electronic switching amplifier circuit - Google Patents

Abstract

PURPOSE:To realize an electronic switching amplifier circuit which amplifies an arbitrary input signal out of input signals to a lot of input terminals with an arbitrary gain, with a comparatively simple circuit. CONSTITUTION:An output signal is picked up at an output terminal 3 through an amplifier 14. Since the output signal is fed back to each differential circuit with negative feedback circuits consisting respectively of resistors 38, 39;40, 41;42, 43 and 44, 45 provided depending on input differential circuits, the gain between the input and output to a signal to an input terminal 26 depends on the resistors 38, 39, the gain to a signal to an input terminal 27 depends on the resistors 40, 41, the gain to a signal to an input terminal 28 depends on the resistors 42, 43 and the gain of a signal to an input terminal 29 depends on the resistors 44, 15 respectively. An arbitrary gain is set at each input terminal by selecting the value of the resistors 38-45.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic switching amplifier circuit, and provides an electronic switching amplifier circuit that can amplify only one arbitrary signal among a plurality of input signals with an arbitrary fu gain. It is.

FIG. 1 shows an example of a conventional electronic switching circuit. The circuit consists of a differential circuit consisting of transistors 8.9 and 10.
11, an amplifier circuit 14 which uses the output of the differential circuit pair as a common input, and a common negative circuit for negative feedback of the output of the amplifier circuit 14 to the differential circuit pair. Resistor 16.17 and control terminal 4.6 forming a feedback circuit
It consists of a pair of transistors 12 and 13 which are alternately activated and deactivated by the signal . Note that 16 is a load resistance.

In such a circuit, the input signals applied to input terminals 1 and 2 are selected based on the operation of transistors 12 and 13.

In other words, only the input signal to the differential circuit whose emitter is connected to the collector of one of the operating transistors 12 and 13 is selected and output to the load resistor 15 and input to the amplifier circuit 14. and output to the output terminal 3 as an output signal. For example, when the operation 13 of the transistor 12 is stopped, only the signal to the input terminal 1 of the differential circuit consisting of the transistors 8 and 9 connected to the collector of the transistor 12 is taken out as an output signal to the output terminal 3; The signal to the input terminal 2 of the differential circuit consisting of the transistors 10 and 11 connected to the collector of the stopped transistor 3 is not output to the output terminal 3.

By the way, in such a conventional circuit, since the differential circuit is a pair, only one pair of input terminals can be set, and the input signal is
There is a drawback that selection is impossible when there are more than one species. Furthermore, since the negative feedback circuit is common to both differential circuits, the gain between the input signal and the output signal is uniquely determined by the value of the resistor 16.17, and is the same value for the input signals to input terminals 1 and 2. It also has the disadvantage that it is impossible to apply it to circuits that require different gains.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such drawbacks and provide an amplifier circuit that can amplify any input signal out of any number of input signals with any gain.

FIG. 2 shows an example of a circuit according to the present invention. In Figure 2, 18 and 19, 20 and 21.22 and 23°24 and 25
are a pair of transistors forming a differential circuit. terminal 26
．． 27, 28, and 29 are four input terminals respectively provided in the four differential circuits mentioned above. The input signals to the input terminals 26 to 29 are applied to the control terminals 30.31 and 32.33, so that only any one of the transistors 30 to 33 is fully activated, and the rest are completely stopped. As a result, it is selectively taken out to the output terminal 3. That is, if only one of the transistors 30 to 33 is brought into full operation, only the differential circuit connected to its collector will be brought into full operation, and the remaining differential circuits will be completely stopped. As a result, only the input signal to the input terminal connected to the fully operational differential circuit is selected and becomes the output signal to the load 15 of the differential circuit. This output signal passes through the amplifier circuit 14 and is taken out to the output terminal 3 as an output signal. The output signal is generated by resistors 38, 39, 40, 41, 42, 43, 44, and 4 provided for each input differential circuit.
6, the gain between the input and output for the signal to the input terminal 26 is set by the resistors 38 and 39, and the gain between the input and output for the signal to the input terminal 27 is set by the resistor 40. 41. The gain for the signal to input terminal 28 is determined by resistors 42 and 43 . The gain for the signal to input terminal 29 will be determined by resistors 44 and 15, respectively. Therefore, by selecting the values of the resistors 38 to 45, any gain value can be set for each input terminal.

For example, if the transistor 34 is in a fully operational state and the transistors 31 to 33 are in a completely stopped state by the signals from the control terminals 30 to 33, then a differential circuit consisting of transistors 18 and 19 connected to the →rector of the transistor 34 only transistor 31 is fully operational, while transistor 31
The three sets of differential circuits made up of transistors 20, 21, 22, 23, 24, and 25 whose emitters are commonly connected to the collectors of transistors 21, 23, 24, and 25 are completely stopped.

Therefore, only the signal applied to the input terminal 26 is transmitted to the output terminal 3.
The signals taken out as output signals to and applied to the input terminals 27 to 29 will not be output as output signals. Furthermore, since only the differential circuit of transistors 18 and 19 is in operation, the negative feedback circuit consisting of resistors 38 and 39 is effective, and the value of resistor 38 is set to R38, and the value of resistor 39 is set to R39.
An arbitrary value can be determined without being affected by the path.

As described above, according to the present invention, it is possible to realize, with a relatively simple circuit, an electronic switching amplifier circuit that can amplify only an arbitrary signal with an arbitrary gain among signals input to a large number of input terminals. It is extremely useful for simplifying electronic equipment and improving its reliability.

Although the above explanation has been given by way of example in which there are four input terminals, it is possible to increase the number of input terminals to any desired number by providing input differential circuits, control terminals, control transistors, and negative feedback circuits corresponding to the number of input terminals. An electronically switched amplifier circuit can be obtained. In addition,
In FIG. 2, reference numeral 46 denotes a constant current circuit, which is effective in eliminating click sounds during switching by keeping the DC bias value at the output terminal constant, but is not necessarily necessary in the present invention. The amplifier circuit 14 is effective for eliminating interference between the load resistor 15 and the negative feedback resistor and for obtaining sufficient open circuit gain, but is not necessarily necessary. Although this has been explained above, it goes without saying that it can also be implemented using PNP transistors, FETs, and the like. Furthermore, since the circuit of the present invention is constructed using circuit elements that do not interfere with the integration of the circuit into a semiconductor integrated circuit, it is extremely suitable for integrating the entire circuit into a single semiconductor substrate.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conventional electronic switching amplifier circuit, and FIG. 2 is a diagram showing an electronic switching amplifier circuit according to an embodiment of the present invention. 26-29-----Input terminal, 30-33---Control terminal, 18-25---Transistor forming differential circuit, 34-37---Control circuit Transistors, 14, configuring the amplifier circuit, 46...
. . . Constant current source, 15 . . . Common load of the differential circuit, 38 to 45 . . . Resistors constituting the feedback circuit.

Claims (2)

[Claims] (1) Multiple differential circuits each having separate input terminals and commonly connected to the output circuit, with only one of the multiple differential circuits in operation and the remaining differential circuits stopped. a feedback circuit that separately provides negative feedback from the output circuit to the negative feedback side terminals of each of the plurality of differential circuits, An electronic switching amplification circuit characterized by amplifying only an input signal to an input signal with a desired gain and outputting the amplified signal. (2) The electronic switching amplifier circuit according to claim 1, wherein the control circuit comprises a number of transistors equal to the number of differential circuits each having an input terminal attached to its base.