JPH03214909A - Differential amplifier circuit having capacitive coupling circuit - Google Patents

Abstract

PURPOSE:To realize a differential amplifier circuit having a capacitive coupling suitable for power saving and space saving without need of a DC current source to each of the capacitive coupling circuit and the differential amplifier circuit by using the DC current source in common for the capacitive coupling circuit and the differential amplifier circuit. CONSTITUTION:A signal from a signal source 1 is inputted to a base of a 1st transistor(TR) 3, from the emitter of which an output is obtained. The output signal is given to a base of a 2nd TR 4 via a capacitor 5. The signal is amplified by a differential amplifier circuitcomprising the 2nd TR 4 and a 3rd TR 9 and an output is obtained from an output terminal 14. In this case, the capacitive coupling circuit and the differential amplifier circuit use a DC current source 8 in common and no individual DC current source is required for each of the capacitive coupling circuit and the differential amplifier circuit. Then the amplified output signal is obtained and the differential amplifier circuit having the capacitive coupling circuit suitable for saving space and power of the circuit is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a differential amplifier circuit having a capacitive coupling circuit. Conventional technology Below, a differential amplifier circuit having a conventional capacitive coupling circuit is used as a second differential amplifier circuit.
The explanation will be based on the circuit diagram shown in the figure. A conventional differential amplifier circuit having a capacitive coupling circuit includes a signal source 17, a first DC voltage source 18 that biases the signal source 17, and a signal source 1 at the base.
The signal from 7 is input, and the collector is the power supply terminal (VCC)
33 and a second transistor 19 whose collector is connected to the emitter of the first transistor 19.
a first direct current source 24 connected between the emitter of the second transistor 20 and the ground terminal (GND) 34, and a transistor 20 connected between the emitter of the first transistor 19 and the collector of the second transistor 20. A capacitor 21 connected between the common connection point and the base of the second transistor 2G, and a second direct current connected to the common connection point between the capacitance 21 and the base of the second transistor 20 via a resistor 22. a voltage source 23; a third transistor 25 whose base is connected to a common connection point between the emitter of the second transistor 20 and the first DC current source 24;
a fourth transistor 2 which together constitutes a differential amplifier circuit;
6, the emitter of the third transistor 25 and the ground terminal 3
4, a third DC current source 29 connected between the emitter of the fourth transistor 26 and the ground terminal 34; a resistor 27 connected to a common connection point between the emitter and the second direct current source 28 and a fourth resistor 27 connected to the common connection point between the emitter of the fourth transistor 26 and the third direct current source 29; a third DC voltage source 30 biasing the base of the transistor 26;
A resistor 31 connected between the collector of 5 and the power supply terminal 33
It is configured to receive the signal from the differential amplifier circuit as an output signal at the output terminal 32. The operation of the above-mentioned conventional differential amplifier circuit having a capacitive coupling circuit will be explained below. A signal from the signal source 17 is input to the base of the first transistor 19 and output from the emitter. This output signal is inputted to the base of the second transistor 20 via the capacitor 21, outputted from the emitter of the second transistor 20, and transmitted to the third transistor 25 and the fourth transistor 2.
6 and is amplified by a differential amplifier circuit configured with an ellipse, and outputted from an output terminal 32. As mentioned above, the conventional circuit configuration requires DC current sources 24 and 28, 29 for each of the capacitive coupling circuit and the differential amplifier circuit. Problems to be Solved by the Invention As described above, in the conventional differential amplifier circuit having a capacitive coupling circuit, DC current sources 24, 28. 29 is required, saving circuit power and
It was not suitable for saving space. The present invention solves the above conventional problems, and has a capacitive coupling circuit that does not require a DC current source in each of the capacitive coupling circuit and the differential amplifier circuit, and is suitable for saving power and space in the circuit. The purpose is to provide a differential amplifier circuit. Means for Solving the Problem In order to achieve this problem, a differential amplifier circuit having a capacitive coupling circuit according to the present invention includes a first transistor whose base is connected to a signal source, and an emitter connected to the collector of the first transistor. a second transistor connected to the second transistor, a capacitor connected between the emitter of the first transistor and the base of the second transistor, and a third transistor that forms a differential amplifier circuit together with the second transistor. transistor and
It consists of a DC current source connected to a common connection point between the emitter of the first transistor and the capacitor, and the capacitive coupling circuit and the differential amplifier circuit share a DC t current source. Effect With the above configuration, a signal from the signal source is input to the base of the first transistor and output from the emitter, this output signal is input to the base of the second transistor via the capacitor, and further this signal is input to the base of the second transistor. is amplified by a differential amplifier circuit consisting of a transistor and a third transistor, and is output. Furthermore, due to the structure of the present invention, a DC current source is not required for each of the capacitive coupling circuit and the differential amplifier circuit, so a differential amplifier circuit with a capacitive coupling circuit suitable for saving labor and space in the circuit is realized. can. EXAMPLE Hereinafter, an example of the present invention will be explained based on the drawings. FIG. 1 is a circuit diagram of a differential amplifier circuit having a capacitive coupling circuit showing one embodiment of the invention. A differential amplifier circuit having a capacitive coupling circuit according to the present invention includes a signal source 1, a first DC voltage source 2 that biases the signal source 1, and a first transistor 3 whose base receives a signal from the signal source 1. and a second transistor 4 whose collector is connected to the power supply terminal 15 via the resistor 13 and whose emitter is connected to the collector of the first transistor 3, and between the emitter of the first transistor 3 and the ground terminal 16. and a capacitor 5 connected between the common connection point between the emitter of the first transistor 3 and the first DC current source 8 and the base of the second transistor 4. and a second transistor connected via a resistor 6 to a common connection point between the capacitor 5 and the base of the second transistor 4.
a third transistor 9 that constitutes a differential amplifier circuit together with the second transistor 4; a direct current source 11 connected between the emitter of the third transistor 9 and the ground terminal 16; One side is connected to the common connection point between the emitter of the second transistor 4 and the collector of the first transistor 3, and the other side is connected to the common connection point between the emitter of the third transistor 9 and the second DC current source 11. It consists of a connected resistor 10 and a third DC voltage source 12 that biases the base of the third transistor 9, and is configured to receive an output signal from the differential amplifier circuit at an output terminal 14.
The operation of the differential amplifier circuit having the capacitive coupling circuit configured as described above will be explained. A signal from the signal source 1 is input to the base of the first transistor 3 and output from the emitter. This output signal is input to the base of the second transistor 4 via the capacitor 5. This signal is amplified by a differential amplifier circuit composed of a second transistor 4 and a third transistor 9, and is output from an output terminal 14. At this time, the capacitive coupling circuit and the differential amplifier circuit share one DC current source 8, and there is no need for a DC current source for each of the capacitive coupling circuit and the differential amplifier circuit. Therefore, it is possible to obtain an amplified output signal and to realize a differential amplifier circuit having a capacitive coupling circuit suitable for saving power and space in the circuit. Effects of the Invention As described above, according to the present invention, it is possible to obtain a signal obtained by amplifying the signal from the signal source, and furthermore, since a DC current source is not required for each of the capacitive coupling circuit and the differential amplifier circuit, the circuit efficiency is reduced. A differential amplifier circuit with a capacitive coupling circuit suitable for labor and space saving can be realized.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a differential amplifier circuit having a capacitive coupling circuit according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional differential amplifier circuit having a capacitive coupling circuit. 1... Signal source, 2.7.12... DC voltage source, 3,
4, 9... Transistor, 8, 11... DC current source, 5... Capacity, 6.1G, 13... Resistor, 14... Output terminal, 15... Power supply terminal, 16. ...Ground terminal.

Claims (1)

[Claims] 1. a first transistor whose base is connected to a signal source; a second transistor whose emitter is connected to the collector of the first transistor; the emitter of the first transistor and the base of the second transistor; a third transistor that constitutes a differential amplifier circuit together with the second transistor; and a DC current source connected to a common connection point between the emitter of the first transistor and the capacitor. A differential amplifier circuit having a capacitive coupling circuit, characterized in that the capacitive coupling circuit and the differential amplifier circuit share a DC current source.