JPH01209807A - Amplifier circuit - Google Patents

Abstract

PURPOSE:To eliminate the need for a constant voltage source and to obtain an output signal with a fluctuation component of power supply eliminated sufficiently therefrom by forming the amplifier circuit such that the output signal in opposite phase to that of an input signal is obtained by means of a constant current source. CONSTITUTION:The constant current source ICC comprising diodes D1, D2, D3, resistors R7, R8 and a transistor(TR) Q2 is connected to the circuit. A collector resistor R6 is connected between the collector of an amplification TR Q1 and a ground line. With an input signal given to an input terminal IN, when a current 1, of the collector of the TR Q1 changes into a current I1 +i by the input signal, a current I2 to the collector resistor R6 changes into I2-i. The output signal obtained from the output terminal OUT via a coupling capacitor C2 from the collector of the TR Q1 is outputted in the opposite phase to that of the input signal independently of the fluctuation of the power supply.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an amplifier circuit that obtains an output with the opposite phase of an input signal.

[Conventional technology]

A simple amplifier circuit that takes out a negative phase output is a common emitter circuit using a transistor stage. FIG. 2 shows an equalizer circuit using such a common emitter circuit. In the figure, a current feedback bias is applied to the amplifying transistor Q1 by a collector resistor R3, an emitter resistor R4, and voltage dividing resistors rjl and rt2 that set the base potential. The input terminal from the collector of the amplification transistor Q1! A human input signal applied to the base from N via coupling capacitor C1 and an emitter grounded output in reverse phase are taken out via coupling capacitor C2, and an in-phase emitter follower output is also output from the emitter via coupling capacitor C3. It is taken out. What is the composite ratio of the negative phase and positive phase outputs of variable resistor R5? An emphasized signal of a specific band component centered around the resonant frequency of the resonator DR, which is provided to set the gain of the entire JN adjustment amplification concave path and is connected between the sliding terminal T and the ground line, is output to the output terminal OU. Obtained at '1'.

[Problem to be solved by the invention]

In a conventional amplification circuit in which the collector of an amplification transistor is connected to a power supply +Vcc via a collector resistor, when the power supply voltage fluctuates, a fluctuation component is superimposed on the output signal. Therefore, it is necessary to separately provide a power supply stabilizing circuit to suppress fluctuations in the power supply voltage.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a constant current source between the collector of an amplifying transistor to which an input signal is applied to the base and the power supply, and connects the collector to ground via a resistor (collector resistor). A signal with the opposite phase to the input signal is extracted from the input signal.

[Effect]

According to this configuration, when there is no input signal, the current from the constant current source flows to the collector side of the amplification transistor and the collector resistance side. Then, when the input signal is input,
For example, when the current m flowing to the collector side increases, the amount of current flowing to the collector resistance side decreases. therefore,
The output terminal outputs an output signal having a phase opposite to the input signal. And the change in current in this case is unrelated to fluctuations in the power supply.・

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram of an amplifier circuit according to an embodiment of the present invention used in a graphic equalizer, and parts corresponding to those in FIG. 2 are given the same reference numerals. In FIG. 1, IN is an input terminal. Ql is an amplification transistor, R1, R2, rt4 are resistors, 01 to C3 are coupling capacitors, +VCC is a power supply,
115 is a variable resistor, and DR is a series resonator. The configurations of this embodiment that differ from the conventional example are as follows. However, the amplifier circuit of this embodiment uses diodes DI and D instead of the resistor R3 connected between the collector of the amplifying transistor Q1 and the power supply Vcc in FIG.
2. D3, a constant current source 1cc composed of resistors R7 and R8, and a transistor Q2 are connected, and a collector resistor R3 is connected between the collector of the amplifying transistor Q1 and the ground line. . The rest of the configuration is the same as that of the conventional example, so a description thereof will be omitted. Explain the operation. First, when no input signal is applied to the input terminal IN, the current from the constant current source Ice is the current I+ to the collector side of the amplification transistor Q1 and the current I to the collector resistor R6 side. It is divided into two parts. Next, when an input signal is applied to the input terminal IN, the input signal causes the amplification transistor Ql to
When the current to the collector side of ■1 changes to It+i, since the collector and the collector resistor R6 are commonly connected by the constant current source Ice, the current to the collector resistor R6 side! , becomes R5-i. This means that the phase of the output signal from the coupling capacitor C3 side is the same as that of the input signal, whereas the phase of the output signal output from the output terminal OUT connected to the coupling capacitor C2 is the same as that of the input signal. On the other hand, it is in reverse phase. Furthermore, since the internal impedance of the constant current source 1cc is larger than the load impedance of the amplifier circuit, in the amplifier circuit of this embodiment, the output signal obtained from the output terminal OUT from the collector of the amplification transistor Trt via the coupling capacitor C2 is as follows. Regardless of power supply fluctuations, the input signal will be output in the opposite phase relationship.

【effect】

As is clear from the above explanation, according to the present invention,
Since the configuration is configured such that an output signal having the opposite phase of the input signal can be obtained from the output terminal using a constant current source, there is no need to use a constant voltage source, resulting in cost reduction, and the power supply is not connected to the output terminal from the output terminal. It is possible to provide an amplifier circuit that can obtain an output signal from which fluctuation components of

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an amplifier circuit according to an embodiment of the present invention, and FIG.
The figure is a circuit diagram of an amplifier circuit according to a conventional example. IN...input terminal, Ql...amplification transistor,
R6...Resistor, Cl-C5...Coupling capacitor, O
U1゛...output terminal, Ic'c...constant current source.

Claims (1)

[Claims] (1) A constant current source is provided between the collector of the amplification transistor to which the input signal is applied to the base and the power supply, the collector is grounded via a resistor, and a signal with the opposite phase to the input signal is extracted from the collector. Amplification circuit.