JPH0319413A - Current output type differential amplifier circuit - Google Patents

Abstract

PURPOSE:To make the collector voltage of a differential amplifier circuit equal to each other by incorporating a buffer amplifier to collectors of the differential amplifier circuit. CONSTITUTION:Transistors(TRs) 11, 12 forming a differential amplifier circuit, a constant current source 33, TRs 13, 14 making the collector voltage of the TRs 11, 12 equal to each other and TRs 15-19 forming a current mirror circuit are provided to the differential amplifier circuit. Since the collector voltage of the TRs 11, 12 is equal to each other, the effect of the collector current due to the difference from the collector voltage is eliminate, A buffer circuit is incorporated in the collector of the differential amplifier circuit to eliminate the effect of the amplitude of an output voltage onto the distortion.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a current output type differential amplifier circuit capable of reducing the distortion rate of output current.

Conventional technology In recent years, coils have been created as circuits in semiconductor integrated circuits,
Techniques that increase the values of capacitors and resistors using circuits have come into use. It is also being used in the audio field.

A conventional current output type differential amplifier circuit will be explained below.9 FIG. 2 shows a conventional current output type differential amplifier circuit. 51
and 52 are transistors forming a differential circuit with common emitters, and 53 is a constant current source.

Transistors 54, 55, 56, 57, and 58 constitute a non-current mirror circuit, and the difference between the collector currents of the transistor 52 and the transistor 58 is the output current. V1
and V2 are input voltages, 59 is a load resistance, and V3 is a reference voltage.

When voltages V1 and V2 are applied to the bases of transistors 51 and 52, the collector currents of transistors 51 and 52 are as follows: V^: Early voltage of transistor VCE51:
Collector-emitter voltage VCI of transistor 51! 52: Collector-emitter voltage of transistor 52 i) Zero collector current of transistor 58 I C5B is Icsa = for base current correction and early voltage correction circuit
It becomes Ics+.

Output current I. ut is I out ” I CS8 1 C'52...
...('?) becomes asymmetric and distortion occurs. This is transistor 52
This is because the collector voltage changes simultaneously with the output voltage, and the collector current changes due to the Early effect.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a current output type differential amplifier circuit that can reduce distortion caused by the amplitude of the output voltage.

Means for Solving the Problems To achieve this object, the current output type differential amplifier circuit of the present invention reduces distortion by applying amplitude changes of the output voltage equally to both transistors of the differential amplifier. I have relatives who do.

Effect: With this configuration, the collector-emitter voltages of the transistors constituting the differential circuit can be equalized, and the influence of differences in collector current due to differences in collector voltage can be eliminated.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit showing one embodiment of the present invention. In FIG. 1, 11 and 12 are transistors forming a differential circuit, and 33 is a constant current source.

13 and 14 are transistors for making the collector voltages of transistors 11 and 12 equal. 15 to 1
9 is a transistor constituting a current mirror.

Since the collector voltages of the transistors 1l and 12 are equal, equations (4) and (6) become 1, and the output current I. utl dimension, which is the ideal state.

As described above, by inserting a buffer circuit into the collector of the differential circuit, it is possible to eliminate the effects of distortion caused by the amplitude of the output voltage.

Effects of the Invention As described above, according to the present invention, by inserting a buffer amplifier into the collector of the differential circuit, it is possible to obtain the effect that the collector voltages of the differential circuit are equalized and distortion is reduced.

[Brief explanation of drawings]

11.12...Differential pair transistor, 13,1
4...Buffer amplifier transistor, 15,1
6.17.18.19... Current mirror transistor, 33... Constant current source, 59...
- Load resistance, 51.52... Differential pair transistor, 53, 54.55, 56.57... Current mirror transistor, 53... Constant current source.

Claims (1)

[Claims] It is equipped with a differential amplifier, a circuit that equalizes the voltage between the collector and emitter of the two transistors that make up the amplifier, and a circuit that changes the voltage between the collector and emitter in synchronization with the output voltage, and a current mirror circuit as a load. Current output type differential amplifier circuit.