JPH0463004A - Amplifier circuit - Google Patents

Abstract

PURPOSE:To obtain an amplifier circuit with driving capacity on which the driving capacity of an individual amplifier is added by connecting the input of the amplifier circuit comprised of plural operational amplifiers to which the same feedback is applied mutually, connecting the output mutually via resistors, and taking out an output terminal from the intermediate point of those resistors. CONSTITUTION:The operational amplifiers OP1, OP2 to which full feedback is applied comprise a voltage-follower. The input are connected mutually, and are connected to an input terminal IN1. The output are connected to the output terminal VO1 via the resistors R1, R2. Since the operational amplifiers OP1, OP2 are provided with input offset voltages actually, potential difference equivalent to the difference of the input offset voltages is generated as the output of the operational amplifiers OP1, OP2. The output resistance of the operational amplifiers OP1, OP2 are low in an ordinary state, and also the full feedback is applied to them, therefore, the output resistance goes down further by the function of the feedback. By inserting the resistors R1, R2 to an output circuit, only a current DELTAVI0/(R1+R2) flows between the operational amplifiers OP1 and OP2 for the input offset voltage difference DELTAVI0 of the operational amplifiers OP1, OP2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an amplifier circuit, and more particularly to an amplifier circuit composed of an operational amplifier.

2. Description of the Related Art Conventionally, an operational amplifier has been used alone with feedback as shown in the example shown in Figure 3, and an output current corresponding to its driving capacity can be obtained. measures such as adding an output buffer were taken.

Problems to be Solved by the Invention However, in such a case, if the output buffer operates in B drive operation, crossover distortion will occur, and if in AB8 drive operation, a large amount of power consumption will occur in the bias circuit. There was a drawback.

The present invention has been made in view of the above-mentioned conventional situation,
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a novel amplifier circuit which makes it possible to eliminate the above-mentioned disadvantages inherent in the conventional technology.

Means for Solving the Problems In order to achieve the above object, an amplifier circuit according to the present invention is an amplifier circuit composed of a plurality of operational amplifiers that are given the same feedback, and whose inputs are connected to each other. , the outputs are connected to each other via resistors, and the output terminal is taken out from the midpoint between those resistors.

EXAMPLES Next, preferred embodiments of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of an amplifier circuit according to the present invention.

In FIG. 1, operational amplifiers OPI and O20 are both provided with full feedback and constitute a portige lower. The inputs are interconnected and connected to an input terminal INI. The output is sent to the output terminal VO via resistors R1 and R2.
Connected to I. Since operational amplifiers OPI and O20 actually have input offset voltages, the outputs of operational amplifiers OPI and O20 produce a potential difference corresponding to the difference in input offset voltages. Operational amplifier OPI and O20
Normally, the output resistance is low, and since full feedback is provided, the output resistance further decreases due to the feedback action. - As a typical example, if the output resistance of operational amplifiers OP1 and O20 is 100Ω and the gain is 1,000, then the output resistance due to feedback is 100Ω/1,000 = 0.
It becomes 1Ω.

If the difference in input offset voltage is 10mV, by directly connecting the output without resistors R1 and R2, it will be 10mV1.
0.1Ω = 100mA current flows through operational amplifiers OPI and O
Trying to flow between 20 and 20. Actually operational amplifier OPI
Although the current is limited by the driving ability of O20 and O20, a large amount of wasted current flows. By inserting resistors R1 and R2 in the output circuit, operational amplifiers OPI and O20
For the input offset voltage difference ΔVIO, Δ■+o/
Only a current of (R1+R2) flows across operational amplifiers OPI and O20. Input offset voltage difference ΔV+o=
10mJ If R1+R2=200Ω, 10m
V/200Ω-0.5mA. The drop in driving ability due to the addition of a resistor is small.

FIG. 2 is a circuit configuration diagram showing a second embodiment of the present invention.

Referring to FIG. 2, in this second embodiment, operational amplifiers OP3 and OF2 are provided with feedback using resistors.
It constitutes an inverting or non-inverting amplifier.

As described in detail, according to the amplifier circuit of the present invention, it is possible to obtain an amplifier circuit having a driving capability that is the sum of the driving capabilities of individual amplifiers.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention;
FIG. 2 is a circuit configuration diagram showing a second embodiment according to the present invention;
3 and 4 are circuit diagrams according to the prior art. OPI~opo are operational amplifiers, R1-R8 are resistors, IN
1 to ■N5 are input terminals, ■01 to v04 are output terminals, T
rlTr2 is a transistor

Claims (1)

[Claims] An amplifier circuit consisting of multiple operational amplifiers with the same feedback, whose inputs are connected to each other, whose outputs are connected to each other via resistors, and whose output terminal is taken out from the connection point of these resistors. An amplifier circuit characterized by: