JPH04257106A - Current-voltage converting circuit - Google Patents

Abstract

PURPOSE:To use a circuit even in a high frequency area without restrictions on band due to an operational amplifier by not using the operational amplifier to constitute the circuit. CONSTITUTION:The voltage to the ground of an input terminal 1 of a bias circuit 6 is 0V, and the bias circuit 6 gives the bias voltage which flows an idle current to transistors TRs 4 and 5. When a current flows from the input terminal 1, the collector current of the TR 5 is increased or reduced in proportion to increase or reduction of the input current, and the collector current of the TR 4 is reduced or increased contrarily. The voltage drop of load resistors 2 and 3 is changed by the change of respective collector currents. This voltage change is outputted to an output terminal 11 through two emitter follower circuits consisting of TRs 7 and 9 and level shift circuits 9 and 10.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current-voltage conversion circuit, and more particularly to a current-voltage conversion circuit that requires high speed performance.

0002

2. Description of the Related Art As shown in FIG. 2, a conventional current-voltage conversion circuit includes an operational amplifier 21 whose negative side input is connected to an input terminal 23 and whose output is connected to an output terminal 24;
A feedback resistor 22 connected between the output of 1 and the negative input.
It has

In this circuit, when the amplification degree of the operational amplifier 21 is extremely large, the output voltage V0 is as follows: V0=-i·Rf where i=the input current value given to the input terminal 23. Rf
=Resistance value of feedback resistor 22.

Since it can be expressed as follows, it operates as a current-voltage conversion circuit.

[0005]

[Problems to be Solved by the Invention] This conventional current-to-voltage conversion circuit assumes that the amplification degree of the operational amplifier used is extremely large. It has been difficult to realize a current-voltage conversion circuit.

[0006]

[Means for Solving the Problems] The current-voltage conversion circuit of the present invention is a current-voltage conversion circuit that converts an input current value into a voltage and outputs the voltage, and has an emitter terminal connected to an input terminal and a base terminal connected to the voltage. a first NPN transistor connected to a bias circuit and having its collector terminal connected to a positive power supply via a first load resistor; an NPN type first transistor having an emitter terminal connected to the input terminal and a base terminal connected to the bias circuit; a PNP type second transistor connected to a negative power supply via a second load resistor, and a voltage drop proportional to the current value applied to the input terminal is applied to the first and second load resistors. This is a configuration that generates

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. In the bias circuit 6, the voltage between the input terminal 1 and the ground is 0V.
and the positive power supply (VCC) through load resistor 2.
A bias voltage is applied to the bases of the transistors 4 and 5 so that an idle current flows through the NPN transistor 4 connected to the load resistor 4 and the PNP transistor 5 connected to the negative power supply (VEE) through the load resistor 4. Give it to the terminal.

When a current flows into this circuit from the input terminal 1, the sum of the inflow current, the emitter current of the transistor 4, and the collector current of the transistor 5 becomes 0.
The collector current of transistor 4 decreases in proportion to the input current, and the collector current of transistor 5 increases.

On the other hand, when a current flows out from the input terminal 1 of this circuit, the collector current of the transistor 4 increases and the collector current of the transistor 5 decreases in proportion to the current value.

As the collector currents of the transistors 4 and 5 change, the voltage drops across the respective load resistors 2 and 3 also change. By outputting these voltage changes to the output terminal 11 through an emitter follower circuit composed of a transistor 7 and a level shift circuit 9, and an emitter follower circuit composed of a transistor 8 and a level shift circuit 9, a current is generated. A voltage conversion is performed.

0012

As described above, the present invention has the advantage that a current-voltage conversion circuit can be realized without being limited by the band of an operational amplifier, and can be used even in a high frequency region.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a block diagram of an example of a conventional current-voltage conversion circuit.

[Explanation of symbols]

1 Input terminal 2, 3 Load resistor 4, 5, 7, 8 Transistor 6 Bias circuit 9,10 Level shift circuit 11 Output terminal

Claims (1)

[Claims] 1. A current-voltage conversion circuit that converts an input current value into a voltage and outputs the voltage, the emitter terminal being connected to the input terminal, the base terminal being connected to a bias circuit, and the collector terminal being connected to a first load resistor. N connected to the positive power supply through the
a first transistor of PN type; and a second transistor of PNP type, having an emitter terminal connected to the input terminal, a base terminal connected to a bias circuit, and a collector terminal connected to a negative power supply via a second load resistor. A current-voltage conversion circuit comprising: generating a voltage drop in the first and second load resistors in proportion to a current value applied to the input terminal.