SU923005A1 - Modifications of current generator - Google Patents

Description

(54) CURRENT GENERATOR (ITS OPTIONS)

one

The invention relates to automatics and measurement technology and can be used to obtain the output current of a device, independent of the output resistance.

A current generator is known that contains two operational amplifiers (OA), three resistors and a grounded load, the non-inverting input of the first op-amp connected to the common bus, and its inverting input through the first resistor is connected to the input source, the output of the first op-amp connected to the first output of the second resistor and through the third resistor - with a grounded load 1.

However, the stability of the output current in such a generator is not high.

The purpose of the invention is to increase the stability of the output current.

The goal is achieved in that a current generator contains two operational amplifiers (OA), three resistors and a grounded load, the non-inverting input of the first op-amp connected to the common bus, and its inverting input through the first resistor is connected to the input source

With the first output of the second resistor, and through the third resistor with a grounded load, between the second output of the second resistor and the inverting input of the first op-amp is connected to a controlled resistance, the control input of which is connected to the output of the second op-amp, the inputs of the second op-amp are connected to the second output of the second resistor and grounded load, respectively.

FIG. Figure 1 shows the basic electrical circuit of the generator (the first option).

This generator contains the first and second operational amplifiers (OA) 1 and 2, the first, second and third resistors 3-5, controllable resistance 6, grounded load 7 and source 8 of the input signal.

Works such a generator as follows.

Suppose that operational amplifiers 1 n 2 are ideal, and controllable resistance 6 has no control circuit consumption, i.e. current J63 is zero.

With these sentences, current Ja is equal to current -if, and current J4 therefore

U4 R4 J3, (1)

where U4 is the voltage across the second resistor 4;

R4 is the value of resistor 4. Since the voltage between the differential inputs of the second operational amplifier 2 is equal to zero, the voltage 1) 4 is equal to the voltage Uj. Out of this, we have

R4

Js - J3 (2)

where RS is the resistance of the third resistor 5 ,,

Since the current Jj is equal to the current in the grounded load 7 JT, we get.

H4

J, j,, (3)

RS

where J7 is the current in the grounded load.

Since the voltage at the summing point of the first operational amplifier 1 is zero, the current Js is determined by the following relation:

 and

(four)

J

RS

resistance of the first resistor 3;

where Rj Us is the voltage value of the input source 8. Substituting (4) and (3), we obtain

11 - Jrk. -Bi.f

.

As can be seen from (5), the current in the load J7 depends only on the resistance value of the grounded load 7.

When changing the resistance of the grounded load 7, the equality of the voltages U4 and Us is violated, the second operational amplifier 2 acts on the controlled resistance 6 in such a way as to establish the equality of these voltages. .

A current generator is known, two different operational amplifiers (op-amps), three resistors and a grounded load, the non-inverting input of the first op-amp connected to the common ishna, and its inverting input through the first resistor to the input source; 1l, and through the second resistor to its output, which is connected to the first output of the third resistor 1.

In this generator, low stability, the magnitude of the output current.

The purpose of the invention is to increase the stability of the output current.

The goal is achieved by the fact that a current generator containing two operational amplifiers (OA), three resistors and a grounded load, the non-inverting input of the first op-amp connected to the common busbar, and its turning input through the first resistor with a source of ingress signal, and through the second resistor with its output, which is connected to the first output of the third resistor, between the second output of the third resistor and the grounded load, is included the control 5 my resistance, the control input of which is connected to the output of the second op-amp, the inputs of the second op-amp Connect to the second output of the third resistor and the midpoint of the second resistor, respectively.

10 Pa of FIG. 2 shows the structural electric. Chesky generator circuit (second option).

The current generator contains the first and second operational amplifiers 1 and 2, the first and second resistors 3 and 4, the controlled resistance 5, the grounded load 6 and the source 7 of the input signal.

This generator works similarly. Field and MOS transistors, resistors controlled by a magnetic field (Gauss effect, Hall effect) mechanically controlled resistors can be used as controlled resistance 5. The polarity of the connection of the differential inputs of the second operational amplifier 2 is determined by the specific name of the selected controlled resistances.

The proposed current generator is simple, technologically advanced, has a high stability of the output current and can be varied widely in automation devices and measuring equipment to obtain an output current independent of the load resistance.

Claims (2)

1. A current generator containing two operational amplifiers (OA), three resistors and a grounded load, the non-inverting input of the first op-amp connected to the common bus and its inverting input through the first resistor to the input source, the output of the first op-amp connected to the first output the second resistor, and through the third resistor - with a grounded load, characterized in that, in order to increase stability, the magnitude of the output current between the second output of the second resistor and by the inverting input of the first op-amp connected a controlled resistance, the control input of which is connected to the output of the second op-amp, the inputs of the second op-amp connected to the second output of the second resistor and grounded load, respectively. 2. A current generator containing two operational amplifiers (op amps), three resistors and a grounded load, the non-inverted input of the first op-amp connected to the common bus, and its inverting input through the first resistor to the input source, and through the second resistor to its output, which is connected to the first output of the third resistor, characterized in that In order to increase the stability of the output current, between the second output of the third resistor and the grounded load, a controllable resistance is connected, the control input of which is connected to the output of the second op amp, the inputs of the second op amp are connected to the second in the output of the third resistor and the midpoint of the second resistor, respectively. Sources of information taken into account in the examination 1. Analog integrated circuits. Ed. J. Connelly. M., Mir, 1977, p. 344, FIG. 8.14.