SU1689926A1 - Controlled power source - Google Patents

Abstract

The invention relates to electrical engineering and can be used in secondary power sources of measuring devices. The goal is to increase the output impedance. The device contains an operational amplifier 4, a current-setting resistor 3, current reflectors 6 and 7 Connecting the inverting input of the amplifier 4 and the outputs of the reflectors through a resistor 3 to the second source 2 of the control voltage, the non-inverting input to the first source 1 of the control voltage the power pins of the amplifier 4 to the inputs of the reflectors 6 and 7, and the output to the load allows to form negative feedback on the load current and thereby significantly increase the output impedance of the device oystva 1 il.

Description

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The invention relates to electrical engineering and can be used in secondary power sources of measuring devices.

The aim of the invention is to increase the output impedance of a controlled current source.

The drawing shows a circuit diagram of the source.

The controlled current source contains the first 1 and second 2 input control voltage sources connected to the common bus, a current-setting resistor 3, an operational amplifier 4 whose output through the load 5 is connected to the common bus, the first current reflector 6 including resistors 6.1, 6.2 and bipolar transistors 6.3-6.5, pnp-type, second current reflector 7 including resistors 7.1, 7.2 and bipolar transistors 7.3-7.5 np-type, and input buses 8 and 9 for connecting a bipolar power source, the middle output of which is connected to a common bus. In the current reflector 6, the combined base terminals of the transistor 6.5 and the collector of the transistor 6.4 form the input of the current reflector, and the collector output of the transistor 6.5 forms the output of the current reflector. The common terminal of the current reflector 6 is formed by the combined leads of resistors 6.1 and 6.2 and is connected to the bus 8. In the current reflector 7, the combined terminals of the transistor 7.5 and collector of transistor 7.4 form the input of the current quencher and the collector output of the transistor 7.5 forms the output of the current reflector. The common terminal of the current reflector 7 is formed by the combined terminals of the resistors 7 1 and 7.2 and is connected to the bus 9.

In the device, the source 2 through a resistor 3 is connected to the inverting input of the amplifier 4 and the combined outputs of the current reflectors 6 and 7. Source 1 is connected to

About 00

oh oh oh

non-inverting input of amplifier 4. The inputs of current reflectors are connected to the corresponding power terminals of amplifier 4.

In the device reflectors 6 and 7 of the current can be implemented by other electrical circuits. One of the sources 1 or 2 may be missing, and its circuit must be connected to the common bus.

The controlled current source operates as follows.

If the voltages of sources 1 and 2 are equal, zero is close to zero and the input current 1 is through the current setting resistor 3, since the amplifier 4 maintains the voltage between its inputs close to zero.

l3 (UBXi-UBx2) / R3.

In the node of the inverting input amplifier fair current balance

1z + 1b + 17 0, where b the current output of the current reflector 6;

I is the output current of the current reflector 7.

The consumption currents 1П1 and In2 of amplifier 4 and output current 1Н in the load are related by

1n + .1п1 + 1п2 0.

The conversion factors Ke and K of the current reflectors 6 and 7 are related by

Kb b / 1b R & -2 / Re-i;

K7 l7 / ln2 R7-2 / R7-1.

With this in mind, the current 1H is determined by the formula

. „- (U.xi-U..Z.. / Кб-2,

MR6-fR7-2-1) If the coefficients KB and K are equal, the current in the load is proportional to the voltages of sources 1 and 2 and does not depend on the load resistance

1n (iBx1-iBx2)

 R7-1

РЗ R7-2

Claims (1)

The output impedance is determined by the properties of the amplifier 4 and the stabilizing properties of the negative feedback circuit. With unit coefficients Kb and K, the current through the load is equal to the current through the resistor 3, and the output resistance is large. In the known device, it is determined by parallel-connected differential resistances of transistors and is not high enough. Thus, in comparison with the known, the proposed current source has a higher output resistance. Claims A Controlled Current Source Containing an Operational Amplifier, the non-inverting input of which is connected to the first 0 input terminal for connecting the first grounded source of control voltage, inverting input - with the first terminal of the current-carrying resistor, power terminals - with the input terminals of the first and 5 of the second current reflectors, the common terminals of which are connected to input buses for connecting a grounded two-pole power source, an output bus for connecting a grounded load, the output terminals of current reflectors are combined, characterized in that, in order to increase the output impedance, the output of the operational amplifier is connected to the output bus, the output terminals of the current reflectors are connected to the first output of the current-conducting resistor, the second output of which is connected to the second input output for connecting the second one is grounded th source of control voltage. 2-ueu ev S-rh