SU1476445A1 - Current source for switching load current - Google Patents

Abstract

The invention relates to electrical engineering and can be used in secondary sources of electrical power for electronic equipment. The purpose of the invention is to improve the stability of the load current of the current switch when changing the current transfer coefficient of the transistor. The device contains a regulating node on the first 1 and second 2 transistors and the first bias resistor 3, the current setting resistor 4, the voltage source on the third 5 and fourth 6 transistors, the diode-enabled transistor 7, the second current supply resistor 8, the second 9, the third 10 and fourth bias resistors. In the collector circuit of the transistor 1 is switched on load - switch 12 current. The resistance value of the resistor 11 is selected so that an increase in the output current of the device ensures that the current in the current switch 12 is constant. 2 Il.

Description

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The invention relates to electrical engineering and can be used in secondary power supplies of electronic equipment, in particular integrated circuits at current switches.

The aim of the invention is to improve the stability of the load current with a change in the current transfer ratio of the transistor.

FIG. 1 shows the basic electrical circuit of the proposed current source; in fig. 2 is a graph showing the dependence of the load current of the switches on the current transfer ratio of the transistor.

The current source contains a regulating node, made on the first 1 and second 2 transistors and the first bias resistor 3, the first current-setting resistor 4, the voltage source, made on the third 5 and fourth 6 transistors, the diode-enabled transistor 7, the second current one the resistor 8, the second 9, the third 10 and the fourth 11 bias resistors, the transistor 7 being connected to the output bus by a collector for connecting the load current transistor switch 12, by the emitter through the resistor 4 to the common bus and to the first terminals of the resistor ditch 3, 9 and 10 offset, and the base to the second output of resistor 3 and to the emitter of transistor 2, the collector of which is connected to the power bus and to the first output of resistor 8, the second output of which is connected to the base of transistor 2, collectors of transistors 5, 6 and 7 and the base of the transistor 7, the emitter of which is connected to the second output of the resistor 9 and through the resistor 11 to the base of the transistor 6, the emitter of which is connected to the second output of the resistor 10 and to the base of the transistor 5, the emitter of which is connected to the common bus. In the collector circuit of transistor 1 included load switch 12.

The device works as follows.

The identity of transistors 2 and 7 ensures the same voltage drop across them when the same currents flow, which is provided by resistors 9, which set a bias current that changes the base currents of transistors 1, 5 and 6 due to a decrease in their transmission coefficients

cannot significantly break the uniformity of the voltage drops at the emitter junctions of transistors 2 and 7. Transistor 5 ensures stable

current through the resistor 10. The change in voltage across the resistor 10 leads to such a change in the collector current of the transistor 5, which causes the voltage across the resistor 10 to its initial position. Transistors 1 and 6

are identical, and the resistors 4 and 10 are the same.

With large current transfer coefficients of the base transistors (B 20)

5, the base current of the transistor 6 is small, and the voltage drop across resistor 11 is less than the temperature potential. As a result, the current through resistor 10 is equal to the current through resistor 4 and is approximately equal to the output current. Approximately the same current will flow through the load Rn current switch 12.

When reducing the current transfer ratio of the base transistors drop

5, the voltage across the resistor 11 increases and the base potential of transistor 2 increases accordingly. The base potential of transistor 1 also increases. The current through the resistor 4 increases, providing an increase in the output current of the source. The resistance value of the resistor 11 is selected so that an increase in the output current of the stabilizer ensures that the current in the load is constant - the current switch 12.

Thus, the stability of the current in the load RH current switch of the proposed source (curve 13

0 in FIG. 2) significantly higher than in the prototype (curve 14 in Fig. 2).

Claims (1)

Formula of inventions Current source for a load current switch containing a regulating node made on two transistors and a first bias resistor, a first current supplying resistor, a voltage source made in a third transistor, a diode, a second current supplying resistor and the second and third bias resistors, the first transistor connected a collector to the output bus to connect a transistor switch of the load current, an emitter through the first current-setting resistor to the common bus and to the first terminals of the bias reactors, base to the second output of the first bias resistor and to the emitter of the second transistor, the collector of which is connected to the power bus and to the first output of the second current resistor, the second output of which is connected to the base of the second transistor, with the collector of the third transistor, different the fact that, in order to increase the stability of the load current when changing current transistor, the fourth transistor and the fourth bias resistor are inserted, the base of the fourth transistor is connected to the second terminals of the diode and the second bias resistor through the fourth resistor, the collector to the first diode terminal, and the emitter to the second output of the third bias resistor and with the base of the third transistor, the emitter of which is connected to the common bus.