SU1698801A1 - Current stabilizer - Google Patents

Description

one

(21) 4696486/21

(22) 24.05.89

(46) 12/15/91. Bul №46

(71) Design bureau of measuring equipment Irtysh

(72) A.P. Gaskov (53) 621.374 (088.8)

(56) USSR Author's Certificate No. 1010568.cl. G 01 R 19/00, 1981.

Titze U., Schenk K. Semiconductor circuit design. M .: Mir, 1982, p. 174, fig. 12. (54) FORMAT OF STABLE CURRENT

(57) The invention relates to electronics and can be used in programmable current sources for measuring

parameters of semiconductor devices. The purpose of the invention is to expand the scope of application by expanding the range of set values of currents. In the region of small currents, the minimum value of the current in the load 6 is determined by the leakage current of field-effect transistors 2, 3, in the region of high currents, the value of the permissible currents of transistor 4. At large values of the resistances of the resistors 8, the operational amplifier 1 does not go into the limiting mode, which is prevented field-effect transistor 3. Therefore, the operating current in the load 6 is quickly established when the corresponding input voltage arrives. 1 il.

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about

The invention relates to electronics, in particular to the field of electrical measuring equipment, and can be used in programmable Current sources for measuring the parameters of semiconductor devices.

The purpose of the invention is to expand the scope of application by expanding the range of set values of currents.

The drawing shows a schematic diagram of the proposed stable current driver.

Stable current driver contains operational amplifier 1, field-effect transistors 2 and 3, transistor 4, shunt resistor 5, load b, power supply bus 7, resistor groups 8 and 9, switch 10, common bus 11, resistor 12.

The non-inverting input of the operational amplifier 1 is connected to the input terminal of the driver, the inverting input is connected to the source of the field-effect transistor 3. through the resistor 12 to the common bus 11 and through the resistors 8 to the fixed contacts of the switch 10, the output is connected to the gate of the field-effect transistors 2 and 3, the drain field-effect transistor 3 is connected to the emitter of transistor 4 through resistors 9 with fixed contacts of switch 10 and through a shunt resistor 5 to the base of transistor 4 and the source of field-effect transistor 2, the drain of which is connected through the load b nen power to bus 7, the collector of transistor 4 is connected to the drain of the FET 2, the movable contact commutator 10 is connected to the common bus.

Shaper stable current works as follows.

When receiving small output currents, one of the resistors 8 is connected to the common bus 11, the inverting input of the operational amplifier 1 is supplied with a control input voltage since the operational amplifier 1 is covered by feedback that is closed through field-effect transistors 2 and 3. At the same time, the source voltage The transistor 3 is also equal to the input, and the current in the load will be inversely proportional to the resistance of the parallel-connected resistors 12 and one of the corpses of the resistors 8. Since this current does not branch off anywhere (with the exception of small current through the gates of field-effect transistors 2 and 3), the same current will be the output current of the driver flowing through the load 6. For transistor 4, the reverse collector current can reach a large value, but the minimum output current is determined by the residual current of the field-effect transistor 3.

When receiving large-output currents, one of the group of resistors 9 is connected to the common bus. Taking into account the voltage drop across the shunt resistor 5, the field-effect transistor 2 is open, as well as the field-effect transistor 3. The feedback voltage from the emitter of transistor 4 passes to the inverting input of the operational amplifier 1. The current in the load 6 will be determined by the resistance of the parallel-connected resistors 12 and one of the group of resistors 9. The maximum output current of the driver is determined by the maximum allowable current of transistor 4.

When connecting one of the group of resistors 9, the input voltage becomes less than the voltage on the resistor 9 due to the residual current of the transistor 4, then at the output of the operational amplifier 1 the voltage goes into the negative region, but since it locks the field-effect transistor 3. This reduces the voltage across the resistor 12 to the value of the input voltage, which prevents the operational amplifier 1 from going into the limiting mode. With an increase in the input signal, the current is quickly established in the load 6.

Claims (1)

Invention Stable current driver containing an operational amplifier, the non-inverting input of which is connected to the input terminal of the driver, the inverting input is connected via a common bus resistor, the output is connected to the gate of the first field-effect transistor, the drain of which is connected to the collector of the transistor and through the load is connected to the power bus, . the source is connected to the base of the transistor and through a shunt resistor with its emitter, characterized in that, in order to expand the scope of application due to the expansion of the range of set values of currents, increase speed and reliability, it introduces a second field-effect transistor, switch, first and second groups of resistors , the first terminals of the resistors of the first group of resistors are connected to the inverting input of the operational amplifier and the source of the second field-effect transistor, the gate of which is connected to the gate of the first field-effect transistor a, the drain is connected to the emitter of the transistor and the first terminals of the resistors of the second group of resistors, the second terminals of the resistors of the first and second groups of resistors are connected to the corresponding fixed contacts of the switch, the movable contact of which is connected to the common bus.