SU1378042A1 - Stable current switching device - Google Patents

Abstract

The invention relates to a pulse technique and can be used in analog-digital converters, linear voltage generators and other devices. The purpose of the invention — an increase in the integral linearity and temperature stability of the output current — is achieved by compensating for the effect of the base currents of the transistors. In the switch of this, a fifth transistor, a reference voltage follower, and a level bias unit are added to the switch. The drawing shows transistors 1-5, diodes 6 and 7, stable-current generator 8, current-generating elements IO and 11, differential amplifier 12, reference voltage source 13, reference voltage follower 14, level bias unit 15, output tin 16, input buses 17 and 18, power buses 19 and 20, a stable current switch 21, an additional level biasing unit 22, performed on a stable current generator 23, resistors shown in the diagram. The integral linearity and temperature stability of the output current of the proposed switch is higher than that of the known, due to the compensation of the influence of the base currents of the transistors. 1 z.p, f-ly, 1 ill. (Oh (L

Description

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The invention relates to a pulsed technique and can be used in analog-digital converters, linear voltage generators and other devices.

The purpose of the invention is to increase the integral linearity and temperature stability of the output current by compensating for the effect of the base currents of the transistors.

The drawing shows a diagram of a stable current switch,

The stable current switch contains five transistors 1 ,,, 5, the first 6 and second 7 diodes, a stable current generator 8, a resistor 9, the first 10 and the second I1 current-generating elements, a differential amplifier 12, a source 13 of the reference voltage, a voltage follower 14 , block 15 level displacement, and the collector of the first transistor 1 is connected to the output

bus 16, the base of the first 1 and second 2 transistors are connected respectively to the first 17 and second 18 input buses, the emitters of the first 1 and second 2 transistors respectively through the first 6 and second 7 diodes are connected to the first output of the resistor 9, the second output of which connected to the collector of the third transistor 3, the emitter of the first transistor 1 is connected to the stable current generator 8; the collector of the second transistor 2 is connected to the first power line 19, the emitter of the third transistor 3 is connected to the base of the fourth transistor 4, current-supply element 10 and the inverting input of the differential amplifier 12, the output of which is connected to the base of the third transistor 3, and the non-inverting input through the source 13 of the reference voltage connected to the second output of the first current-supplying element 10, the second power bus 20 and one output of the second current supply element 11, the other output of which is connected to the emitter of the fourth transistor 4, the collector of the third transistor 3 is connected to the base of the fifth transistor 5, the emitter of which is connected to the collector of the fourth transistor 4, and the collector through the bias-level unit 15 is connected to the output of the voltage follower 14, the input

which is connected to the collector of the first transistor 1,

The stable current switch also contains a sixth transistor 21 and an additional level bias unit 22, the emitter of the second transistor 2 being connected through an additional level bias unit 22 to the base of the sixth transistor 21, whose collector and emitter are respectively connected to the collector and emitter of the fifth transistor 5.

An additional level bias unit 22 can be performed, for example, on a stable current generator 23, which is connected to one pin of an additional level bias unit 22 and through a resistor 24 to another terminal.

Switch stable current works as follows.

The reference voltage of source 13 is compared by a differential amplifier 12 with the voltage on the first current-setting element 10, the voltage on the current-giving element 10 maintained at the same voltage as the source 13 of the reference voltage, sets the output current of the device. The differential (paraphase) signal in ECL logic levels, fed through the first 17 and second 18 input buses to the bases of the respective first 1 and second 2 transistors, switches the differential current switch (transistors I, 2, diodes 6, 7, generator 8, resistor 9, block 22) from one conductive state to another, switching the output current of the device I to the output bus 16 or to the first power bus 19.

The stability and integral linearity of the output current is determined mainly by the current 1 of the base of the first transistor 1 and the current 1 of the base of transistor 3. To compensate for the temperature change of the base current 1 of transistor 3 to the emitter of transistor 3, the base of the second current supply element 11 is connected is set equal to the current I of the first current supply element 10,

In this way ,

Subject to the implementation of transistors 3 and 4 on the same substrate by the integrated technology and the equality of the electrical modes of operation (equality of the operating currents and the collector-base voltage). those. there is full compensation of the effect of the base current of the transistor 3,

The base current I, the first transistor 1 depends on two factors. Along with the temperature drift due to the ambient temperature, it has a temperature drift due to the variable value of the dissipated power at the junction of the first transistor 1 due to a change, the voltage on the output bus 16 of the device and the variable (random) duty cycle of the output pulses current.

There is also a dependence of the magnitude of the base current I, on the absolute magnitude of the collector-base voltage of the first transistor 1, which is the cause of the integral nonlinearity of the output current I of the device (i.e., the dependence of the output current I on the output voltage 16 of the device) . The integral nonlinearity of the output current I is an important jxa-characteristic that evaluates the quality of the functioning of the proposed device as a switch for current stability. To compensate for the current of base 1y, the base of the emitter of the first transistor 1 includes the base of transistor 5, which is in identical electrical operation. The mode currents of the transistors 1 and 5 are equal, the collector-base voltages are also kept equal during operation of the device due to the communication through the voltage follower 14 and the level bias unit 15.

Thus, it follows from I Ij +, i.e. ,, i.e. there is a full compensation of the effect of the base currents of transistors 1 and 3.

Dp ensure the identity of the thermal modes of the transistors 1 and 5 by ensuring equal power dissipation on their collector power

During the switching of the output current, a transistor 21 is introduced. At the same time, during switching of the output current I, equal currents flow through the device I and 5 and equal power is generated in their collector transitions. In the pauses between switching on the output current I transistors 1

0 5 O, 0

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and 5 are both in a de-energized state.

To switch the transistor 21, the additional level bias unit 22 must provide the dUcAB 0, ZZV + IR, offset voltage.

The integral linearity and temperature stability of the output current of the proposed stable current switch is higher than that of the known, by compensating for the effect of the base currents of the transistors.

Claims (1)

1. A stable current switch containing a transistor circuit, the first and second diodes, a stable current generator, a resistor, the first and second current supplying elements, a differential amplifier, a voltage source, the collector of the first transistor connected to the output bus, the bases of the first and second transistors are connected to the first and second input respectively, the emitters of the first and second transistors, respectively, through the first and. The second diode is connected to the first output of the resistor, the second output of which is connected to the collector of the third transistor, this is the first transistor connected to the stable current generator, the collector of the second transistor is connected to the first power bus, the emitter of the third transistor is connected to the first current supply terminal element and the inverting input of the differential amplifier, the output of which is connected to the base of the third transistor, and the non-inverting input through the source of the reference voltage It is connected to the second output of the first current supplying element, the second power supply terminal and one output of the second current supplying element, the other output of which is connected to the emitter of the fourth transistor, characterized in that, in order to increase the integral linearity and temperature stability of the output current, the fifth transistor is inserted, repeater unit and a level bias unit, moreover, the collector of the third transistor is connected to the base of the nth transistor, the emitter of which is connected to the collector of the fourth trans-53780426 the resistor, and the collector through the block the sixth transistor and the additional A level is connected to the output of a co-level offset unit, with the emitter a voltage repeater, the input of which of the second transistor is additionally connected to the collector of the first transistor displacement unit of the level of the connection capacitor. It is connected to the base of the sixth transistor, whose collector and emitter is correspondingly 2. The switch according to claim 1, 1, and 2 o and -who are connected to the collector and This is due to the fact that they were introduced to an emitter of the fifth transistor.