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Programmable Hybrid Current Source Module

IP.com Disclosure Number: IPCOM000050069D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Blaisdell, C: AUTHOR [+2]

Abstract

This article describes a programmable current source basically comprising an amplifier 10 having an output connected to the base of a pnp Darlington transistor 11 whose collector is coupled to an output 12 whose output current is to be controlled. The emitter of the transistor 11 is coupled through a resistor R2 to a voltage source Vs and through a feedback loop 13 back to an input of the amplifier 10. The voltage source Vs is also coupled through a resistor R1 to the other input of the amplifier 10 and to the collectors of a Darlington pair of transistors 14 whose input base is coupled to Vin which provides the signal for driving the amplifier 10. The input voltage Vin is equal to [Vs - Ic R1. The precession current Ic is established with a circuit similar to the output circuit shown.

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Programmable Hybrid Current Source Module

This article describes a programmable current source basically comprising an amplifier 10 having an output connected to the base of a pnp Darlington transistor 11 whose collector is coupled to an output 12 whose output current is to be controlled. The emitter of the transistor 11 is coupled through a resistor R2 to a voltage source Vs and through a feedback loop 13 back to an input of the amplifier 10. The voltage source Vs is also coupled through a resistor R1 to the other input of the amplifier 10 and to the collectors of a Darlington pair of transistors 14 whose input base is coupled to Vin which provides the signal for driving the amplifier
10. The input voltage Vin is equal to [Vs - Ic R1. The precession current Ic is established with a circuit similar to the output circuit shown. The output current is given as Iout equals R1 Vin divided

by R3 R2.

In operation, the output current Iout is independent of the voltage at the source Vs. Thus, this circuit basically is a voltage controlled circuit which establishes a current in the resistor R1 so as to set the input voltage in the amplifier 10 to control the output transistor 11 to set and establish the voltage at the emitter of the transistor 11. Once the voltage at the emitter of the transistor 11 is established and controlled, the output current I at the collector of transistor 11 becomes independent of the voltage at the voltage source Vs. This circuit can also be modi...