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Monolithic Current Source

IP.com Disclosure Number: IPCOM000090159D
Original Publication Date: 1969-Feb-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Moore, RL: AUTHOR [+3]

Abstract

The matching of base-emitter voltage drops on monolithic chips in this circuit provides a number of pulsed current sources whose magnitudes are equal to or an integral multiple of a control current. When a negative pulse is applied to the base of Q1 it turns Q1 off thus forward-biasing the base-emitter junction of Q2. This establishes a well-defined reference voltage, Vbe of Q2, at the base of Q3.A differential amplifier consisting of R2, Q3 and Q4 in conjunction with a feedback loop consisting of R3, R4, Q4 and Q5 establishes an output voltage VO for the differential amplifier which has a low source impedance and a value equal to Vbe of Q2. The placement of the voltage VO at the bases of T1 and T4 makes the collector currents for each of those transistors equal to Ic.

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Monolithic Current Source

The matching of base-emitter voltage drops on monolithic chips in this circuit provides a number of pulsed current sources whose magnitudes are equal to or an integral multiple of a control current. When a negative pulse is applied to the base of Q1 it turns Q1 off thus forward-biasing the base-emitter junction of Q2. This establishes a well-defined reference voltage, Vbe of Q2, at the base of Q3.A differential amplifier consisting of R2, Q3 and Q4 in conjunction with a feedback loop consisting of R3, R4, Q4 and Q5 establishes an output voltage VO for the differential amplifier which has a low source impedance and a value equal to Vbe of Q2. The placement of the voltage VO at the bases of T1 and T4 makes the collector currents for each of those transistors equal to Ic. These collector currents can then be used separately as current sources or summed together to provide current sources which are multiples of the control current Ic.

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