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Multiple Current Source with Compliance Voltage Detection

IP.com Disclosure Number: IPCOM000076209D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Hendershot, LE: AUTHOR

Abstract

This circuit provides a programmable choice of 4 current sources with separate compliance voltage on each range. This circuit uses only one compliance detector and the load is automatically protected against overvoltage.

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Multiple Current Source with Compliance Voltage Detection

This circuit provides a programmable choice of 4 current sources with separate compliance voltage on each range. This circuit uses only one compliance detector and the load is automatically protected against overvoltage.

The operational amplifier has a virtual ground at the negative terminal. A current is generated across P1, R1 from Vref. Since input current on the operational amplifier 3 is extremely small (nanoamps), the generated current is directed through R5 (compliance resistor) to the external load through crossover switch 1. The current returns from the external load through the crossover switch to the output of the operational amplifier. Compliance resistor R5 drops sufficient voltage to ensure that the amplifier is at saturation when the load reaches its compliance. Resistors R9 and R10 shift the saturation voltage to the linear range of detector 2. The detector compares V' to the fixed reference and furnishes an output overvoltage signal when the amplifier is saturated. The output is transformer coupled to shift from isolated current-source ground to system ground reference. The current amplitude is switched by relays 1, 2 and 3, not shown. The points of these relays designated R1-1, R1-2, etc., parallel resistors and potentiometers to R1 and R5 to change both current and compliance limits. Potentiometers P1, P2 and P3 and P4 are used to adjust the output current in each range to the precise va...