Browse Prior Art Database

Multifunction Programmable Current/Voltage Source

IP.com Disclosure Number: IPCOM000061298D
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Ballou, RV: AUTHOR [+5]

Abstract

This article describes a circuit arrangement which provides a constant current or voltage with magnitudes defined under program control. In order to diagnose electrical problems in the automobile utilizing a technician terminal, it is a requirement to have a probe card which has the capability of sourcing voltages and currents under the control of the terminal. It is the requirement of the circuit arrangement disclosed herein to provide the 1) +12 volts or +5 volts with current limited to 1 ampere, 2) constant current sourced under program control of up to 100 mA. Figs. 1 and 2 show the present circuit. Fig. 1 embodies a voltage source whose output is 0 volts (turned off), +12 volts, or +5 volts depending on the logic states of the control lines "volts on" and "switch +5/BAT". "Volts on" turns the output on or off.

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Multifunction Programmable Current/Voltage Source

This article describes a circuit arrangement which provides a constant current or voltage with magnitudes defined under program control. In order to diagnose electrical problems in the automobile utilizing a technician terminal, it is a requirement to have a probe card which has the capability of sourcing voltages and currents under the control of the terminal. It is the requirement of the circuit arrangement disclosed herein to provide the 1) +12 volts or +5 volts with current limited to 1 ampere, 2) constant current sourced under program control of up to 100 mA. Figs. 1 and 2 show the present circuit. Fig. 1 embodies a voltage source whose output is 0 volts (turned off), +12 volts, or +5 volts depending on the logic states of the control lines "volts on" and "switch +5/BAT". "Volts on" turns the output on or off. "Switch +5/ BAT selects either a 5-volt or 12-volt output by causing pin 2 of U112A to be held to +5V reference or allowed to float up to the 12-volt supply. U112A and Q103 form the voltage source. Current limiting of 1 ampere is achieved with R111 as the feedback element to Q101 which in turn gates off Q102 if the limit is reached. Fig. 2 embodies a programmable constant current source circuit. Feedback is provided to U110A by R117 and (if selected) R118. Programming is done through a digital-to- analog converter at "OP AMP IN". All of the current switches are enhancement- mode MOSFET power devices whi...