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# Programmable V/I Source

IP.com Disclosure Number: IPCOM000052345D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 45K

IBM

## Related People

Murty, K: AUTHOR [+2]

## Abstract

Voltage or current (V/I) stimulus using digital information is generate for use in integrated circuit testing using the same analog module.

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Programmable V/I Source

Voltage or current (V/I) stimulus using digital information is generate for use in integrated circuit testing using the same analog module.

Fig. 1 shows the schematic of the V/I source. In the voltage mode, S(1) is on and S(2) is off. The output voltage is given by: V(L)=V(1).

Op Amp A(1) sums the input and load voltages and divides the sum by 2 to yield V(1) at its output. With S(2) off, the 0p Amp A acts as a buffer. Resistor R(1) limits the current drawn by the load. In the current mode, S(1) is off and S(2) is on. In this case, the output of Op Amp A(1), is given by: V(A)=V(1)+V(L).

Because S(2) is on, the output of A(2) equals V(L)+V(1). The current I(L) i given by: I(L) = V(1) / R(I).

The magnitude of load current and the mode can be externally controlled using digital signals.

Fig. 2 shows an alternative method employing fewer Op-Amps. In the voltage mode, S(1) is on and S(2) is off. A is used as a buffer between input and load. In the current mode, the input voltage V(1) equals the voltage drop across R(1). The expression for current is the same as shown for the circuit in Fig. 1.

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