Patent ID: 7489146

Claim:
A voltage/current (V/I) source comprising: circuitry comprising first, second, third and fourth nodes; a first current source electrically connected to the first node; a second current source electrically connected to the second node, the third and fourth nodes being between the first and second nodes; an operational amplifier (op-amp) having an output, an inverting input, and a non-inverting input, the output being electrically connected to the third node, and the non-inverting input being electrically connected to a voltage source; a feedback line between the fourth node and the inverting input; a first circuit element between the first and fourth nodes; a second circuit element between the second and fourth nodes; a third circuit element between the first and third nodes; and a fourth circuit element between the second and third nodes; wherein the first, second, third and fourth circuit elements are configurable to permit or restrict current flow.