Leakage current compensation circuit

Claim 1

In an electrical circuit including a workpiece bipolar transistor having first and second electrodes with a reverse-biased semiconductor pn junction therebetween, which workpiece pn junction tends to exhibit a leakage current, leakage current compensating means for diverting said leakage currents to itself and from other portions of said electrical circuit, which leakage current compensating means comprises: an auxiliary semiconductor pn junction having a similar profile to said workpiece pn junction, having first and second electrodes and being located to be subject to similar thermal conditions as said workpiece pn junction; potential bias means for establishing a reverse bias potential across said auxiliary junction having a quiescent value substantially the same as that of the reverse bias operating potential across said workpiece pn junction, responsive to which an auxiliary leakage current will tend to flow through said auxillary junction; and first current mirror means having an input terminal which connects to the first electrode of said auxiliary pn junction for receiving the leakage current flowing through the first electrode of said auxiliary semiconductor pn junction and having at least a first output terminal which connects to the first electrode of said workpiece bipolar transistor, said current mirror means responsive to the auxiliary leakage current flowing through its input terminal to conduct via its output terminal leakage current flowing through the first electrode of said workpiece bipolar transistor to avoid its being conducted by said other portions of said electrical circuit.