Transistor used as an adjustable bipolar low-level DC source

The use of a saturated transistor with a collector current opposite to the usual leads to a versatile, stable, and easily adjustable dc source with an EMF ranging from -10 to +10 mV and a low temperature drift. This source may be used to compensate the input offset voltage of a monolithic opamp whenever the impedance must be kept near zero or as low as 1 /spl Omega/. It can be built into an IC design with only a single-pin control line.