Highly symmetrical bi-direction current sources
 A bi-directional current source which maintains accurate, substantially equal source and sink currents over a large range of output voltages. The current source includes a primary field effect transistor (FET) and two mirroring FET's. It additionally includes at least one operational amplifier for voltage balancing. An optional operational amplifier provides and additional bias voltage and transistor matching optionally provides impedance matching of the supply voltages. 
International Business Machines Corporation
H G
H03L G05F
inventional inventional
Phillipe Patrick
Girard Mone