| 摘要 |
An input to a rail-to-rail, FET, operational amplifier having a transconductance that is constant throughout the operating range of the operational amplifier is presented. The input of an operational amplifier typically includes an input stage, a current source and a current transfer circuit, wherein the input stage comprises both N-type transistors and P-type transistors. The present application discloses the use of a duplicate of those elements: a proportional input stage, a proportional current source, and a proportional current transfer circuit, which together are used to emulate the operation of the input stage. By monitoring these proportional duplicates, one can determine when both input pairs are operating. When both input pairs are operating, a minimum selector circuit interfaces with the current transfer circuit to reduce the current supplying one of the input pair transistors, thus reducing the overall transconductance of the circuit.
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