Single Transistor High-Impedance Tail Current Source With Extended Common-Mode Input Range and Reduced Supply Requirements

A compact implementation of a single transistor tail current source with very high output impedance (>40 MOmega) and low-voltage requirements is introduced. The tail transistor can operate with less than a drain-source saturation voltage and allows implementation of low-voltage differential pairs with wide common-mode input range and very high common-mode rejection ratio. Simulation and experimental results are shown that validate the proposed circuit.