US Patent 7551021 Low-leakage current sources and active circuits

A low-leakage circuit includes first, second, and third transistors, which may be P-channel or N-channel FETs. The first transistor provides an output current when enabled and presents low leakage current when disabled. The second transistor enables or disables the first transistor. The third transistor connects or isolates the first transistor to/from a predetermined voltage (e.g., VDD or VSS). The circuit may further include a pass transistor that provides a reference voltage to the source of the first transistor when the first transistor is disabled. In an ON state, the first transistor provides the output current, and the second and third transistors do not impact performance. In an OFF state, the second and third transistors are used to provide appropriate voltages to the first transistor to place it in a low-leakage state. The first, second, and third transistors may be used for a low-leakage current source within a current mirror, an amplifier stage, and so on.