A low voltage CMOS current source

A low voltage current source is described that has a minimum input voltage of less than 0.1 V and a minimum output voltage swing of 0.2 V. Although this current source has an output voltage range equivalent to a simple current mirror, the output resistance is amplified by a feedback amplifier to produce an output resistance on the order of a cascode current source. The low voltage current source was fabricated in a 2 micron n-well CMOS process. The measured minimum output voltage is 0.2 V and the measured output resistance is 11 M/spl Omega/. Using this current source, a 1.8 V folded-cascode op amp was designed. The simulated open loop gain was 50 dB with a nearly rail-to-rail output linear range.