An improved CMOS current mirror using a bulk-effect independent cascode biasing structure

To reduce the channel length modulation effect, a cascode structure is very often used in current mirrors. However, this technique requires a correct biasing of the cascode transistor. The author presents a biasing structure which always guarantees the correct biasing under any process variations (parameter variations from chip to chip) or any bulk effect and ensures that all the transistors are always biased just in saturation. As a result a current mirror is realized which has a maximum voltage output swing and a very high current mirror accuracy