2 CMOS LARGE CURRENT-GAIN CELLS WITH LINEARLY VARIABLE GAIN AND CONSTANT BANDWIDTH

Two CMOS current gain cells with a linear open-loop transfer characteristics are proposed; one for differential inputs and the other for single-ended input. Both cells have a large gain variable linearly via a small dc current, a constant bandwidth independent of the gain, and a very low distortion over a large input range. Different implementations are discussed and compared. Computer simulations on the single-ended cell show a gain of 0.75 to 130 with the control current from 4 to 15 muA, a THD of less than 0.5% for input up to 70% of the control current, and a constant bandwidth of 1.4 MHz.