MOS CURRENT GAIN CELLS WITH ELECTRONICALLY VARIABLE GAIN AND CONSTANT BANDWIDTH

Two MOS current gain cells that provide linear amplification of currents supplied by several linear MOS V-I converters are proposed. One has a voltage-controlled gain and the other a current-controlled gain. It is shown how linear current gain is obtained in these circuits, using the square-law MOS characteristic. The MOS gain cells have a constant (gain-independent) bandwidth. This is because the transconductance of a MOS transistor can be varied without affecting its gate-source capacitance, in contrast to the bipolar case. The gain can be made insensitive to temperature and IC processing. Experimental results demonstrating the feasibility of the concept are presented.