TRANS-CONDUCTANCE CONTROL CIRCUIT OF RAIL-TO-RAIL DIFFERENTIAL INPUT STAGE OF OPERATIONAL AMPLIFIER TO OBTAIN CONSTANT TRANS-CONDUCTANCE

摘要

PURPOSE: A trans-conductance control circuit of rail-to-rail differential input stage of operational amplifier to obtain constant trans-conductance is provided to maintain constantly the trans-conductance by controlling current applied to a differential pair. CONSTITUTION: A trans-conductance control circuit includes an RTR differential input stage, a supply current unit, and a trans-conductance control unit. The RTR differential input stage(100) includes a first differential pair and a second differential pair. The supply current unit is connected to each source of the first and the second differential pairs. The trans-conductance control unit(200) senses a first gate-source voltage of the first differential pair and a second gate-source voltage of the second differential pair, compares the reference current with the current corresponding to the sum of the first gate-source voltage and the second gate-source voltage, and controls the flow of the current according to a compared result.