A constant GM rail-to-rail opamp with a novel input stage for BiCMOS process

AbstractA BiCMOS rail-to-rail operational amplifier capable of operating from supply voltages as low as 1.W is presented. A new technique of achieving a rail-to-rail input common mode range us'ing a bipolar input stage is developed. The new technique avoids the use of complementary pairs at the input and thus avoids complicated schemes for monitoring the constant g,?, . The resulting variation of the g?,, is within +/-5.64%. The output stage is also rail-to-rail with a class AB control providing 5ma of current to a 300 Ohm resistor in parallel with a l 0 p F load. The output stage can swing to within 50mV of each supply rail. The opamp was realized in a conventional I .3pm BiCMOS process with a DC gain of SldB and a unity gain frequency of 7.9 MHz.