A 1.6 V 80 μW rail-to-rail constant-GM bipolar adaptive biased op-amp input stage

In the design of operational amplifiers, adaptive biasing topologies help to optimise the trade off between speed characteristics and power consumption. In fact, they give an output current dependent on the input differential voltage, minimising the stand-by current. All the adaptive biasing solutions presented in literature require an extra quiescent current and, consequently, an additional static power dissipation. In this paper, this problem is overcome by an innovative adaptive biasing topology, which is here proposed and utilized as an application to a traditional constant transconductance rail-to-rail input stage of a low-voltage (1.6 V) low-power (80 μW) bipolar operational amplifier