A Micropower Gate-Bulk Driven Differential Difference Amplifier with Folded Telescopic Cascode Topology for Sensor Applications

A micropower high-gain, low-noise differential difference amplifier (DDA) is presented in this paper. The new circuit incorporates the gate-bulk driven transistor pairs for input stage transconductance enhancement; the very high gain folded telescopic cascode structure that permits small headroom operation; and the replica tracking bias that sustains the circuit performance against variations of process, supply voltage and temperature. The DDA is designed using Global Foundries 1.8V/3.3V CMOS 0.18 mu m process and simulated using the BSIM3 models. The simulated results for the DDA shows DC gain of 131.4dB and unity gain bandwidth of 1.097 MHz at a load of 30pF//200k Omega while consuming quiescent current of 10.7 mu A at a single 1.8V supply. The proposed DDA gives noise reduction of 15.56% with respect to that of the gate-driven counterpart. It gives a noise efficiency factor (NEF) [ 1] of 6.7 when realizing a bio-potential sensing circuit. The low noise, very high gain, floating inputs, low power and robust features of the proposed DDA are suitable for front-end interface circuit in sensory systems.