A positive feedback-based op-amp gain enhancement technique for high precision applications

A power-efficient, voltage gain enhancement technique for op-amps has been described. The proposed technique is robust against Process, Voltage, and Temperature (PVT) variations. It exploits a positive feedback-based gain enhancement technique without any latch-up issue, as opposed to previously proposed conductance cancellation techniques. In the proposed technique, four additional transconductance-stages (gm stages) are used to boost the gain of the main gm stage. The additional gm stages do not significantly increase the power dissipation. A prototype was designed in 65nm CMOS technology. It results in 81dB voltage gain, which is 21dB higher than the existing gainboosting technique. The proposed opamp works with as low a power supply as 0.8V, without compromising the performance, whereas the traditional gain-enhancement techniques start losing gain below a 1.1V supply. The circuit draws a total static current of 295μA and occupies 5000μm2 of silicon area