A simple low voltage current sense amplifier with switchable input transistor

A simple SRAM current sense amplifier with common gate input stage is presented. Instead of keeping the gate at constant potential it is controlled by the select signal of the bit line multiplexer (MUX). If the transistor is turned on it maintains a low input resistance while the off-state is used for multiplexing and power down. Experimental results in 0.18µm 1.8V CMOS show that the circuit is superior to conventional voltage sensing. It is shown that for supply voltages below IV where the driving cell currents become very small, only current sensing is capable of fast reading. For a 0.12µm technology the simulated lower supply voltage limit of the proposed circuit is as low as 0.4V.