LV opamp with programmable rail-to-rail constant-gm

In this paper a new differential pair architecture with programmable rail-to-rail constant-g_m is presented and incorporated into an opamp. Since the architecture adopts a signal processing method to obtain constant-g_m, it can be implemented in any complementary VLSI technology and it functions regardless of transistor operating regions. The experimental results of the proposed opamp show that the total transconductance is constant at any common mode input voltage (CMR) and programmed over very wide range simply by varying the bias current of the opamp. It is also shown that constant unity gain frequency and open loop gain are obtained at any CMR and total harmonic distortion is effectively reduced due to the constant-g_m