Design of a programmable OTA with multi-decade transconductance adjustment

A programmable operational transconductance amplifier (OTA) structure is presented which permits a g_m adjustment by greater than two decades without severe degradation in linearity. This is achieved by including a programmable current mirror structure in the OTA output stage for coarse g_m adjustment in addition to a fine g_m adjustment via control of a bias current in the OTA differential input stage. Experimental results indicate that less than 1% nonlinearity in the transconductance characteristic is achieved throughout the g_m adjustment range for input signals less than 1$iV_pp