CMOS operational transconductance amplifier for PRML read channel applications

A CMOS operational transconductance amplifier (OTA) for partial-response maximum-likelihood (PRML) read channel applications is presented. Using mismatched (or unbalanced) differential pairs to increase linear input range yields an additional benefit: a pole-zero cancellation, independent of tuning, which allows a high output impedance stage to be incorporated into the design. The OTA was designed using a standard 0.35 μm 3.3 V CMOS process-all simulation results presented use a supply voltage of 2.5 V. The maximum available linear input range is 250 mV_p-p at a unity-gain frequency of 100 MHz. The power consumption of the transconductor core and its associated folded-cascode output stage is 3 mW