A CMOS OTA for HF filters with programmable transfer function

A CMOS operational transconductance amplifier (OTA) for programmable HF filters is presented. When used in an OTA-C integrator, the unity-gain frequency phase error remains less than 0.3° for frequencies up to more than one tenth of the OTA bandwidth. The OTA has built-in phase compensation, which allows tuning of the transconductance of the OTA (Gm) while maintaining a small phase error. Since this phase error is preserved over the Gm range of the OTA, the OTA is suitable for filters with a programmable transfer function. Using stacked square-law transistors improves the linearity, DC-gain, and power-consumption properties of the OT