A BiCMOS low distortion tunable OTA for continuous-time filters

The use of electronically programmable bipolar current mirrors in conjunction with a BiCMOS linearized input stage produces a linearized transconductance amplifier with an extended transconductance adjustment range. Both linearity and transconductance excess phase are largely independent of the transconductance gain over the range of adjustment. HSPICE results show that with a ±2.5-V power supply a decade of adjustment is obtained for a 2-V p-p input signal with less than 1% distortion, and from a simple phase compensation scheme the excess phase can be kept below 1° for up to 25 MHz. The tuning range and linear operation of a low-frequency version of the operational transconductance amplifier (OTA) were experimentally demonstrated using transistor array ICs