Body-tunable CMOS OTA for continuous-time analog filter applications

A linear fully-balanced CMOS operational transconductance amplifier (OTA) designed for high-frequency continuous;time filters is described. A CMOS transconductor circuit based on two cross-coupled differential nMOS pairs together with a negative resistance load for compensating the parasitic output resistance of the OTA is used. In contrast with existing techniques, the tuning capabilities with an adjustable floating voltage source connected to the body terminals of the input stage MOSFETs are examined. SPICE simulations results shows THD<1% at 1.7V with dynamic range equal to 71dB at a power consumption of 4.85mW from a single 6-V supply. Application to a bandpass filter in the high-frequency range is presented as an example, assuming implementation in a standard 2 mu m CMOS process (MOSIS). The centre frequency of the filter is tunable in the range of 3.5MHz - 28.2MHz.