On the design of highly linear CMOS digitally programmable operational transconductance amplifiers for low and high-frequency applications

This paper proposes a novel highly linear digitally programmable fully differential operational transconductance amplifier (DPOTA) circuit. Two versions of the proposed DPOTA structure are designed. The first version is optimized for high-frequency operation with current division networks designated to 3-bit control code words. On the other hand, the second version is optimized for low-frequency operation with 4-bit control code words. The third-order harmonic distortion (HD3) of the first DPOTA version remains below - 66 dB up to 0.4V differential input voltage at 10 MHz frequency. The second DPOTA version achieved HD3 of - 70dB with an amplitude of 20 mV(p-p) and at 100Hz frequency. The proposed circuits are designed and simulated in 90 nm CMOS model, BSIM4 (level 54) under a balanced 1.2 V supply voltage.