Ping-Pong Operated Inverter-based OTA using Correlated Level Shifting Technique

This paper presents an inverter-based operational transconductance amplifier (OTA) which obtains high loop gain by correlated level shifting (CLS) technique with ping-pong operation. Thanks to the shifting capacitor providing voltage step between the OTA output and the inverter output, the suppressed inverter output swing helps OTA to achieve higher DC gain yielding better accuracy in the application of charge amplifier or integrator. The proposed technique utilizes two identical sub-OTA structures working in the ping-pong way to provide level shifting reference voltage for each other. This operation allows inverter-based OTA to work at the amplification mode in both clock phases, thus double sampling technique can be adopted to achieve twice of the charge transfer efficiency. Compared with the conventional inverter-based charge amplifier, the proposed topology improves DC gain from 39dB to 71dB at the cost of 17% power consumption increase from 7.1µA to 8.6µA.