Design and applications of rail-to-rail FC-OTA and second-generation CCII+ cell

This chapter presents an ultra-low-power folded cascode bulk-driven voltage to current converter, also called an operational transconductance amplifier (OTA), operating in weak inversion or subthreshold region. This folded cascode bulk-driven OTA provides nearly rail-to-rail input common mode range, enough 3-dB bandwidth and gain bandwidth product to process low-amplitude and low-frequency biosignals with sub-100 nW power dissipation. This designed OTA has been employed for multifunction single-input multiple-output and multiple-input single-output type biquadratic filters, notch filters, oscillators, integrators, adders, instrumentation amplifiers, and wave-shaping circuits. This FC-BD-OTA has been converted to a dual-output second-generation current conveyor (CCII+) cell useable for the design of various LV-LP and low-frequency voltage as well as current mode circuits. This designed CCII+ cell has been employed to design biquadratic filters, current mode instrumentation amplifier, analog signal adder, biphase, and three-phase oscillators as well as in some wave-shaping circuits. These applications are designed to process low-frequency (100 mH–500 Hz) biomedical signals. Appendix 1 briefly introduces another symmetric current mirror self-cascode load bulk-driven OTA having three output nodes, which has been utilized to design full wave rectifiers. All these circuits and subcircuits have been designed and simulated in standard n-tub-bulk 180 nm complementary metal oxide semiconductor process technology using Tanner EDA simulator tool of version 16.1.