Fully Differential Operational Transconductance Amplifiers (OTAs).- Weak Inversion MOS Varactors for Tunable Integrators.- A 0.5 V 5th-Order Low-Pass Elliptic Filter.- A 0.5 V Track-and-Hold (T/H) Circuit.- A 0.5 V Continuous-Time Modulator.- 0.5 V Receiver Front-End Circuits.