A HIGH-ACCURACY CMOS OVERSAMPLING SWITCHED-CURRENT SAMPLE HOLD (S/H) CIRCUIT USING FEEDFORWARD APPROACH/

This brief presents a CMOS oversampling current sample/hold (S/H) circ uit using feedforward approach. The circuit adopts an integrating feed back structure which reduces the possible errors of the current copier used to sample the input current, due to clock feedthrough, channel-l ength modulation and capacitive feedback. The feedforward significantl y reduces the output swing of the integrator and thus improves the sta bility and accuracy of the circuit. As a result, high accuracy is obta ined with only first-order integration and a low oversampling ratio, a nd the useful bandwidth is enlarged. Simulation results show a 90-dB s ignal-to-distortion ratio, which is more than 20-dB improvement over a simple current copier, where the SCDN20 2-mu m CMOS process and 3.3-V supply voltage are assumed.