A Continuous-Time Programmable Digital FIR Filter

In this paper, we describe the design and implementation of a continuous-time finite-impulse-response processor chain, which includes a 6-bit asynchronous ADC, an asynchronous digital core, and an 8-bit asynchronous DAC designed in TSMC 0.25-mum technology. The continuous-time, discrete-amplitude systems combine benefits associated with analog and digital systems. Discrete-amplitude representations leverage the noise immunity and robustness of digital implementations. Continuous-time, nonsampled operation prevents aliasing and reduces the in-band quantization noise associated with the aliasing of subharmonic components. We present measurement results demonstrating an audio low-pass filter with a bandwidth of 6.0 kHz