A CMOS 5-V analog front end for 9600-bit/s facsimile modems

A CMOS 9600-b/s facsimile-modem analog front end was designed with the consideration that it be capable of being fabricated on the same chip with digital signal processing circuits. To achieve the dynamic range required in the high-speed QAM (quadrature amplitude modulation) modem environment with a single 5-V power supply, a fully differential architecture is used. The die area is 23 kmil/SUP 2/ and the power consumption is only 35 mW. The experimental results show that 76-dB dynamic range is achieved from the fully differential bandpass filter. The zero crossing detector in the MF-1 detection block can normally operate with -50-dBm input signal.