Frequency-selective integrated circuits using phase-lock techniques

A system-oriented approach to the design of inductorless tuned integrated circuits is described. This design method uses the phase-locked loop (PLL) techniques to obtain the desired tuning and interference-rejection characteristics. The PLL approach does not require tight control of component tolerances, and offers a higher selectivity and frequency capability than the corresponding active-RC synthesis methods. In this paper, basic design parameters for phase-locked integrated circuits are given, and two separate design examples are described. First is a high- frequency (1 to 25 MHz) FM amplifier/detector, which forms a monolithic replacement for the IF strip and the detector sections of a conventional FM receiver or TV sound system. The second is an integrated FM multiplex receiver for multi-channel telemetry applications, which has the selectivity of a 6-pole bandpass filter and can be tuned by means of an external resistor or capacitor from a fraction of a cycle to over 300 kHz.