A synchronous phase-lock loop detector for integrated AM radio

A synchronous phase-lock loop AM detector has been realized on a single chip in a bipolar process with an f/SUB T/ of 400 MHz. The circuit accepts input signals at an IF frequency of 450-500 kHz with effective values between 20 and 100 mV. The phase-lock loop capture range is about 150 kHz. AM signals with over 80% modulation depth can be demodulated with less than 1% harmonic distortion in the audio output signal. The power dissipation of the chip is 120 mW at 8 V. The total chip size is 1900/spl times/1300 /spl mu/m/SUP 2/. Since the VCO and the 90/spl deg/ phase shift are completely realized on-chip, large signals at the IF frequency do not occur at the pins of the IC, and parasitic feedback of such signals to the IF amplifier input is minimized.