Communication system is used in RF and microwave, LAN's, mobile phones, base station monitoring, surveillance, satellite communications, transmitter antenna and receiver antenna testing. A multi-stage limiting amplifier & Frequency Modulation or Frequency Shift Keying demodulator is used in a 455-kHz signal processor. On chip feed forward offset cancellation circuit uses limiting amplifier. A quadrature detector is used in the Frequency Modulation or Frequency Shift Keying demodulator, & detector is consist of phase built into the chip and a tank phase shifter external to the chip. Image Frequency signal processor consumes milli Watts, 2-V power supply, and sensitivity about 72 dBm with demodulation constants of 20 milli Volts / kilo Hz and 10-kHz deviation. The active area is 0.2 mm2 and it uses 0.3- micron digital Complementary MOS technology. Limiting amplifier used in communication system and wireless communication