GENERAL DESCRIPTION
This TDA8051 is a monolithic bipolar IC intended for Quadrature Phase Shift Key (QPSK) demodulation. It includes:
• Low noise RF and gain controlled amplifier
• Two matched mixers
• Symmetrical Voltage Controlled Oscillator (VCO) with 0 to 90° signal generator whose frequency is controlled by an integrated Phase Lock Loop (PLL) circuit.
• Two matched amplifiers for output base-band active filtering and output buffers

The gain control is produced by output level detection compared with an external pre-fixed reference. The PLL consists of:
• Divide by four preamplifier
• 12-bit programmable main divider
• Crystal oscillator with 8-bit programmable reference divider
• Phase/frequency detector combined with charge pump to drive tuning amplifier
• 30 V output

FEATURES
• High operating input sensitivity
• Gain controlled amplifier
• PLL controlled carrier frequency
• Low crosstalk between I and Q channel outputs
• 3-wire transmission bus
• 5 V supply voltage.

APPLICATIONS
• BPSK/QPSK demodulation.