The SP5070 is a single modulus frequency synthesiser for use in Satellite TV receivers and together with an appropriate voltage controlled oscillator (VCO), forms a complete phase locked loop (PLL) synthesiser. The circuit consists of a prescaler with preamplifier and a fixed modulus divider. The phase comparator is fed with a reference frequency derived from an external oscillator or crystal. The comparator has a charge pump output amplifier stage around which feedback may be applied. Only an external transistor is required for varicap line driving.