SEMICONDUCTOR INTEGRATED CIRCUIT

摘要

PURPOSE:To enhance a purity of an output signal of a PLL synthesizer circuit by a method wherein a PLL control part and a voltage control oscillator are installed on a chip substrate so as to be separated in positions which are not faced in parallel and an isolation region is formed around the voltage control oscillator. CONSTITUTION:A PLL synthesizer circuit of a BiCMOS constitution is formed in a rectangular chip 1; a PLL operation part 2 constituted of a CMOS logic circuit is formed in one corner part; a prescaler 3 of an ECL constitution by a bipolar transistor is formed so as to be adjacent to one side of the PLL operation part 2. A phase comparator 4 of a CMOS constitution and a charging pump 5 of a bipolar constitution are formed so as to be adjacent to the other side of the PLL operation part 2. A VCO(voltage control oscillator) 6 of a bipolar constitution is formed in a diagonal position of the PLL operation part 2 inside the chip 1; an LPF(low-pass filter) 7 constituted as an external circuit is connected between the VCO 6 and the charging pump 5. A P-type layer is formed as an isolation region 8 around the VCO 6.