Voltage-controlled oscillator having short synchronous pull-in time

摘要

A voltage-controlled oscillator includes a control terminal having a control voltage applied thereto, first and second output terminals, first and second ring oscillators, first and second output buffer circuits, and a latch circuit. The first and second ring oscillators include odd numbers of inverting amplifier circuits in series, a transfer gate circuit connected between the inverting amplifier circuits, and a resistor connected in parallel to the transfer gate circuit. The transfer gate circuit includes a transfer transistor connected between the inverting amplifier circuits, and has a transistor control terminal connected to the control terminal. The first and second output buffer circuits have inputs connected to the first and second ring oscillators, and outputs connected to the first and second output terminals. The latch circuit is connected to the first and second ring oscillators. The latch circuit controls the first and second ring oscillators to output complementary oscillation signals.