Crystal oscillation circuit

Abstract

Abstract PURPOSE:To attain slow changing of an oscillated frequency by providing plural sets of series connections each comprising a capacitor and a varactor diode having a resistor at their connecting point in parallel, connecting a crystal resonator to an external terminal of an TC of CMOS structure and impressing a control voltage to the varactor diode via the resistor. CONSTITUTION:A capacitor is connected in series with varactor diodes 9-1-9-n respectively of the same shape, resistors 9-1-9-n are provided at each connecting point, control voltages 10-1-10-n are impressed to change the capacitance of the varactor diodes 9-1-9-n. The temperature compensation circuit comprising the capacitors, varactor diodes and resistors is assembled in the inside of the CMOS IC and the capacitors 7-1-7-n are connected to the gate of the oscillation inverter 1. When the control voltage 10-1 is switched from L to H level, the voltage impressed to the varactor diode 9-1 rises with a delay by a time constant comprising the resistor 8-1 and the capacitance of the varactor diode 9-1. Thus, the capacitance changes slowly and also the oscillation frequency changes slowly.

Inventors

• 👤 Takashi Takeuchi
• 👤 隆 竹内

Bibliographic Details