US Patent No. 10,291,235

OVEN CONTROLLED CRYSTAL OSCILLATOR


Patent No. 10,291,235
Issue Date May 14, 2019
Title Oven Controlled Crystal Oscillator
Inventorship Junichi Arai, Saitama (JP)
Assignee NIHON DEMPA KOGYO CO., LTD., Tokyo (JP)

Claim of US Patent No. 10,291,235

1. An oven controlled crystal oscillator, comprising:a crystal oscillator that includes a crystal resonator and an oscillator circuit;
a temperature control circuit including:
a heater resistor that has one end to which a supply voltage connects to generate a heat;
a thermistor configured to output a voltage to one end, the voltage corresponding to a temperature;
a first resistor that has one end to which the supply voltage is supplied and another end connected to the one end of the thermistor;
a second resistor that has one end to which the supply voltage is supplied;
a third resistor that has one end connected to another end of the second resistor and another end of the third resistor is grounded;
a differential amplifier that has one input terminal and another input terminal, a voltage between the another end of the first resistor and the one end of the thermistor being input to the one input terminal, a voltage between another end of the second resistor and the one end of the third resistor being input to the another input terminal, the differential amplifier amplifying a difference between the voltage input to the one input terminal and the voltage input to the another input terminal so as to output as a control voltage;
a thermosensor disposed in parallel to the first resistor, the thermosensor having one end to which the supply voltage is supplied; and
a fourth resistor that has one end connected to another end of the thermosensor and another end of the fourth resistor is grounded; and
a control integrated circuit that includes a digital variable resistor and a controller, the digital variable resistor being connected to the thermosensor in parallel, the controller adjusting a resistance value of the digital variable resistor based on a digital control signal input from outside.