Piezoelectric oscillator
View Patent ↗A piezoelectric oscillator includes: a piezoelectric resonator; an oscillation circuit including a variable resistance circuit and a transistor for oscillation; a constant current circuit, the constant current circuit including a first current mirror circuit, and a current control circuit having an output terminal and controlling a current flowing in the first current circuit so as to enable an output current of the constant current circuit to be adjusted, the output terminal of the first current mirror circuit being coupled to at least one of a collector and a base of the transistor for oscillation with the variable resistance circuit; and a control circuit coupled to the current control circuit and the variable resistance circuit, the control circuit controlling the current control circuit and a resistance value of the variable resistance circuit.
1. A piezoelectric oscillator, comprising:
a piezoelectric resonator;
an oscillation circuit including a variable resistance circuit and a first transistor for oscillation;
a constant current circuit, the constant current circuit including a first current mirror circuit having an output terminal, and a current control circuit controlling a current flowing in the first current mirror circuit so as to enable an output current of the constant current circuit to be adjusted, the output terminal of the first current mirror circuit being coupled to at least one of a first terminal and a control terminal of the first transistor; and
a control circuit coupled to the current control circuit and the variable resistance circuit, the control circuit controlling the current control circuit and a resistance value of the variable resistance circuit, wherein:
the control circuit includes a switch circuit,
the constant current circuit further includes a constant current source,
the current control circuit is configured as a second current mirror circuit including a second transistor receiving an output current of the constant current source, and a plurality of mirror transistors coupling to the second transistor as a current mirror connection,
the plurality of mirror transistors are coupled parallel each other and coupled to the first current mirror circuit, and
the switch circuit is provided between a reference potential and second terminals of each of the plurality of mirror transistors.
2. The piezoelectric oscillator according to claim 1 , wherein the oscillation circuit is configured as a Pierce oscillation circuit.
3. The piezoelectric oscillator according to claim 1 , wherein the oscillation circuit is configured as a Colpitts oscillation circuit.
4. The piezoelectric oscillator according to claim 1 , wherein the variable resistance circuit includes a plurality of parallel-connected circuits coupled in series, each of the plurality of parallel-connected circuits including a resistor and a switch that are coupled in parallel.
5. The piezoelectric oscillator according to claim 1 , wherein the variable resistance circuit includes a plurality of series-connected circuits coupled in parallel, each of the plurality of series-connected circuits including a resistor and a switch that are coupled in series.
6. The piezoelectric oscillator according to claim 1 , wherein the switch circuit includes a plurality of circuits each having a resistor and a switch coupled in series with the resistor, each of the plurality of circuits coupling to one of the plurality of mirror transistors.
7. The piezoelectric oscillator according to claim 1 , further comprising a circuit portion that is fabricated as an integrated circuit, the circuit portion including the oscillation circuit, the constant current circuit, and the control circuit, and excluding the piezoelectric resonator.
8. The piezoelectric oscillator according to claim 1 , wherein the variable resistance circuit is coupled between the first terminal of the first transistor and the control terminal of the first transistor.