MOS varactor and voltage-controlled oscillator using the same
View Patent ↗To provide a MOS varactor in which oscillation frequency variation is small and variation in a capacitance changing voltage is small, and a voltage-controlled oscillator using the MOS varactor, as a load capacitor of an oscillating circuit composed of a feedback resistor 1 , an amplifier 2 , and a crystal vibrator 3 , a variable electrostatic capacitor, which is generated between drain/source terminals and a gate terminal of each of MOS transistors 5 a and 6 a each of which source and drain terminals are short-circuited, is connected. A bulk terminal of each of the MOS transistors 5 a and 6 a is connected to one terminal of a resistor 19 , a voltage is applied to the other terminal of the resistor 19 , the bulk terminal of each of the MOS transistors 5 a and 6 a is connected to one terminal of a capacitor 20 , and the other terminal of the capacitor 20 is grounded.
1. A MOS varactor using a capacitive component generated between terminals of a MOS transistor, comprising:
a resistor which has one end connected to a back gate terminal and the other end grounded,
wherein a control voltage is applied to a gate terminal such that an electrostatic capacitance between source/drain terminals and the back gate terminal can vary and an electrostatic capacitance between the source/drain terminals and the gate terminal can vary.
2. A MOS varactor using a capacitive component generated between terminals of a MOS transistor, comprising:
a capacitor which has one end connected to a back gate terminal and the other end grounded,
wherein a control voltage is applied to a gate terminal such that an electrostatic capacitance between source/drain terminals and the back gate terminal can vary and an electrostatic capacitance between the source/drain terminals and the gate terminal can vary.
3. A MOS varactor using a capacitive component generated between terminals of a MOS transistor, comprising:
a resistor which has one end connected to a back gate terminal,
a variable voltage source connected to the other end of the resistor, and
a capacitor which has one end connected to the back gate terminal and the other end grounded,
wherein a control voltage is applied to a gate terminal such that an electrostatic capacitance between source/drain terminals and the back gate terminal can vary and an electrostatic capacitance between the source/drain terminals and the gate terminal can vary.
4. A voltage-controlled oscillator comprising:
the MOS varactor according to claim 1 ,
an amplifier having an inverter and a feedback resistor, and
a piezoelectric vibrator having two terminals with the MOS varactor connected therebetween,
wherein the MOS varactor includes first and second MOS transistors each of which source/drain terminals are short-circuited, and an electrostatic capacitance is generated between the source/drain terminals and a gate terminal of each of the first and second MOS transistors, and
an oscillation frequency of the MOS varactor is controlled by a control signal input to the gate terminal of each of the first and second MOS transistors.
5. A voltage-controlled oscillator comprising:
the MOS varactor according to claim 2 ,
an amplifier having an inverter and a feedback resistor, and
a piezoelectric vibrator having two terminals with the MOS varactor connected therebetween,
wherein the MOS varactor includes first and second MOS transistors each of which source/drain terminals are short-circuited, and an electrostatic capacitance is generated between the source/drain terminals and a gate terminal of each of the first and second MOS transistors, and
an oscillation frequency of the MOS varactor is controlled by a control signal input to the gate terminal of each of the first and second MOS transistors.
6. A voltage-controlled oscillator comprising:
the MOS varactor according to claim 3 ,
an amplifier having an inverter and a feedback resistor, and
a piezoelectric vibrator having two terminals with the MOS varactor connected therebetween,
wherein the MOS varactor includes first and second MOS transistors each of which source/drain terminals are short-circuited, and an electrostatic capacitance is generated between the source/drain terminals and a gate terminal of each of the first and second MOS transistors, and
an oscillation frequency of the MOS varactor is controlled by a control signal input to the gate terminal of each of the first and second MOS transistors.
7. A voltage-controlled oscillator comprising:
the MOS varactor according to claim 1 ,
an amplifier having an inverter and a feedback resistor, and
a piezoelectric vibrator having two terminals with a variable capacitive means, which includes the MOS varactor and first and second DC-blocking capacitors, connected therebetween,
wherein the MOS varactor includes a MOS transistor each of which source/drain terminals are short-circuited, and an electrostatic capacitance is generated between the source/drain terminals and a gate terminal of the MOS transistor,
oscillating voltages with opposite phases are applied to the source/drain terminals and the gate terminal, respectively, and
an oscillation frequency of the MOS varactor is controlled by a control signal input to the gate terminal of each of the first and second MOS transistors.
8. A voltage-controlled oscillator comprising:
the MOS varactor according to claim 2 ,
an amplifier having an inverter and a feedback resistor, and
a piezoelectric vibrator having two terminals with a variable capacitive means, which includes the MOS varactor and first and second DC-blocking capacitors, connected therebetween,
wherein the MOS varactor includes a MOS transistor each of which source/drain terminals are short-circuited, and an electrostatic capacitance is generated between the source/drain terminals and a gate terminal of the MOS transistor,
oscillating voltages with opposite phases are applied to the source/drain terminals and the gate terminal, respectively, and
an oscillation frequency of the MOS varactor is controlled by a control signal input to the gate terminal of each of the first and second MOS transistors.
9. A voltage-controlled oscillator comprising:
the MOS varactor according to claim 3 ,
an amplifier having an inverter and a feedback resistor, and
a piezoelectric vibrator having two terminals with a variable capacitive means, which includes the MOS varactor and first and second DC-blocking capacitors, connected therebetween,
wherein the MOS varactor includes a MOS transistor each of which source/drain terminals are short-circuited, and an electrostatic capacitance is generated between the source/drain terminals and a gate terminal of the MOS transistor,
oscillating voltages with opposite phases are applied to the source/drain terminals and the gate terminal, respectively, and
an oscillation frequency of the MOS varactor is controlled by a control signal input to the gate terminal of each of the first and second MOS transistors.