Voltage-current conversion circuit, a voltage-controlled oscillator, and a phase-locked loop circuit
The voltage-controlled oscillator can include a voltage-current conversion circuit that outputs a control current corresponding to the control voltage, and a ring oscillator that generates an output signal with a frequency corresponding to the control current. According to an embodiment, by using a voltage-current conversion circuit, it is possible to design a voltage-controlled oscillator that can operate even with a relatively low supply power and have stable characteristics even when the temperature changes.
1 . A voltage-controlled oscillator, comprising:
a voltage-current conversion circuit configured to receive a control voltage and output a control current corresponding to the control voltage; and
a ring oscillator configured to output an output signal with a frequency corresponding to the control current,
wherein the voltage-current conversion circuit comprises:
a first circuit configured to output a first current corresponding to the control voltage;
a second circuit configured to output a second current corresponding to a reference voltage; and
a third circuit configured to output the control current based on the first current and the second current,
wherein the second circuit is a replica circuit of the first circuit, and
wherein the third circuit is configured to form a current mirror with the second circuit to output a third current corresponding to the second current, and the third circuit is configured to output the control current based on the first current and the third current.
2 . The voltage-controlled oscillator of claim 1 , wherein the control current is generated based on a difference between the first current and the third current.
3 . The voltage-controlled oscillator of claim 2 , wherein the reference voltage is a preset voltage.
4 . The voltage-controlled oscillator of claim 1 , wherein the first circuit comprises a first NMOS transistor having a gate terminal through which the control voltage is input, and
the second circuit comprises a second NMOS transistor having a gate terminal through which the reference voltage is input.
5 . The voltage-controlled oscillator of claim 4 , wherein the first NMOS transistor and the second NMOS transistor have the same temperature characteristics.
6 . A voltage-current conversion circuit, comprising:
a first circuit configured to receive a control voltage and output a first current corresponding to the control voltage;
a second circuit configured to receive a reference voltage and output a second current corresponding to the reference voltage; and
a third circuit configured to output a control current corresponding to the control voltage based on the first current and the second current,
wherein the second circuit is a replica circuit of the first circuit, and
wherein the third circuit is configured to form a current mirror with the second circuit to output a third current corresponding to the second current, and the third circuit is configured to output the control current based on the first current and the third current.
7 . The voltage-current conversion circuit of claim 6 , wherein the control current is generated based on a difference between the first current and the third current.
8 . The voltage-current conversion circuit of claim 7 , wherein the reference voltage is a preset voltage.
9 . The voltage-current conversion circuit of claim 6 , wherein the first circuit comprises a first NMOS transistor having a gate terminal through which the control voltage is input, and
the second circuit comprises a second NMOS transistor having a gate terminal through which the reference voltage is input.
10 . The voltage-current conversion circuit of claim 9 , wherein the first NMOS transistor and the second NMOS transistor have the same temperature characteristics.
11 . A phase-locked loop circuit, comprising:
a phase detector configured to detect a phase difference between a first input signal and a second input signal;
a filter configured to charge or discharge based on the phase difference;
a voltage-current conversion circuit configured to output a control current corresponding to a control voltage applied to the filter; and
an oscillator configured to output an output signal with a frequency corresponding to the control current,
wherein the voltage-current conversion circuit comprises:
a first circuit configured to output a first current corresponding to the control voltage;
a second circuit configured to output a second current corresponding to a reference voltage; and
a third circuit configured to output the control current based on the first current and the second current,
wherein the second circuit is a replica circuit of the first circuit, and
wherein the third circuit is configured to form a current mirror with the second circuit to out-put a third current corresponding to the second current, and the third circuit is configured to output the control current based on the first current and the third current.
12 . The phase-locked loop circuit of claim 11 , wherein the control current is generated based on a difference between the first current and the third current.
13 . The phase-locked loop circuit of claim 11 , wherein the second input signal corresponds to the output signal of the oscillator.
14 . The phase-locked loop circuit of claim 11 , wherein the oscillator comprises a ring oscillator.