Voltage-controlled oscillator using current feedback network
View Patent ↗Provided is a voltage-controlled oscillator (VCO) using a current feedback network for use in a wireless communication terminal. The voltage-controlled oscillator has high input impedance and low output impedance, so that a degree of isolation from the external load is excellent, thereby preventing degradation of the Q-factor by the load in overall oscillation circuit. In the voltage-controlled oscillator of the present invention, an LC resonator is provided to generate positive feedback, and negative resistance may be obtained at a wider frequency range by tuning a varactor of the LC resonator. And a boosting inductor is inserted into the positive feedback loop to have a greater negative resistance, therefore it is possible to prevent a problem in which the oscillation does not occur due to the parasitic resistance components generated during circuit fabrication.
1. A voltage-controlled oscillator using a current feedback network, comprising:
a first transistor;
a second transistor having a base directly connected to an emitter of the first transistor and a collector connected to a base of the first transistor;
a varactor connected to the emitter of the first transistor and a ground;
an inductor connected to the emitter of the first transistor and the ground; and
a resistor connected to the collector of the second transistor and a voltage source,
wherein the voltage source and a collector of the first transistor are short-circuited, and
wherein the ground and an emitter of the second transistor are short-circuited.
2. The voltage-controlled oscillator according to claim 1 , wherein the collector of the first transistor and the voltage source are connected through an inductor.
3. The voltage-controlled oscillator according to claim 1 , wherein the collector of the first transistor and the voltage source are connected through a resistor.
4. The voltage-controlled oscillator according to claim 1 , wherein the emitter of the second transistor and the ground are connected through an inductor.
5. The voltage-controlled oscillator according to claim 1 , wherein an output is made at the emitter, the collector or the base of the first transistor.
6. A voltage-controlled oscillator using a current feedback network, comprising:
a first transistor;
a second transistor having a base directly connected to an emitter of the first transistor and a collector connected to a base of the first transistor;
a capacitor connected to the emitter of the first transistor and a ground;
a first resistor connected to the emitter of the first transistor and the ground; and
a second resistor connected to the collector of the second transistor and a voltage source,
wherein a collector of the first transistor and the voltage source are short-circuited, and
wherein an emitter of the second transistor and the ground are short-circuited.
7. The voltage-controlled oscillator according to claim 6 , further comprising a varactor connected to the emitter of the first transistor and the ground.
8. The voltage-controlled oscillator according to claim 6 , wherein the collector of the first transistor and the voltage source are connected through an inductor.
9. The voltage-controlled oscillator according to claim 6 , wherein the emitter of the second transistor and the ground are connected through an inductor.
10. A voltage-controlled oscillator using a current feedback network, comprising:
a first transistor;
a second transistor having a base directly connected to an emitter of the first transistor and a collector connected to a base of the first transistor;
a first varactor connected to the emitter of the first transistor and a ground;
a first resistor connected to the emitter of the first transistor and the ground;
a second varactor connected to a collector of the first transistor and a voltage source;
an inductor connected to the collector of the first transistor and the voltage source; and
a second resistor connected to the collector of the second transistor and the voltage source,
wherein an emitter of the second transistor and the ground are short-circuited.
11. The voltage-controlled oscillator according to claim 10 , wherein the emitter of the second transistor and the ground are connected through an inductor.
12. A voltage-controlled oscillator using a current feedback network, comprising:
a first transistor;
a second transistor having a base directly connected to an emitter of the first transistor and a collector connected to a base of the first transistor;
a first varactor connected to the emitter of the first transistor and a ground;
a resistor connected to the emitter of the first transistor and the ground;
a second varactor connected to the collector of the second transistor and a voltage source; and
an inductor connected to the collector of the second transistor and the voltage source,
wherein a collector of the first transistor and the voltage source are short-circuited, and
wherein an emitter of the second transistor and the ground are short-circuited.
13. The voltage-controlled oscillator according to claim 12 , wherein the collector of the first transistor and the voltage source are connected through an inductor.
14. The voltage-controlled oscillator according to claim 12 , wherein the emitter of the second transistor and the ground are connected through an inductor.
15. A voltage-controlled oscillator using a current feedback network, comprising:
an LC tank connected to a voltage source;
a first transistor having a collector connected to the LC tank;
a second transistor having a base connected to an emitter of the first transistor and a collector connected to a base of the first transistor and the LC tank;
a first capacitor connected to the emitter of the first transistor and a ground;
a first resistor connected to the emitter of the first transistor and the ground;
a first inductor connected to the emitter of the second transistor and the ground;
a third transistor having a collector connected to the LC tank;
a fourth transistor having a base connected to an emitter of the third transistor and a collector connected to a base of the third transistor and the LC tank;
a second capacitor connected to the emitter of the third transistor and a ground;
a second resistor connected to the emitter of the third transistor and the ground;
a second inductor connected to the emitter of the fourth transistor and the ground; and
varactors connected to the collectors of the first transistor and the second transistor.
16. The voltage-controlled oscillator according to claim 15 , wherein the LC tank comprises a first and second inductors connected to the voltage source, respectively, and a capacitor connected to the first and second inductors.