Variable gain amplifier and receiver including the same

1. A variable gain amplifier comprising:

a gain controller configured to generate a gain control voltage;

a variable gain amplifying unit configured to amplify an input signal and a feedback signal by using a voltage gain that is proportional to the gain control voltage, and convert the amplified signal into a predetermined magnitude; and

an offset canceller configured to remove an offset from an output signal of the variable gain amplifying unit and output the offset removed result as the feedback signal,

wherein the variable gain amplifying unit comprises:

a gain control unit configured to determine the voltage gain in response to the gain control voltage and amplify the input signal and the feedback signal by using the voltage gain; and

an amplifier configured to amplify an output of the gain control unit to the predetermined magnitude.

2. The variable gain amplifier of claim 1 , further comprising a transconductance controller configured to control a transconductance value of the variable gain amplifying unit as a stable value.

3. The variable gain amplifier of claim 2 , wherein the transconductance controller is an auto tuning circuit.

4. The variable gain amplifier of claim 2 , wherein the transconductance controller is shared with at least one operational transconductance amplifier outside the variable gain amplifier.

5. The variable gain amplifier of claim 1 , wherein the gain control unit comprises:

a first transconductor unit cell configured to determine a first gain in response to the gain control voltage and amplify the input signal and the feedback signal by using the first gain; and

a plurality of second transconductor unit cells configured to determine a second gain in response to the gain control voltage and amplify an output of the first transconductor unit cell by using the second gain.

6. The variable gain amplifier of claim 5 , wherein the first transconductor unit cell comprises:

a first operational transconductance amplifier configured to receive the input signal through a first differential input terminal pair to amplify the input signal by a predetermined gain, and output an amplified input signal to a first differential output terminal pair, the amplified input signal being fed back to a second differential input terminal pair through a resistor connected to the first differential output terminal pair; and

a second operational transconductance amplifier configured to receive an output signal of the first operational transconductance amplifier and the feedback signal from the offset canceller through third and fourth differential input terminal pairs to amplify them by a predetermined gain, and output an amplified result through a second differential output terminal pair, the amplified result being fed back to the third differential input terminal pair through first and second voltage adjustors connected to the second differential output terminal pair.

7. The variable gain amplifier of claim 6 , wherein each of the first and second voltage adjustors comprises an active resistance element capable of adjusting a resistance value.

8. The variable gain amplifier of claim 6 , wherein each of the first and second voltage adjustors comprises a plurality of metal oxide semiconductor (MOS) transistors having current paths connected in series, and the gain control voltage adjusts levels of a gate voltage and a body voltage of the MOS transistors.

9. The variable gain amplifier of claim 1 , wherein the gain control unit is configured to amplify the input signal and the feedback signal up to a dynamic range that system specification requires.

10. The variable gain amplifier of claim 1 , wherein the amplifier is configured to amplify an output of the gain control unit up to a magnitude at which digital conversion efficiency is maximized in system specification.

11. A receiver comprising:

a transconductor type low pass filter configured to remove signal noise of a channel through filtering and output a filtered signal;

a variable gain amplifier configured to amplify the filtered signal up to a dynamic range that system specification requires and amplify an amplified result up to a magnitude at which digital conversion efficiency is maximized; and

an analog-to-digital converter configured to convert an output of the variable gain amplifier into a digital signal,

wherein the variable gain amplifier comprises:

a gain controller configured to generate a gain control voltage;

a variable gain amplifying unit configured to amplify an input signal and a feedback signal by using a voltage gain that is proportional to the gain control voltage, and convert the amplified signal into a predetermined magnitude of a signal; and

an offset canceller configured to remove an offset from an output signal of the variable gain amplifying unit and output the offset removed result as the feedback signal, and

wherein the variable gain amplifying unit comprises:

a gain control unit configured to determine the voltage gain in response to the gain control voltage and amplify the input signal and the feedback signal by using the voltage gain; and

an amplifier configured to amplify an output of the gain control unit to the predetermined magnitude.