Amplification circuit, human body channel-based communication system including the same, and operation method thereof

1 . An amplification circuit comprising:

a first amplifier of two or more amplifiers configured to receive an external signal, and to perform first band pass filtering on the external signal to output a first filter signal; and

a second amplifier of two or more amplifiers configured to receive the first filter signal, and to perform second band pass filtering on the first filter signal to output a second filter signal, and

wherein a frequency pass bandwidth of the second band pass filtering is narrower than a frequency pass bandwidth of the first band pass filtering.

2 . The amplification circuit of claim 1 , wherein the first amplifier and the second amplifier do not include an inductor element.

3 . The amplification circuit of claim 2 , wherein the first amplifier is further configured to amplify the external signal with a first amplification degree to output the first filter signal, and the second amplifier is further configured to amplify the first filter signal with a second amplification degree to output the second filter signal, and

wherein the second amplification degree is greater than the first amplification degree.

4 . The amplification circuit of claim 3 , wherein the first amplifier includes:

a first input bias circuit configured to receive the external signal, and to perform first high pass filtering on the external signal to output a first bias signal; and

a first amplification stage configured to receive the first bias signal, and to perform first low pass filtering on the first bias signal to output the first filter signal, and

wherein a cutoff frequency of the first high pass filtering is less than a cutoff frequency of the first low pass filtering.

5 . The amplification circuit of claim 4 , wherein the first input bias circuit includes:

an input capacitor connected to a first node and receiving the external signal;

a first input resistor connected between a power supply voltage and the first node; and

a second input resistor connected between the first node and a ground node.

6 . The amplification circuit of claim 5 , wherein the first amplification stage includes:

a first amplification resistor connected between the first node and a second node;

a second amplification resistor and an amplification capacitor connected in parallel between the second node a third node; and

an amplifier having a first input terminal connected to the second node, a second input terminal connected to the ground node, and an output terminal connected to the third node.

7 . The amplification circuit of claim 6 , wherein the first and second input resistors and the first and second amplification resistors are variable resistors, and

wherein the input capacitor and the amplification capacitor are variable capacitors.

8 . The amplification circuit of claim 7 , wherein the cutoff frequency of the first high pass filtering is inversely proportional to a capacitance value of the input capacitor.

9 . The amplification circuit of claim 8 , wherein the cutoff frequency of the first low pass filtering is inversely proportional to a capacitance value of the amplification capacitor.

10 . The amplification circuit of claim 9 , wherein the first amplification degree is determined based on resistance values of the first amplification resistor and the second amplification resistor.

11 . A human body channel-based wireless communication system comprising

an amplification circuit which receives an external signal; and

a control circuit configured to receive the external signal and to generate a control signal for controlling the amplification circuit based on a frequency band of the external signal,

wherein the amplification circuit includes:

a first amplifier of two or more amplifiers configured to receive an external signal, and to perform first band pass filtering on the external signal to output a first filter signal; and

a second amplifier of two or more amplifiers configured to receive the first filter signal, and to perform second band pass filtering on the first filter signal to output a second filter signal, and

wherein a frequency pass bandwidth of the second band pass filtering is narrower than a frequency pass bandwidth of the first band pass filtering.

12 . The wireless communication system of claim 11 , wherein the first amplifier and the second amplifier do not include an inductor element.

13 . The wireless communication system of claim 12 , wherein the first amplifier is further configured to amplify the external signal with a first amplification degree to output the first filter signal, and the second amplifier is further configured to amplify the first filter signal with a second amplification degree to output the second filter signal, and

wherein the second amplification degree is greater than the first amplification degree.

14 . The wireless communication system of claim 13 , wherein the first amplifier includes:

a first input bias circuit configured to receive the external signal, and to perform first high pass filtering on the external signal to output a first bias signal; and

a first amplification stage configured to receive the first bias signal, and to perform first low pass filtering on the first bias signal to output the first filter signal, and

wherein a cutoff frequency of the first high pass filtering is less than a cutoff frequency of the first low pass filtering.

15 . The wireless communication system of claim 14 , wherein the first input bias circuit includes:

an input capacitor connected to a first node and receiving the external signal;

a first input resistor connected between a power supply voltage and the first node; and

a second input resistor connected between the first node and a ground node.

16 . The wireless communication system of claim 15 , wherein the first amplification stage includes:

a first amplification resistor connected between the first node and a second node;

a second amplification resistor and an amplification capacitor connected in parallel between the second node a third node; and

an amplifier having a first input terminal connected to the second node, a second input terminal connected to the ground node, and an output terminal connected to the third node.

17 . The wireless communication system of claim 16 , wherein the first and second input resistors and the first and second amplification resistors are variable resistors, and the input capacitor and the amplification capacitor are variable capacitors, and

wherein the frequency pass bandwidth of the first band pass filtering is adjusted by adjusting resistance values of the variable resistors and capacitance values of the variable capacitors included in the first amplifier based on the control signal.

18 . A method of operating a human body channel-based wireless communication system including an amplification circuit which includes a first amplifier of two or more amplifiers configured to receive an external signal and to perform first band pass filtering on the external signal to output a first filter signal and a second amplifier of two or more amplifiers configured to receive the first filter signal and to perform second band pass filtering on the first filter signal to output a second filter signal, the method comprising:

receiving the external signal;

determining a frequency band of the external signal;

adjusting a frequency pass bandwidth of the first band pass filtering and a frequency pass bandwidth of the second band pass filtering by adjusting resistance values of variable resistors and capacitance values of variable capacitors included in each of the first amplifier and the second amplifier based on the frequency band of the external signal; and

generating, an amplified signal based on the first filter signal, the second filter signal and the external signal, and

wherein the first amplifier and the second amplifier do not include an inductor element, and the frequency pass bandwidth of the second band pass filtering is narrower than the frequency pass bandwidth of the first band pass filtering.