Patent ID: RE41598

Claim:
An impedance matching circuit for facilitating impedance matching between the characteristic impedance of a cable and the input impedance at the input terminal of a receiver for data transmission, said impedance matching circuit comprises comprising : a first transistor, including a power supply terminal, a control terminal and a load terminal, wherein said power supply terminal of said first transistor is connected to a voltage supply, and said load terminal of said first transistor is connected to an input terminal of said receiver; a second transistor, including a power supply terminal, a control terminal and a load terminal, wherein said power supply terminal of said second transistor is connected to said voltage supply, and said control terminal of said second transistor is connected to said control terminal of said first transistor; a resistor, wherein one terminal of said resistor is connected to said load terminal of said second transistor and the other terminal is connected to the ground; and a negative feedback control circuit, wherein an inverting input terminal of said negative feedback control circuit receives an adjustable reference voltage, a non-inverting input terminal of said negative feedback control circuit is connected to said load terminal of said second transistor, and an output terminal of said negative feedback control circuit is connected to said control terminal of said second transistor; wherein the equivalent resistance of said impedance matching circuit is kept equal to the resistance of the varied characteristic impedance of said cable by adjusting said reference voltage.