Patent ID: 6958655

Claim:
A variable gain amplifier circuit using a variable impedance circuit, comprising: an input terminal; an operational amplifier; a first variable impedance connected with the input terminal and a reverse input terminal of the operational amplifier; a second variable impedance connected with the reverse input terminal of the operational amplifier and an output terminal of the operational amplifier; a third variable impedance whose first end is connected with the reverse input terminal of the operational amplifier; a fourth variable impedance whose first end is connected with the input terminal and whose second end is connected with a second end of the third variable impedance; and a fifth variable impedance whose first end is connected with the second end of the third variable impedance and whose second end is connected with the output terminal of the operational amplifier, wherein the first variable impedance, the second variable impedance, and the third variable impedance are controlled in accordance with an upper bit group; and wherein the fourth variable impedance and the fifth variable impedance are controlled in accordance with a lower bit group.