| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a variable gain amplifier which is comprised of MOS transistors and capable of implementing a gain control of exoponential function relative to a gain control signal. SOLUTION: The variable gain amplifier is configured such that it has a control signal conversion circuit 11 for converting a first gain control signal Vc to a second gain control signal Vy in accordance with a transfer characteristic, Vy=Vt.1n exp(b.Vc/Vt)-1} (Vt: temperature voltage, b>0), and a gain control circuit 12A in which gain is controlled by the second gain control signal Vy, and gain is varied in a manner of exponential function relative to the first gain control signal Vc; the gain control circuit 12A is comprised of a differential transistor pair comprising MOS transistors M1, M2 operating in a weak inversion area; input current Iin is input to a common source terminal of the transistors M1, M2 and a second gain control signal Vy is input between gate terminals; and output signal current I out is outputted from a drain terminal of the transistor M1.</p> |
