VARIABLE GAIN AMPLIFIER CIRCUIT AND ITS CONTROL CIRCUIT

摘要

PROBLEM TO BE SOLVED: To widely compensate temperature dependence of gain of a variable gain amplifier circuit. SOLUTION: Input control voltage VINfor gain control inputted in a control voltage compensation circuit 1 is converted into input control current IINcorresponding to the input control voltage VINby a resistor Rx and the input control current IINis inputted in a control current compensation circuit 2. The control current compensation circuit 2 compensates the input control current IINby generating and outputting control current IOUTof a value obtained by multiplying the input control current IINby a coefficient approximately proportional to absolute temperature T. The control current IOUTafter compensation by the control current compensation circuit 2 is converted into control voltage VOUTcorresponding to the control current IOUTby an operational amplifier OP and a resistor Ry and the control voltage VOUTis outputted from the control voltage compensation circuit 1. Thus, inclination of the control voltage VOUTfor the input control voltage VINis varied according to the absolute temperature T. COPYRIGHT: (C)2006,JPO&NCIPI