| 摘要 |
PURPOSE:To control the setting of gains over a wide range easily by a digital value by calibrating the gain of a variable gain circuit on the basis of the set value of the gain by using a reference voltage. CONSTITUTION:A D/A converter 13A and an amplifier 12A generate a voltage VREF' coresponding to the product of a reference voltage VREF and a gain set value N on the basis of a set gain N by a gain control digital signal GS and inputs this voltage to one input of an analog comparing circuit 11A. Then, the output Q of an FF8 is set by a gain setting command signal CS and the contact of a switch 1 is switched to the side of the reference voltage VREF by its set signal. Then, the reference voltage VREF is led to the input of the variable gain circuit 2 and a voltage Vout (=KRXVREF) amplified by the gain KR controlled by the output voltage of the D/A converter 3 appears at the output of the circuit 2. This output Vout is inputted to the other input of the circuit 11A and compared with said voltage VREF which is already inputted to the other input. |
