| 摘要 |
PURPOSE:To realize a variable gain control circuit representing effective logarithmic linear control by combining a divider and an adder/substractor to contitute a basic circuit and coupling said basic circuits in multi-stage. CONSTITUTION:The divider 1 consists of a fixed resistor R44, a variable resistor R45 and an operational amplifier A1, and the adder/subtractor 2 consists of fixed resistors R41, R42, R43 and an operational amplifier A2. The basic circuit is suitable for the variable gain control circuit between +25dB and -25dB and the variable gain control circuit coupling the basic circuits in two-stage in series is suitable for the variable gain control circuit between +40dB and -40dB. |
