| 摘要 |
PURPOSE:To secure the 1:1 correspondense between the automatic gain control voltage and the input signal level by controlling the amplification factor properties of the multi-step connection operational amplifier to the nonlinear properties and the reverse curvature properties of the automatic gain control intermediate frequency amplifier. CONSTITUTION:The parallel circuit of resistance 16 and diode 17 constitutes the negative feedback circuit. And diode 17 is turned on in the state under which the output voltage of operational amplifier 13 is higher than the voltage at the reverse input terminal 19, and the amplification factor of the negative feedback circuit is decided by the resistance of diode 17 and input resistance 15. In the opposite state, diode 17 is turned off, and the amplification factor is decided by feedback resistance 16 and resistance 15. Flection point V can be varied through control of variable resistance 14 for the input/output properties of the 1st-step amplifier circuit, and then inclined by varying resistances 15 and 16. With the vertical connection of several steps of the amplifier circuit, the input/output properties can be approximated to the curve. |
