| 摘要 |
PURPOSE:To smooth the operation of an AGC circuit without being affected by a power supply, by using two PIN diodes having a variable linear resistance. CONSTITUTION:Both ends of a diode D1 are connected to gain control terminals T1 and T2 of an amplifier 1 via DC block capacitors C1 and C2 and the diode acts like a variable resistor adjusting the gain of the amplifier 1. The 2nd PIN diode D2 is inserted between the anode of the PIN diode D1 and a positive power supply +V with the same polarity. With this constitution, as the resistance value of the diode D1 increases with smaller AGC current, the resistance of the diode D2 is increased, allowing to reduce the gain sufficiently through the removal of effect of the power supply. Since the voltage drop of the D1 and D2 is small, the current value is increased so that the gain is sufficiently increased. |
