logarithmic amplifier

13 Iogarithmic amplifier The performance of the operational amplifier, the circuit diagram of which is shown in figure 1, is best seen from its input/output charac- teristic shown in figure 2. For smal) input voltages, the amplification is high; when the input voltage rises, the amplification drops off and finally remains almost static for further increases in input voltage. Some applications of a logarithmic amplifier are: driving a graphic recorder in weather stations, and in remote control systems (for instance, to avoid a too sudden and strong deflection of a servo arm). When used in conjunction with other equipment, the logar- ithmic amplifier is very flexible: 835892 analogue instruments as well as a row of LEDs can be connected to its output. Operational amplifiers Al and A2 form a non-inverting pre-amplifier. As the input signal of A3 should not under any circumstances be- come negative, the input level of the circuit can be shifted with poten- tiometer Pl as required. At ...