Log-amp performs advanced RF measurements

摘要

The basic purpose of a logarithmic amplifier (log-amp) is to convert an RF input signal to an output voltage proportional to the log of RF power. Modern log-amps accomplish this task with exceptional dynamic range, and their operation is simple. Inputs are single-ended or differential, and the detector outputs connect to the non-inverting terminal of an internal op-amp or transconductance amplifier. The integrated op-amp allows a user-adjustable slope and an easily implemented closed-loop operation for power-control applications. Output voltage is proportional to the log of the input power.