Log amplifiers

Updated March 12, 2010

New for February 2009! This page was requested by Chris

In a log amp, the output voltage is proportional to the log of the input voltage. Log amps are often used in radars, as the return signal varies as radius^4. The Log amp is the answer to the question, "what am I going to do with 100 dB of dynamic range?

One way to create a log amp is to configure limiting amplifiers in series, and sum the outputs. Like most solutions to a problem, this is not perfect.

We created a math model of such a log amplifer using Excel. Here there are four amplifiers, each with 20 dB gain, and a saturated outpiut power of 1 mW (0 dBm)

Everyone, feel free to help us out with some content here!

Log attenuator?