I have an amplifier circuit with AGC. I am told that the AGC circuit attenuation of this amplifier can be determined from the voltage across a diode in the AGC circuit. As I understand it, the voltage across a diode is logarithmically related to the current, with the current, in this case directly related to the attenuation.

Problem is, I don't understand what I think I know about logarithmic & exponential functions.

What I ultimately want to do is:

- Measure the signal level out of the amplifier.

- Measure the voltage across the diode, & calculate the attenuation.

- From this, calculate the input signal level (I am actually only concerned with relative signal levels, not the absolute level of the input).

Here's what I measure:

Input Voltage Diode Voltage < 0.02 .4241 Quiescent voltage of diode with

1M bias resistor to 5V+ 0.02 .4242 The AGC is just starting to kick in at this point. 0.05 .4279 0.10 .4334 0.20 .4424 0.5 .4620 1.0 .4827 2.0 .5085 5.0 .5483 10.0 .5827 20.0 .6235Can anybody help me to understand where I need to go from here?

Thanks Scott Kelley