Automatic level control (ALC)

Anybody how to build one using a gual gate fet and a diode detector. Freq rance 0-500 MHz.

I'm thinking to make a tap at the output and feed it to the diode to get a DC voltage, then maybe add an op-amp or two or maybe make a summing amp which should control the gain of the fet.

I'm using BF980 for the fet.

Appreciate any suggestions.

This is more general.Because is two gat,used one as a control.

To config the circuit as AGC. You may use the opanp as integer,and control the ibteger coefficient.