This is a design circuit for sensing amplitude. This circuit is similar peak detector. But the output won’t immediately follow the input peaking. Because the output follows the input peak slowly, averaging effect will be seen at the output. This is the figure of the circuit.
This circuit is work based on two IC’s, there are LM307 and LF351. Use 1% resistor for R1, R2, R3, and R4, and you can achieve negative and positive cycle difference of 0.5dB at the worst case. If you use 5% resistors then the difference between positive and negative cycle gain difference would be about 2dB (worst case). The averaging time constant will depend on R5-C2, you can change to other values if needed. [Circuit's diagram source: National Semiconductor Application Notes].
