AGC LNA design

[Leiser]

Hi,

does anyone know where I can find documentation about how to implement a LNA with AGC? I need this for a commercial FM receiver LNA. Since now I had a LNA without AGC but I would need to include the control as an independent block.

I guess the block diagram for this AGC is something like a coupler and comparator. But I would need a complete schematic to get to know how it is implemented.

Thanks in advance.

 

[logbook]

Typcially you would use a variable gain amplifier (VGA) and a detector. The detector output then controls the VGA. Typically the VGA stage is not the first stage in the LNA chain and not the last stage in the LNA chain, but somewhere in between. The reason is to keep the noise low without overloading the VGA.

Depending on noise requirements and signal requirements the position of the VGA relative to other stages will change.

 

[Leiser]

Logbook,

thanks for your comments. I´ll keep you inform of my progress!.