rf vga

The VGA is operated at below 10MHz. 0.5dB gain step and 0.1dB accuracy.
I have no idea how to implement it.. The accuracy spec is so tough.

Hi
One idea ---- use digital control

Regards

I have to implement it in analog domain circuit.
I can't really figure out why digital control can help me.

Hi
The gain(control voltage,temperature) dependence is nonlinear in common case
You can store this dependence in memory and then control your amp
It will be digital controled amplifier exactly.

Regards

Thanks, but I still have the questions.
how about the design of VGA? How do I make it perform accurate gain?
The often used method of VGA is ..?

To make digital VGA accurate use the matching principle in IC process!

The idea is to switch between different matched devices in a process to define the gain. The simplest form is an opamp configuration. If the gain at target frequency is high enough the gain could be simply defined by switched resistors.

But you did not mention if the VGA applies to RF or IF!

The VGA is used for several MHz application.

use cascaded fully differetial op
there are lots papers describes about it .
you can search it .
good luck.