variable gain amplifiers(VGA)

[pjames_e]

how to choose a VGA and how to use it......
can it be use as a voltage negative gain.

 

[flamingo]

Gain control range, maximum and mimum gain, bandwidth etc are the most important paramters of a VGA. Which kind of VGA depends on your application.
what do you mean "voltage negative gain"?

 

[pjames_e]

i mean lessen the input voltage to only 10%

 

[flamingo]

attenuate to 10% of input signal, that is -20dB gain. Just select the minimum gain less than -20, and the needed gain range. There are several types of VGA that satisfied you, and AnalogDevice is a good choice. You can find them from its homepage.