George Herold wrote: : I don't suppose anyone has a link/ reference to an article that shows : an actual circuit. I've been trolling the web with no luck. It's
Like Jeroen said its quite simple. Take an inverting amplifier with a gain of, say, 10 V/V. Then connect a feedback resistor of
500ohms across it. Now look at the amp input (I'm too tired to mind A-1 vs. A): it looks like a 50 ohm resistor with 1/10 of the noise temperature (provided that the amplifier is noiseless). The simplest inverting amplifier is a single transistor.Many amplifier IC's use the technique internally, including the VCA2611 and the AD8331. Actually I'm under impression that most low noise RF gain blocks use it internally.
: something I've never quite understood. Is it related to active : damping of mechanical systems?
Effectively the same thing.
This is the way to transform an amplifier into a refrigerator. Is there a generic way to transform a refrigerator into an amplifier? Both are devices which struggle to decrease entropy locally. Life does it, too.
Regards, Mikko