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Old 6th Dec 2017, 12:19 am   #3
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 1,281
Default Re: 'Kalmus' wideband RFPA: info.?

At work we have quite a few of the classic AR (Amplifier Research) range of amplifiers that are very similar to this type of amplifier. These tend to cover a couple of decades of bandwidth and are typically a big and rugged (and very heavy!) class A amplifier.

If this amplifier is of a similar type then I would not expect it to have ALC. ALC generally isn't desirable in a big general purpose class A amplifier like this. I think some of the amplifiers in the AR amplifier range are run in class AB and these tend to have inferior linearity but are presumably cheaper and probably weigh a lot less. I'm not sure if the class AB versions will have ALC but I doubt it. There will probably be some form of overload cutout or limiter but not any form of classic ALC. But there will probably be exceptions to this.

These amplifiers generally require about 0dBm to +5dBm drive level so they often have a gain in the region of 45dB. Because these amplifiers are meant to be used as a general purpose (class A) lab amp for research purposes, I'd expect the small signal gain to be quite flat across the whole range. Maybe +/-2dB maximum variation in gain? A key selling point of these amplifiers is the instantaneous bandwidth and the flat gain. So they would be good when used for wideband pulsed/swept applications.
It's probably worth finding out if your amplifier is meant to run in class A or class AB. Also, try and spot any feedback circuits that would be there to help control the gain response. Maybe the gain response isn't as flat for the class AB versions but I'd expect all of these amplifiers to use feedback to provide controlled input and output impedance and flat gain across the full range.
Regards, Jeremy G0HZU

Last edited by G0HZU_JMR; 6th Dec 2017 at 12:37 am.
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