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be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
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Below are all of the forum threads, including all
the responses to the original posts.
Post subject: The relationship between amplifier gain and temperature
Unread postPosted: Tue May
24, 2005 10:00 pm
What is the relationship between amplifier gain and temperature?
Unread postPosted: Thu May 26, 2005 3:40 am
Joined: Tue Mar 15, 2005 11:43 pm
At typical case, amplifier gain will be decreased as temperature increased. It's related to transistor
parameters changes over temperature. Therefore, at large difference gain over temperature, the thermistor design
is necessary at DC bias line to compensate the changes caused by temperature difference.
hope it helps.
Unread postPosted: Thu May
26, 2005 1:57 pm
I agree with Jean. Another point you have to consider is that as the
temperature increases the amplifier's output power capability (P1dB) degrades as well as its linearity. The exact
opposite happens in lower temperatures.
Fri May 27, 2005 10:35 am
Cant remeber which it is, but BJTs and FETS behave differently over temperature.
I think ( not sure) the BJT gain will increase at higher temperature since the number of electrons injected in to
the base will increase. FETs will decrease at higher temperature since it is a voltage controlled device and the
channel resistance goes up at high temperatures.
postPosted: Fri May 27, 2005 3:57 pm
Don't mix between DC Gain and RF Gain. for example in BJT's the beta
will increase with temperature, where the S21 will decrease with temperature.
Unread postPosted: Sat May 28, 2005 8:07 am
Your probably right, I may be thinking of the
current and not S21.