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The relationship between amplifier gain and temperature - RF Cafe
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Below are the old forum threads, including responses to the original posts.
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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
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.
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.
Unread postPosted: Fri May 27, 2005 3:57
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
Unread postPosted: Sat May 28, 2005 8:07 am
Your probably right,
I may be thinking of the current and not S21.