The relationship between amplifier gain and temperature - RF Cafe Forums
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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
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.
Unread postPosted: 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 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.