Post subject: The relationship between amplifier gain and
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.
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.