Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: VDMOS_LDMOS_parameters[T] Posted: Thu Nov 03, 2005 5:41 pm
Joined: Thu Nov 03, 2005 5:34 pm
I need the papers about parameters the amplifiers with transistors VDMOS, LDMOS versus temperature.
Is bias control necessarily in amplifier with LDMOS ??
How is the large influence of temperature on parameters in amplifiers with transistors LDMOS ??
thanks for information
Post subject: Posted: Sat Nov 05, 2005 11:36 am
Joined: Mon Jun 27, 2005 2:02 pm
Hello again jarys,
Welcome to the magnificent world of RF Power Amplifiers!
LDMOS transistors are sensitive to temperature (As any other active device). When the temperature increases the Drain current Ids increases too and the output power level increases with it. So you should provide a negative feedback in order to reduce the drain current over temperature. This is done by using a thermistor in the Gate circuit. The thermistor is part of a voltage divider which reduces the Vgs voltage and by that reduces the Drain current.
Here is a link to a Freescale (Formerly motorola) which uses this scheme:
Should you need more information, please post and I will be keen to help you!