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jarys
Post subject: VDMOS_LDMOS_parameters[T] Posted: Thu Nov 03, 2005 5:41 pm

Lieutenant

Joined: Thu Nov 03, 2005 5:34 pm
Posts: 2
Location: POLAND
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


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IR
Post subject: Posted: Sat Nov 05, 2005 11:36 am

Site Admin


Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
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:

www.freescale.com/files/rf_if/doc/data_sheet/MRF372.pdf

Should you need more information, please post and I will be keen to help you!

_________________
Best regards,

- IR



Posted  11/12/2012
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