diyAudio

diyAudio (http://www.diyaudio.com/forums/)
-   Solid State (http://www.diyaudio.com/forums/solid-state/)
-   -   Thermal compensation for BJT drivers with Lateral FET output (http://www.diyaudio.com/forums/solid-state/198528-thermal-compensation-bjt-drivers-lateral-fet-output.html)

Neutrality 14th October 2011 05:53 PM

Thermal compensation for BJT drivers with Lateral FET output
 
Do you need any thermal compensation for the drivers in an output stage with Lateral FETs?

Since the Laterals are thermally stable with just a resistor or resistor+pot in the vbe multiplier, thermal compensation for the BJT drivers should not be needed.

From what I can see from other designs with Lat FET output stages and BJT drivers, no thermal compensation seems to be needed.

mlloyd1 14th October 2011 06:03 PM

the original Hitachi data sheets & app notes (as well as old Hafler construction manuals) recommended 100mA per device quiescent current puts you pretty close to the zero tempco point for the lateral MOSFETs. If you do the same, you likely woon't need any fancy tempco circuitry.

Bensen 14th October 2011 06:56 PM

My 2 cents,

I would not place the drivers on the main heatsink, this to avoid big temperature changes for the drivers.
I you place the drivers on a smaller heatsink and set the OPS bias after that the driver heatsinks reached a stable temperature, it should be fine. That's my experience.

Greetz

Neutrality 14th October 2011 07:13 PM

Quote:

Originally Posted by mlloyd1 (Post 2745819)
the original Hitachi data sheets & app notes (as well as old Hafler construction manuals) recommended 100mA per device quiescent current puts you pretty close to the zero tempco point for the lateral MOSFETs. If you do the same, you likely woon't need any fancy tempco circuitry.

Was talking about the BJT drivers needing thermal compensation, not the Lateral FETs.

Neutrality 14th October 2011 07:14 PM

Quote:

Originally Posted by Bensen (Post 2745872)
My 2 cents,

I would not place the drivers on the main heatsink, this to avoid big temperature changes for the drivers.
I you place the drivers on a smaller heatsink and set the OPS bias after that the driver heatsinks reached a stable temperature, it should be fine. That's my experience.

Greetz

That is good to know and more or less what I expected.

Michael Chua 14th October 2011 07:21 PM

Quote:

Originally Posted by Neutrality (Post 2745811)
Do you need any thermal compensation for the drivers in an output stage with Lateral FETs?

Since the Laterals are thermally stable with just a resistor or resistor+pot in the vbe multiplier, thermal compensation for the BJT drivers should not be needed.

From what I can see from other designs with Lat FET output stages and BJT drivers, no thermal compensation seems to be needed.

Yes, BJT drivers don't need any thermal compensation.


All times are GMT. The time now is 06:22 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio


Content Relevant URLs by vBSEO 3.3.2