Best quadratic Mosfets and fets

Jmmlc · 5th October 2005, 06:31 PM

Hello,

I am requiring your advice about references for Fets and Mosfets having the best parabolic law relation (quadratic law) between Id and Vgs for Id values between 0 and 200mA.

Such very quadratic Fets and Mosfets are used in square law converter or square root converter. Others are used in wattmeters. Do you know of any references.

Did someone knows abouit quadraticity studies for Fets and Mosfets.

Best regards from Paris (France)

Jean-Michel Le Cléac'h

darkfenriz · 5th October 2005, 08:54 PM

I think you need very low power mosfets, maybe IRFD series with low Id max, because at low currents the curve is rather exponential and getting closer to quadratic at reasonable fraction of Id max, say 1/4..

ilimzn · 5th October 2005, 11:09 PM

IRFDs can be misleading, they are relatively low power dissipation, but use the same cells as regular IRF parts, just smaller numbers. Idmax is still quite high for them (1A). Perhaps something like BS107? Maybe even some of the RF MOSFETs (BF9xx), depletion mode may put the Id vs Vgs point at a low enough current...

Jmmlc · 6th October 2005, 12:13 PM

Hello,

Thanks for the replies.

I'll study the quadraticity of those Mosfets.

Best regards from Paris (France)

Jean-Michel Le Cléac'h

5th October 2005, 06:31 PM	#1
Jmmlc diyAudio Member Join Date: Oct 2005	Best quadratic Mosfets and fets Hello, I am requiring your advice about references for Fets and Mosfets having the best parabolic law relation (quadratic law) between Id and Vgs for Id values between 0 and 200mA. Such very quadratic Fets and Mosfets are used in square law converter or square root converter. Others are used in wattmeters. Do you know of any references. Did someone knows abouit quadraticity studies for Fets and Mosfets. Best regards from Paris (France) Jean-Michel Le Cléac'h

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5th October 2005, 08:54 PM	#2
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	I think you need very low power mosfets, maybe IRFD series with low Id max, because at low currents the curve is rather exponential and getting closer to quadratic at reasonable fraction of Id max, say 1/4..

5th October 2005, 11:09 PM	#3
ilimzn diyAudio Member Join Date: Feb 2005 Location: Zagreb	IRFDs can be misleading, they are relatively low power dissipation, but use the same cells as regular IRF parts, just smaller numbers. Idmax is still quite high for them (1A). Perhaps something like BS107? Maybe even some of the RF MOSFETs (BF9xx), depletion mode may put the Id vs Vgs point at a low enough current...

6th October 2005, 12:13 PM	#4
Jmmlc diyAudio Member Join Date: Oct 2005	Hello, Thanks for the replies. I'll study the quadraticity of those Mosfets. Best regards from Paris (France) Jean-Michel Le Cléac'h

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