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What is the lowest possible value that Vgs(th) can be for any BSS123 FET?

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treez

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The BSS123 FET is said to have a VGS(TH) of 0.8 to 2V in page 2 of the datasheet (below)
But Fig 4 (page 3) shows that vgs(th) never goes down to 0.8v, no matter how high the temperature.
…So, do we have to assume that fig 4 is just the “average” case, and that another graph like fig 4 exists, but at every temperature the vgs(th) voltage being 0.8V less?

BSS123 FET datasheet
**broken link removed**
 

Well, page 2 is for 1 mA drain current at 25 Deg C and fig 4 is for 250 uA drain current at the specified temperatures in the graph.
 

thanks, yes I noticed that, but still don't know what is the lowest that vgs(th) could be say at 170degc ambient.....could it be as low as 0.5v in a worst case tolerance batch?
 

I do not think we are given enough information to know that.
 

thanks, i am inclined to agree, I wonder is there a mV/degC figure for V(gs)th with temperature for fets.......?
 

Adding the typical Vgs,th temperature coefficient shown in Fig. 4 to the 25 °C Vgs,th range of 0.8 to 2 V sounds reasonable, but strictly spoken, there's no specification of worst case Vgs,th over the full temperature range in the datasheet.
 

This is one of those instances where you would have to:
1- Contact the manufacturer.

2- Determine the information experimentally.
 
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thanks, we're stuffed though because our qty's are way too small for us to be worth them helping, and we don't have an environmental chamber that we can take up to 170degC ambient.
 

we don't have an environmental chamber that we can take up to 170degC ambient.
Click to expand...
Do you plan to finish design based on theoretical considerations only? Make the first real tests at the customers site?
 
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    Vbase

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FvM said:
Do you plan to finish design based on theoretical considerations only? Make the first real tests at the customers site?
Click to expand...

This is a normal procedure in Britain, I thought you knew that. :)
 

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