Author Topic: Finding JFET output admittance from datasheet  (Read 766 times)

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Offline aneevuserTopic starter

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Finding JFET output admittance from datasheet
« on: January 22, 2020, 03:51:32 pm »
I want to find  \$r_{ds}/y_{os}\$ for a JFET (specifically a J105) but it's not quoted in the datasheet (not in this one at least: http://www.farnell.com/datasheets/2304100.pdf?_ga=2.16164336.77463200.1579706202-1922662769.1578909818).

OTOH, the datasheet does provide a graph of \$I_D\$ vs \$V_{DS}\$ from which I can estimate it. Is this a sensible way to get the value, or am I missing a simpler/more accurate approach?
 

Offline rfeecs

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Re: Finding JFET output admittance from datasheet
« Reply #1 on: January 22, 2020, 07:27:47 pm »
Maybe look at figure 7 (Output conductance vs Drain Current)?

Alternately search for J105 SPICE model.  Output conductance can be calculated at a specific operating point.  Or you can simulate it with SPICE.
 
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Offline aneevuserTopic starter

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Re: Finding JFET output admittance from datasheet
« Reply #2 on: January 22, 2020, 10:10:41 pm »
Maybe look at figure 7 (Output conductance vs Drain Current)?

Right, thanks. I hadn't noticed that. Unpleasantly logarithmic (and small) though, so may be tricky to get an accurate value from it.
 


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