Bulk

[Spehro Pefhany]

Probably a dumb question here.. but.. what happens to the DC
characteristics of, say, a p-channel MOSFET if I pull the bulk
potential above the source by a few volts? Will Id vs. Vgs change
much?


Best regards,
Spehro Pefhany

 

[Jim Thompson]

Probably a dumb question here.. but.. what happens to the DC
characteristics of, say, a p-channel MOSFET if I pull the bulk
potential above the source by a few volts? Will Id vs. Vgs change
much?


Best regards,
Spehro Pefhany

Not a dumb question at all. It moves the channel around similar to
the gate, so transconductance and threshold change.

Do you have a specific type in mind? Does it have a model available?

Let me know. If you don't have a model I can run a generic device
and post the plots so you can see what it looks like.

...Jim Thompson

 

[Spehro Pefhany]

Not a dumb question at all. It moves the channel around similar to
the gate, so transconductance and threshold change.

Do you have a specific type in mind? Does it have a model available?

Let me know. If you don't have a model I can run a generic device
and post the plots so you can see what it looks like.

...Jim Thompson

That would be great.

These guys, which have common bulk:

http://www.aldinc.com/pdf/ALD1117.pdf
http://www.aldinc.com/pdf/ALD1116.pdf

I see a plot of changes vs. *substrate* bias but not bulk-- all the
specs are at Vbs = 0. These parts are nicely specified for analog
applications.

My idea is to use these as pass transistors for a number of
independent high precision 10uA current sources of both polarities.
Will current flow in or out of that pin? I was thinking to connect it
to a voltage 2.5V beyond the rail.

Best regards,
Spehro Pefhany

 

[Spehro Pefhany]

That would be great.

These guys, which have common bulk:

http://www.aldinc.com/pdf/ALD1117.pdf
http://www.aldinc.com/pdf/ALD1116.pdf

I see a plot of changes vs. *substrate* bias but not bulk-- all the
specs are at Vbs = 0. These parts are nicely specified for analog
applications.

My idea is to use these as pass transistors for a number of
independent high precision 10uA current sources of both polarities.
Will current flow in or out of that pin? I was thinking to connect it
to a voltage 2.5V beyond the rail.

^^^^^
oops, make that "source"
Best regards,
Spehro Pefhany

 

[Joerg]

That would be great.

These guys, which have common bulk:

http://www.aldinc.com/pdf/ALD1117.pdf
http://www.aldinc.com/pdf/ALD1116.pdf

I see a plot of changes vs. *substrate* bias but not bulk-- all the
specs are at Vbs = 0. These parts are nicely specified for analog
applications.

My idea is to use these as pass transistors for a number of
independent high precision 10uA current sources of both polarities.
Will current flow in or out of that pin? I was thinking to connect it
to a voltage 2.5V beyond the rail.

You might also look at the SD5400 datasheet. A decade ago I've used them
a lot for such stuff because the substrate was brought out on a separate
package pin. Then they became boutiqueish and expensive :-(

 

[Jim Thompson]

Probably a dumb question here.. but.. what happens to the DC
characteristics of, say, a p-channel MOSFET if I pull the bulk
potential above the source by a few volts? Will Id vs. Vgs change
much?


Best regards,
Spehro Pefhany

Here you go....

http://analog-innovations.com/SED/PMOS-Body-Test.pdf

...Jim Thompson

 

[Spehro Pefhany]

Here you go....

http://analog-innovations.com/SED/PMOS-Body-Test.pdf

...Jim Thompson

Thanks, Jim! Exactly what I need.

Best regards,
Spehro Pefhany

 

[Jim Thompson]

Thanks, Jim! Exactly what I need.

Best regards,
Spehro Pefhany

You're welcome!

When are you and "C" coming to Phoenix again?

...Jim Thompson