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a basie FET question..

S

siliconmike

Jan 1, 1970
0
An FET (n channel enhancement mode type) can conduct bi-directionally
from drain to source as long as Vgs is of the order of +10 volts...

(am I right?)

and ... (more conditions?)

Mike
 
T

Tim Williams

Jan 1, 1970
0
Well, since the source and drain are indistiguishable on a garden-variety
JFET, figure it out.

And BTW... I doubt you should be playing with microprocessors, especially
those dealing with recharging explosive caustic cells (not necessarily
batteries!) if you don't know that a JFET gate has a diode characteristic
when forward biased. +10Vgs is rather impressive; how many JFETs did you
burn for that?

MOSFET on the other hand...

Tim
 
S

siliconmike

Jan 1, 1970
0
Tim said:
Well, since the source and drain are indistiguishable on a garden-variety
JFET, figure it out.

And BTW... I doubt you should be playing with microprocessors, especially
those dealing with recharging explosive caustic cells

Please don't assume such things.

(not necessarily
batteries!) if you don't know that a JFET gate has a diode characteristic
when forward biased. +10Vgs is rather impressive; how many JFETs did you
burn for that?

Hey, do you collect them ? ;)
MOSFET on the other hand...

Tim

+10Vgs - you should have guessed I'm talking about MOSFETs.

see this:
http://en.wikipedia.org/wiki/Top_posting
 
M

mc

Jan 1, 1970
0
And BTW... I doubt you should be playing with microprocessors, especially
those dealing with recharging explosive caustic cells (not necessarily
batteries!) if you don't know that a JFET gate has a diode characteristic
when forward biased. +10Vgs is rather impressive; how many JFETs did you
burn for that?

*Bzzzt!* He said "n channel enhancement mode type" which implies MOSFET.
 
F

Fred Bloggs

Jan 1, 1970
0
siliconmike said:
An FET (n channel enhancement mode type) can conduct bi-directionally
from drain to source as long as Vgs is of the order of +10 volts...

(am I right?)

and ... (more conditions?)

Mike

The N-FET will always conduct from source to drain through the body
diode regardless of Vgs.
 
C

Clifford Heath

Jan 1, 1970
0
Fred said:
The N-FET will always conduct from source to drain through the body
diode regardless of Vgs.

Though if I understand the 4 quadrant speed control tips from the
guy at 4qd.co.uk, when the FET is on, it'll conduct forward *or*
reverse currents with a Vds much less than a diode drop. Regen
braking is achieved by turning on both low-side NFETs of an H-bridge
until the short-circuit current through the motor L rises enough to
be usefully dumped back into the supply...?
 
J

John Larkin

Jan 1, 1970
0
An FET (n channel enhancement mode type) can conduct bi-directionally
from drain to source as long as Vgs is of the order of +10 volts...

(am I right?)

Yes.

and ... (more conditions?)

There's almost always a substrate diode from source to drain that will
turn on about -.6 volts anyhow.

John
 
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