High current switching
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Posts: 46,084
I'd like to use the BS2 to switch high current 10 to 20 amps per
output. I've been researching FET's and found a 2SK2232 on
digikey.com. The spec sheet say's it has a 4volt gate drive. Does
this mean the stamps 5volt outputs would switch this FET. Any advise
appreciated.
output. I've been researching FET's and found a 2SK2232 on
digikey.com. The spec sheet say's it has a 4volt gate drive. Does
this mean the stamps 5volt outputs would switch this FET. Any advise
appreciated.
Comments
I'm working on something similar myself right now..using
logic-level (5V gate) N-channel Mosfets to switch 12V .5A load.
As far as I understand, as long as you keep the device within
in/output specs, they interface directly with only a current limit
resistor between stamp and gate lead. I am currently researching the
highest value that I can use for these "buffer" resistors. The gate
voltage, not current triggers the device so they should work with
quite large resistors. The other thing to look at is the Rds(on) value
(resistance from drain-source when conducting) and use it to figure
power dissipated by the device (you might need some hella-big heat sink.)
In short, yeah-they work.
Regards
C.C.
--- In basicstamps@yahoogroups.com, "voltsguy" <brianr@d...> wrote:
> I'd like to use the BS2 to switch high current 10 to 20 amps per
> output. I've been researching FET's and found a 2SK2232 on
> digikey.com. The spec sheet say's it has a 4volt gate drive. Does
> this mean the stamps 5volt outputs would switch this FET. Any advise
> appreciated.
If you drive a mosfet with PWM, for exemple, you will need a current due to the
capacity of the gate.
So it is better to lower the driving resistor as much as possible.
Regards
ECO
Original Message
From: "captainconstructor" <captainconstructor@y...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, September 08, 2003 6:25 AM
Subject: [noparse][[/noparse]basicstamps] Re: High current switching
> Brian,
> I'm working on something similar myself right now..using
> logic-level (5V gate) N-channel Mosfets to switch 12V .5A load.
> As far as I understand, as long as you keep the device within
> in/output specs, they interface directly with only a current limit
> resistor between stamp and gate lead. I am currently researching the
> highest value that I can use for these "buffer" resistors. The gate
> voltage, not current triggers the device so they should work with
> quite large resistors. The other thing to look at is the Rds(on) value
> (resistance from drain-source when conducting) and use it to figure
> power dissipated by the device (you might need some hella-big heat sink.)
> In short, yeah-they work.
> Regards
> C.C.
>
>
> --- In basicstamps@yahoogroups.com, "voltsguy" <brianr@d...> wrote:
> > I'd like to use the BS2 to switch high current 10 to 20 amps per
> > output. I've been researching FET's and found a 2SK2232 on
> > digikey.com. The spec sheet say's it has a 4volt gate drive. Does
> > this mean the stamps 5volt outputs would switch this FET. Any advise
> > appreciated.
>
>
> To UNSUBSCRIBE, just send mail to:
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of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
>
The switching speed depends in the amount of energy (Q) vs time
applied to the Gate (Gate-Source capacitance).
A large Stamp to Gate resistor will slow down the switching times
(turn-on and turn-off).
The MOSFET dissipates large amounts of power during the transition.
If the switching load is inductive, you will have a bunch of DEAD
MOSFETS in your hands.
That is why there are specially designed MOSFET drivers.
READ device specs very carefully.
The stamp output, I suspect, is a TTL equivalent output, and though it
may state it's 5 Volts out, it may not be fully 5.0 Volts. A pull up
resistor on the output of the stamp would help. Someone step in here
and holler if I'm wrong on this.
However, the stamp should be able to turn the fet on I would suspect.
Looks like a good choice, but there are caveats<G>.
Things to consider, what is the switch on time. If the fet will be on a
long time, you need a very low on resistance. Some fets we have used
have 0.025 Ohm on resistance, others have 1-2 Ohms of on resistance.
Looking at the data sheet, the 2SK2232 has 0.036 Ohm resistance if the
drive is 10 Volts. However, at 4 Volts, the on resistance is specified
to be 0.057, but may be as high as 0.08. So at 20 Amps, under absolute
worse conditions, you will have 1.6 Volts drop across the FET. Is this
Voltage loss going to affect your circuit? Also, if the fet is on 100%
of the time, you will be dissipating 32 Watts in the FET.
Also looking at the data sheet, while it will operate full on at 4
Volts, it works better at 10 Volts. Again, your actual circuit needs
may not cuase this to be a problem.
A long dissertation where only a short answer was needed, but things
like this have caused my fingers to become blistered in the past<G>.
All the best
Original Message
From: voltsguy [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=StI0IiotCGtzwQMLhSW0JBkOx2EzVmt6Jij2fsw020LOF7-y8NfVtbJi1AepSdRe_5dHLq0eiRF8BQ]brianr@d...[/url
Sent: Sunday, September 07, 2003 8:58 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] High current switching
I'd like to use the BS2 to switch high current 10 to 20 amps per
output. I've been researching FET's and found a 2SK2232 on
digikey.com. The spec sheet say's it has a 4volt gate drive. Does
this mean the stamps 5volt outputs would switch this FET. Any advise
appreciated.
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject
and Body of the message will be ignored.
Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
Does this come into play for slow switching apps (250mS or slower)?
My concerns are mostly about the higher drain voltage (+12V) leaking
to the gate or gate current rising too high. I have 9 such outputs ( 8
within the HIGH pins) on a BS2e.
Oh, and Voltsguy, you listening? I forgot one important detail that
you may not know. That 4V gate drive voltage is usually 4V above the
Source pin voltage( for an N-Channel device)..So if your source pin is
at the stamp's ground potential it'll work..
if source pin V > +2V or so you will need to boost the gate drive
voltage. Er. Right ECO? :-)
No Message
C.C.
--- In basicstamps@yahoogroups.com, "ECO" <ecourt@b...> wrote:
> Statically you are right, but dynamically not.
> If you drive a mosfet with PWM, for exemple, you will need a current
due to the capacity of the gate.
> So it is better to lower the driving resistor as much as possible.
> Regards
> ECO
>
>
Original Message
> From: "captainconstructor" <captainconstructor@y...>
> To: <basicstamps@yahoogroups.com>
> Sent: Monday, September 08, 2003 6:25 AM
> Subject: [noparse][[/noparse]basicstamps] Re: High current switching
>
>
> > Brian,
> > I'm working on something similar myself right now..using
> > logic-level (5V gate) N-channel Mosfets to switch 12V .5A load.
> > As far as I understand, as long as you keep the device within
> > in/output specs, they interface directly with only a current limit
> > resistor between stamp and gate lead. I am currently researching the
> > highest value that I can use for these "buffer" resistors. The gate
> > voltage, not current triggers the device so they should work with
> > quite large resistors. The other thing to look at is the Rds(on) value
> > (resistance from drain-source when conducting) and use it to figure
> > power dissipated by the device (you might need some hella-big heat
sink.)
> > In short, yeah-they work.
> > Regards
> > C.C.
> >
> >
> > --- In basicstamps@yahoogroups.com, "voltsguy" <brianr@d...> wrote:
> > > I'd like to use the BS2 to switch high current 10 to 20 amps per
> > > output. I've been researching FET's and found a 2SK2232 on
> > > digikey.com. The spec sheet say's it has a 4volt gate drive. Does
> > > this mean the stamps 5volt outputs would switch this FET. Any
advise
> > > appreciated.
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the
Subject and Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> >
> >
> >
> >
MOSFETS go to www.irf.com.
For operation and application of MOSFETS Drivers, go to MAXIM and
look for MOSFETS Drivers (TSC429 and MAX4429 families).
(logic level driven).
I'm given to understand that the value of the current limiting
resistor is selected to limit current to safe levels for the
Stamp's I/O pin in the event of a shorted FET.
Bypassing the current limiting resistor with a 0.047uF ceramic allows
the FET to turn on fairly quickly by passing the leading edge of the
turn on signal to the FET and probably assists in draining the charge
of the FET gate at the signals end.
I've also discovered that the addition of a gate bleed resistor
assists in the FET's rapid turn off provided that this voltage divider
still enables sufficient voltage at the gate for the current load
intended.
A 4.9V/5.1V Zener from gate to ground should insure that in the event
the I/O pin is in input mode, no damaging voltages can creep through
to the Stamp in the event of FET shorts.
--- In basicstamps@yahoogroups.com, "voltsguy" <brianr@d...> wrote:
> I'd like to use the BS2 to switch high current 10 to 20 amps per
> output. I've been researching FET's and found a 2SK2232 on
> digikey.com. The spec sheet say's it has a 4volt gate drive. Does
> this mean the stamps 5volt outputs would switch this FET. Any advise
> appreciated.
switching.
I did it, in a simple application, by boosting the voltage and current ouput
from the stamp with a transistor.
Drain to load to +12V
Collector to 470ohms to +12V, Collector also to Gate
Base to 470ohms to Stamp pin
GND to Emitter , GND also to Source
The Load is ON when the Stamp pin in high.
Regards
ECO
Original Message
From: "captainconstructor" <captainconstructor@y...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, September 09, 2003 2:42 AM
Subject: [noparse][[/noparse]basicstamps] Re: High current switching
> ECO,
> Does this come into play for slow switching apps (250mS or slower)?
>
> My concerns are mostly about the higher drain voltage (+12V) leaking
> to the gate or gate current rising too high. I have 9 such outputs ( 8
> within the HIGH pins) on a BS2e.
>
>
> Oh, and Voltsguy, you listening? I forgot one important detail that
> you may not know. That 4V gate drive voltage is usually 4V above the
> Source pin voltage( for an N-Channel device)..So if your source pin is
> at the stamp's ground potential it'll work..
> if source pin V > +2V or so you will need to boost the gate drive
> voltage. Er. Right ECO? :-)
>
> No Message
> C.C.
>
>
>
> --- In basicstamps@yahoogroups.com, "ECO" <ecourt@b...> wrote:
> > Statically you are right, but dynamically not.
> > If you drive a mosfet with PWM, for exemple, you will need a current
> due to the capacity of the gate.
> > So it is better to lower the driving resistor as much as possible.
> > Regards
> > ECO
> >
> >
Original Message
> > From: "captainconstructor" <captainconstructor@y...>
> > To: <basicstamps@yahoogroups.com>
> > Sent: Monday, September 08, 2003 6:25 AM
> > Subject: [noparse][[/noparse]basicstamps] Re: High current switching
> >
> >
> > > Brian,
> > > I'm working on something similar myself right now..using
> > > logic-level (5V gate) N-channel Mosfets to switch 12V .5A load.
> > > As far as I understand, as long as you keep the device within
> > > in/output specs, they interface directly with only a current limit
> > > resistor between stamp and gate lead. I am currently researching the
> > > highest value that I can use for these "buffer" resistors. The gate
> > > voltage, not current triggers the device so they should work with
> > > quite large resistors. The other thing to look at is the Rds(on) value
> > > (resistance from drain-source when conducting) and use it to figure
> > > power dissipated by the device (you might need some hella-big heat
> sink.)
> > > In short, yeah-they work.
> > > Regards
> > > C.C.
> > >
> > >
> > > --- In basicstamps@yahoogroups.com, "voltsguy" <brianr@d...> wrote:
> > > > I'd like to use the BS2 to switch high current 10 to 20 amps per
> > > > output. I've been researching FET's and found a 2SK2232 on
> > > > digikey.com. The spec sheet say's it has a 4volt gate drive. Does
> > > > this mean the stamps 5volt outputs would switch this FET. Any
> advise
> > > > appreciated.
> > >
> > >
> > > To UNSUBSCRIBE, just send mail to:
> > > basicstamps-unsubscribe@yahoogroups.com
> > > from the same email address that you subscribed. Text in the
> Subject and Body of the message will be ignored.
> > >
> > >
> > > Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
> > >
> > >
> > >
> > >
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
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of the message will be ignored.
>
>
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>
>
>
>
The Load is ON when the Stamp pin is LOW
Original Message
From: "ECO" <ecourt@b...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, September 09, 2003 10:09 AM
Subject: Re: [noparse][[/noparse]basicstamps] Re: High current switching
> As said by another member, you allways have interest in an as fast as possible
switching.
> I did it, in a simple application, by boosting the voltage and current ouput
from the stamp with a transistor.
>
> Drain to load to +12V
> Collector to 470ohms to +12V, Collector also to Gate
> Base to 470ohms to Stamp pin
> GND to Emitter , GND also to Source
>
> The Load is ON when the Stamp pin in high.
> Regards
> ECO
>
Original Message
> From: "captainconstructor" <captainconstructor@y...>
> To: <basicstamps@yahoogroups.com>
> Sent: Tuesday, September 09, 2003 2:42 AM
> Subject: [noparse][[/noparse]basicstamps] Re: High current switching
>
>
> > ECO,
> > Does this come into play for slow switching apps (250mS or slower)?
> >
> > My concerns are mostly about the higher drain voltage (+12V) leaking
> > to the gate or gate current rising too high. I have 9 such outputs ( 8
> > within the HIGH pins) on a BS2e.
> >
> >
> > Oh, and Voltsguy, you listening? I forgot one important detail that
> > you may not know. That 4V gate drive voltage is usually 4V above the
> > Source pin voltage( for an N-Channel device)..So if your source pin is
> > at the stamp's ground potential it'll work..
> > if source pin V > +2V or so you will need to boost the gate drive
> > voltage. Er. Right ECO? :-)
> >
> > No Message
> > C.C.
> >
> >
> >
> > --- In basicstamps@yahoogroups.com, "ECO" <ecourt@b...> wrote:
> > > Statically you are right, but dynamically not.
> > > If you drive a mosfet with PWM, for exemple, you will need a current
> > due to the capacity of the gate.
> > > So it is better to lower the driving resistor as much as possible.
> > > Regards
> > > ECO
> > >
> > >
Original Message
> > > From: "captainconstructor" <captainconstructor@y...>
> > > To: <basicstamps@yahoogroups.com>
> > > Sent: Monday, September 08, 2003 6:25 AM
> > > Subject: [noparse][[/noparse]basicstamps] Re: High current switching
> > >
> > >
> > > > Brian,
> > > > I'm working on something similar myself right now..using
> > > > logic-level (5V gate) N-channel Mosfets to switch 12V .5A load.
> > > > As far as I understand, as long as you keep the device within
> > > > in/output specs, they interface directly with only a current limit
> > > > resistor between stamp and gate lead. I am currently researching the
> > > > highest value that I can use for these "buffer" resistors. The gate
> > > > voltage, not current triggers the device so they should work with
> > > > quite large resistors. The other thing to look at is the Rds(on) value
> > > > (resistance from drain-source when conducting) and use it to figure
> > > > power dissipated by the device (you might need some hella-big heat
> > sink.)
> > > > In short, yeah-they work.
> > > > Regards
> > > > C.C.
> > > >
> > > >
> > > > --- In basicstamps@yahoogroups.com, "voltsguy" <brianr@d...> wrote:
> > > > > I'd like to use the BS2 to switch high current 10 to 20 amps per
> > > > > output. I've been researching FET's and found a 2SK2232 on
> > > > > digikey.com. The spec sheet say's it has a 4volt gate drive. Does
> > > > > this mean the stamps 5volt outputs would switch this FET. Any
> > advise
> > > > > appreciated.
> > > >
> > > >
> > > > To UNSUBSCRIBE, just send mail to:
> > > > basicstamps-unsubscribe@yahoogroups.com
> > > > from the same email address that you subscribed. Text in the
> > Subject and Body of the message will be ignored.
> > > >
> > > >
> > > > Your use of Yahoo! Groups is subject to
> > http://docs.yahoo.com/info/terms/
> > > >
> > > >
> > > >
> > > >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
> >
> >
> >
> >
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
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of the message will be ignored.
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>
>
>
>
cause extremely high dissipation issues with the fet, as it will be in
the linear region for quite some time. Also, when in the linear region,
oscillation can be a problem.
Original Message
From: captainconstructor [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=-40-vlkR3fPGRHOZ_JwdpNTD8To_kIRFGNfQyGHZI58f-n_fNhWVNRi0PVpbJ5yVMrHj7fYnjd7ogU1U6QVnrKTgPZs]captainconstructor@y...[/url
Sent: Monday, September 08, 2003 8:42 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: High current switching
ECO,
Does this come into play for slow switching apps (250mS or slower)?
My concerns are mostly about the higher drain voltage (+12V) leaking to
the gate or gate current rising too high. I have 9 such outputs ( 8
within the HIGH pins) on a BS2e.
Oh, and Voltsguy, you listening? I forgot one important detail that you
may not know. That 4V gate drive voltage is usually 4V above the Source
pin voltage( for an N-Channel device)..So if your source pin is at the
stamp's ground potential it'll work.. if source pin V > +2V or so you
will need to boost the gate drive voltage. Er. Right ECO? :-)
No Message
C.C.
--- In basicstamps@yahoogroups.com, "ECO" <ecourt@b...> wrote:
> Statically you are right, but dynamically not.
> If you drive a mosfet with PWM, for exemple, you will need a current
due to the capacity of the gate.
> So it is better to lower the driving resistor as much as possible.
> Regards ECO
>
>
Original Message
> From: "captainconstructor" <captainconstructor@y...>
> To: <basicstamps@yahoogroups.com>
> Sent: Monday, September 08, 2003 6:25 AM
> Subject: [noparse][[/noparse]basicstamps] Re: High current switching
>
>
> > Brian,
> > I'm working on something similar myself right now..using
> > logic-level (5V gate) N-channel Mosfets to switch 12V .5A load.
> > As far as I understand, as long as you keep the device within
> > in/output specs, they interface directly with only a current limit
> > resistor between stamp and gate lead. I am currently researching the
> > highest value that I can use for these "buffer" resistors. The gate
> > voltage, not current triggers the device so they should work with
> > quite large resistors. The other thing to look at is the Rds(on)
> > value (resistance from drain-source when conducting) and use it to
> > figure power dissipated by the device (you might need some hella-big
> > heat
sink.)
> > In short, yeah-they work.
> > Regards
> > C.C.
> >
> >
> > --- In basicstamps@yahoogroups.com, "voltsguy" <brianr@d...> wrote:
> > > I'd like to use the BS2 to switch high current 10 to 20 amps per
> > > output. I've been researching FET's and found a 2SK2232 on
> > > digikey.com. The spec sheet say's it has a 4volt gate drive. Does
> > > this mean the stamps 5volt outputs would switch this FET. Any
advise
> > > appreciated.
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the
Subject and Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> >
> >
> >
> >
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject
and Body of the message will be ignored.
Your use of Yahoo! Groups is subject to
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are OK.
What is not OK is not to turn-off the MOSFET really fast if you are
switching a inductive load.
If you look with a scope the VDS and Id at the same time, you will
see a lot of power dissipated (Vds X Id) during the turn-off
That looks promising, thx ECO
Regards
C.C.
> As said by another member, you allways have interest in an as fast
as possible switching.
> I did it, in a simple application, by boosting the voltage and
current ouput from the stamp with a transistor.
>
> Drain to load to +12V
> Collector to 470ohms to +12V, Collector also to Gate
> Base to 470ohms to Stamp pin
> GND to Emitter , GND also to Source
>
> The Load is ON when the Stamp pin in high.
> Regards
> ECO
>
Original Message
> From: "captainconstructor" <captainconstructor@y...>
> To: <basicstamps@yahoogroups.com>
> Sent: Tuesday, September 09, 2003 2:42 AM
> Subject: [noparse][[/noparse]basicstamps] Re: High current switching
>
>
> > ECO,
> > Does this come into play for slow switching apps (250mS or
slower)?
> >
> > My concerns are mostly about the higher drain voltage (+12V)
leaking
> > to the gate or gate current rising too high. I have 9 such
outputs ( 8
> > within the HIGH pins) on a BS2e.
> >
> >
> > Oh, and Voltsguy, you listening? I forgot one important detail
that
> > you may not know. That 4V gate drive voltage is usually 4V above
the
> > Source pin voltage( for an N-Channel device)..So if your source
pin is
> > at the stamp's ground potential it'll work..
> > if source pin V > +2V or so you will need to boost the gate drive
> > voltage. Er. Right ECO? :-)
> >
> > No Message
> > C.C.
> >
> >
> >
> > --- In basicstamps@yahoogroups.com, "ECO" <ecourt@b...> wrote:
> > > Statically you are right, but dynamically not.
> > > If you drive a mosfet with PWM, for exemple, you will need a
current
> > due to the capacity of the gate.
> > > So it is better to lower the driving resistor as much as
possible.
> > > Regards
> > > ECO
> > >
> > >
Original Message
> > > From: "captainconstructor" <captainconstructor@y...>
> > > To: <basicstamps@yahoogroups.com>
> > > Sent: Monday, September 08, 2003 6:25 AM
> > > Subject: [noparse][[/noparse]basicstamps] Re: High current switching
> > >
> > >
> > > > Brian,
> > > > I'm working on something similar myself right now..using
> > > > logic-level (5V gate) N-channel Mosfets to switch 12V .5A
load.
> > > > As far as I understand, as long as you keep the device
within
> > > > in/output specs, they interface directly with only a current
limit
> > > > resistor between stamp and gate lead. I am currently
researching the
> > > > highest value that I can use for these "buffer" resistors. The
gate
> > > > voltage, not current triggers the device so they should work
with
> > > > quite large resistors. The other thing to look at is the
Rds(on) value
> > > > (resistance from drain-source when conducting) and use it to
figure
> > > > power dissipated by the device (you might need some hella-big
heat
> > sink.)
> > > > In short, yeah-they work.
> > > > Regards
> > > > C.C.
> > > >
> > > >
> > > > --- In basicstamps@yahoogroups.com, "voltsguy" <brianr@d...>
wrote:
> > > > > I'd like to use the BS2 to switch high current 10 to 20 amps
per
> > > > > output. I've been researching FET's and found a 2SK2232 on
> > > > > digikey.com. The spec sheet say's it has a 4volt gate drive.
Does
> > > > > this mean the stamps 5volt outputs would switch this FET.
Any
> > advise
> > > > > appreciated.
> > > >
> > > >
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