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Sci.Electronics.Basics -> quick emitter follower question
There are 25 messages in this thread.
You are currently looking at messages 20 to 25.
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Author: EeyoreDate: 13:19 15-09-06
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tempus fugit wrote:
> "Eeyore" <rabbitsfriendsandrelations@REMOVETHIS.hotmail.com> wrote
in
> > tempus fugit wrote:
> >
> > > > JFETs make very very acceptable audio switches when used correctly.
> > >
> > > I'm intrigued. Any suggestions on how to use one for this application?
> >
> > Dead easy.
> >
> > Use a nice low Ron jfet like a J108 and pull it off with a negative
> > voltage on the gate.
> > http://www.fairchildsemi.com/pf/J1/J108.html
> >
> > Use an open-collecter arrangement to drive the gate with say 10M from
> > gate to source. The signal path is from drain to source ( bidirectional ).
> Use a
> > 10k 'pull down' R on both in and out to avoid any DC levels getting into the
>
> > switch.
> >
> > If finding a negative voltage is a problem use a p-channel device like a
> > J174 and pull the gate positive.
> > http://www.fairchildsemi.com/pf/J1/J174.html
> >
> > The n-channel parts have lower Ron as do the lower numbered devices in
> > each family. The tradeoff is a higher Vgs to turn them off.
> >
>
> >Hi Ee
>
> I actually discovered the J105 and was thinking of trying to use it somehow
> already.
Yeah you could use that. Do note that it needs 10V to turn it off though.
> I haven't really worked with JFETs much before, and am only now becoming
> familiar with the open collector thing (which would be open drain in this
> case?).
No. The open collector arrangement is to drive the fet gate from a bipolar
transistor.
> Could we move this discussion to ABSE and I can post a schematic of
> what I think it should be set up like? I'm also unsure of the biasing
> required.
I'll crosspost it now.
Oh and please try to avoid top-posting, thanks.
Graham
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Author: tempus fugitDate: 21:11 15-09-06
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"Eeyore" <rabbitsfriendsandrelations@REMOVETHIS.hotmail.com> wrote in
message news:450AE0BF.8B622F79@REMOVETHIS.hotmail.com...
>
>
> tempus fugit wrote:
>
> > "Eeyore" <rabbitsfriendsandrelations@REMOVETHIS.hotmail.com>
wrote in
> > > tempus fugit wrote:
> > >
> > > > > JFETs make very very acceptable audio switches when used
correctly.
> > > >
> > > > I'm intrigued. Any suggestions on how to use one for this
application?
> > >
> > > Dead easy.
> > >
> > > Use a nice low Ron jfet like a J108 and pull it off with a negative
> > > voltage on the gate.
> > > http://www.fairchildsemi.com/pf/J1/J108.html
> > >
> > > Use an open-collecter arrangement to drive the gate with say 10M from
> > > gate to source. The signal path is from drain to source (
bidirectional ).
> > Use a
> > > 10k 'pull down' R on both in and out to avoid any DC levels getting
into the
> >
> > > switch.
> > >
> > > If finding a negative voltage is a problem use a p-channel device like
a
> > > J174 and pull the gate positive.
> > > http://www.fairchildsemi.com/pf/J1/J174.html
> > >
> > > The n-channel parts have lower Ron as do the lower numbered devices in
> > > each family. The tradeoff is a higher Vgs to turn them off.
> > >
> >
> > >Hi Ee
> >
> > I actually discovered the J105 and was thinking of trying to use it
somehow
> > already.
>
> Yeah you could use that. Do note that it needs 10V to turn it off though.
>
>
> > I haven't really worked with JFETs much before, and am only now becoming
> > familiar with the open collector thing (which would be open drain in
this
> > case?).
>
> No. The open collector arrangement is to drive the fet gate from a bipolar
> transistor.
>
>
> > Could we move this discussion to ABSE and I can post a schematic of
> > what I think it should be set up like? I'm also unsure of the biasing
> > required.
>
> I'll crosspost it now.
>
> Oh and please try to avoid top-posting, thanks.
>
> Graham
>
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Author: tempus fugitDate: 10:41 16-09-06
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OK.....
I've posted the schem a few times over the last 24 hrs or so, but it isn't
appearing here, so I don't know if it's appearing where you are. I wonder if
it is getting stripped or something.
Is anyone seeing my other posts with the schem?
Thanks
"Eeyore" <rabbitsfriendsandrelations@REMOVETHIS.hotmail.com> wrote in
message news:450AE0BF.8B622F79@REMOVETHIS.hotmail.com...
>
>
> tempus fugit wrote:
>
> > "Eeyore" <rabbitsfriendsandrelations@REMOVETHIS.hotmail.com>
wrote in
> > > tempus fugit wrote:
> > >
> > > > > JFETs make very very acceptable audio switches when used
correctly.
> > > >
> > > > I'm intrigued. Any suggestions on how to use one for this
application?
> > >
> > > Dead easy.
> > >
> > > Use a nice low Ron jfet like a J108 and pull it off with a negative
> > > voltage on the gate.
> > > http://www.fairchildsemi.com/pf/J1/J108.html
> > >
> > > Use an open-collecter arrangement to drive the gate with say 10M from
> > > gate to source. The signal path is from drain to source (
bidirectional ).
> > Use a
> > > 10k 'pull down' R on both in and out to avoid any DC levels getting
into the
> >
> > > switch.
> > >
> > > If finding a negative voltage is a problem use a p-channel device like
a
> > > J174 and pull the gate positive.
> > > http://www.fairchildsemi.com/pf/J1/J174.html
> > >
> > > The n-channel parts have lower Ron as do the lower numbered devices in
> > > each family. The tradeoff is a higher Vgs to turn them off.
> > >
> >
> > >Hi Ee
> >
> > I actually discovered the J105 and was thinking of trying to use it
somehow
> > already.
>
> Yeah you could use that. Do note that it needs 10V to turn it off though.
>
>
> > I haven't really worked with JFETs much before, and am only now becoming
> > familiar with the open collector thing (which would be open drain in
this
> > case?).
>
> No. The open collector arrangement is to drive the fet gate from a bipolar
> transistor.
>
>
> > Could we move this discussion to ABSE and I can post a schematic of
> > what I think it should be set up like? I'm also unsure of the biasing
> > required.
>
> I'll crosspost it now.
>
> Oh and please try to avoid top-posting, thanks.
>
> Graham
>
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Author: John WoodgateDate: 10:57 16-09-06
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In message <40f87$450c0ccb$d1d89bd0$31884@PRIMUS.CA>, dated Sat, 16 Sep
2006, tempus fugit <toccata@no.spam.ciaccess.com> writes
>I've posted the schem a few times over the last 24 hrs or so, but it
>isn't appearing here, so I don't know if it's appearing where you are.
>I wonder if it is getting stripped or something.
Post it ONLY to ABSE. It will be stripped if you post to SEB as well.
>
>Is anyone seeing my other posts with the schem?
No.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
There are benefits from being irrational - just ask the square root of 2.
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
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Author: Kevin AylwardDate: 04:09 17-09-06
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Contact | Electronic Portal
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