From: Jim Meissner (jpmeissner_at_mindspring.com)
Date: 2002-01-08 14:59:26
Dear Andreas:
My opinion is that the LT1167 is protected well enough and I would not do anything more at this time. If you look at figure 5 that is enough. The two 100 pf capacitors must go to a good ground. The 1.6 K resistors should not add much noise and will protect the amplifier from any condition that I can imagine. Let's get a prototype working first before we over design. As I said earlier, consider the preamp to be flexible. Put it in a separatebox that can easily be changed.
The opto isolator is what must be excellent to protect the patient. That is where the effort must be spent. Joerg says it is too simple to even worry about. If it is so simple lets see it.
I looked at your receiver design. My main concern is that the base of Q2 is left floating and leakage current and noise at higher temperatures may inadvertently turn Q2 on. A 10 k or so from base to emitter would prevent that. Has Joerg looked at this design? I would be interested in his opinion.
Juergen P. (Jim) Meissner
Check out my Website at www.MeissnerResearch.com
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----- Original Message -----
From: sleeper75se
To: buildcheapeeg_at_yahoogroups.com
Sent: Tuesday, January 08, 2002 8:29 AM
Subject: [buildcheapeeg] Re: Input protection
--- In buildcheapeeg_at_yahoogroups.com, "Jim Meissner" <jpmeissner_at_mindspring.com> wrote:
> Dear Andreas:
>
> > The cost is decent (ranging from $3.70 to $7.40), and from just
> > browsing through the datasheet, I think it is better. Also, it
> > comes with sufficient ESD protection built in. Just add two 5k
> > resistors! :-
>
> I think you found a great amplifier (LT1167) that solves the ESD
> problems. Also the 2N4393 FET diodes are probably much better than
> the 2N3904 that I suggested.
> Notice their RFI reduction comments!
Hi Jim,
Yes, it looks very nice! My modified schematic looks now like an
application note from Linear Technology. (Hmm, maybe they can sponsor
us. :-)
One question about those FET-diodes... they are only connected to V+.
Shouldn't there be diodes to V- as well? Of course, the people at
Linear know what they are doing...
/Andreas
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:36 BST