From: Jim Meissner (jpmeissner_at_mindspring.com)
Date: 2002-01-29 19:14:09
Dear Joerg:
The input stage I used has DC coupling and I noticed that when I had a 10 Kprotection resistor in series with the input to the op amp, the noise higher than when I shorted it out. I probably should have changed it to a 1 K,but I guess I was lazy and left the short.
So by inspecting the BrainMaster input stage, I guess at some low frequencythe source resistance will be 10 Meg as the Xc of the 0.01 mf capacitor increases with lower frequencies. I wonder if you could try to simulate thatstage again using larger capacitor values. I would be interested to see what capacitor value will give "good" noise down to 0.1 Hz? Somewhere I have the schematic for the original Mind Mirror. I think they used a 10 or 100 mf capacitors feeding into a discrete transistor for the lowest possible noise.
Juergen P. (Jim) Meissner
Check out my Website at www.MeissnerResearch.com
Read about the benefits of the Brain State Synchronizer sounds for improving your life and health.
----- Original Message -----
From: Joerg Hansmann
To: buildcheapeeg_at_yahoogroups.com
Sent: Monday, January 28, 2002 10:41 PM
Subject: Re: [buildcheapeeg] Brainmaster input stage
Hi Andreas,
----- Original Message -----
From: Andreas Robinson <sleeper75se_at_yahoo.se>
To: <buildcheapeeg_at_yahoogroups.com>
Sent: Monday, January 28, 2002 3:35 PM
Subject: [buildcheapeeg] Brainmaster input stage
> Ok, second try. The brainmaster input stage, slightly
> modified, attached as a text file.
What do you think about the AD620 input current noise
(especially at low frequencies) relating to the high-impedance
high-pass network C4,R4 and C5,R5 ?
I have used a similar (HP with asymmetric bias path) network
with INA114 and got disastrous results (many uV of low frequency
noise)
> > Component values:
> > R4: 10M 1% metal film
> > R5: 10M 1% metal film
...
> > C4: 0.01 uF 2% polypropylene
> > C5: 0.01 uF 2% polypropylene
...
Regards,
Joerg
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:37 BST