From: sleeper75se (sleeper75se_at_yahoo.se)
Date: 2002-01-10 08:16:11
Hi Jim, Joerg and all.
I've updated the input stage schematic a bit, so now it is more
flexible. New version is in the files-section.
Changes:
The shield driver is now optional - in a TL061 package on its own.
The biasing circuit is gone - I'm saving it for the ADC/digital board.
In-amp gain is now 112.3, which together with G = 23 forms a total
gain of 2583. That's as close to the optimal 2560 I can get with
standard values and minimal number of resistors. Should improve noise
figures too.
The AC coupling is still there, but you can now disable it by setting
jumpers or throwing a switch.
With both poles enabled, DC and delta amplitudes ranging from +/-30mV
(at 0.1Hz) and up (at lower frequencies) can be handled without
amplifier saturation. The price you pay is lower delta-range (< 1Hz)
amplification.
Power RC filter now sports 220 ohm resistors.
Input capacitors are now 10/100pF, but I'm still using 4.7K carbon
resistors, as recommended by Linear, when there are no FET-diodes.
The filter now has fc = 110Hz => possible to use lower sample rates.
In return the attenuation at higher frequencies (40-60Hz) is greater,
but max 10% (1dB) @ 60Hz.
/Andreas
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:36 BST