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gmv
- Jan 1, 1970
- 0
Hello,
A couple questions regarding a relatively simple
home built op amp circuit. I am having a terrible
problem with noise.
All stages are simple RC single order butterworth filters.
The stages are as follows:
0. 50 feet of cable between the 450ohm coil sensor and the amplifier
1. Unity Gain Buffer Amp
2. Unity Gain High Pass Filter FL=160 seconds
3. 28.6dbv Low Pass Filter for Equalization FH=6 seconds
4. 21.7dbv Low pass Filter FH=2.4 Hz
5. 21.7dbv Low Pass Filter FH=2.4 Hz
6. 14.9dbv Low Pass Filter FH=2.4 Hz
7. Unity Gain High Pass Filter FL=160 Seconds Output into 5kohms.
The gains are not even simply because I
have been playing with those and are totally
open for changes. But the frequencies or periods are
solidly locked into place simply because that
is what I need.
The gain can be 83dbv to 90dbv overall.
Using a DC gain of 87dbv in a frequency range
of 100seconds to 1Hz and am having a terrible
problem with noise from sources other than
the desired signal. The op amps used are all OP177G.
[Question #1]
I. Is it important for the + and - inputs
to be resistively balanced to a high
precision & accuracy ?
[Question #2]
II. Major Noise sources seem to be RF, Hot/Cold, Electrostatic
in nature. What is the best way to guard against
all of these things ?
Right now everything is breadboarded and I do
not want to hard wire everything until I can beat
this noise problem.
I would post a diagram but since this site
does not allow binaries...oh well.
GMV
A couple questions regarding a relatively simple
home built op amp circuit. I am having a terrible
problem with noise.
All stages are simple RC single order butterworth filters.
The stages are as follows:
0. 50 feet of cable between the 450ohm coil sensor and the amplifier
1. Unity Gain Buffer Amp
2. Unity Gain High Pass Filter FL=160 seconds
3. 28.6dbv Low Pass Filter for Equalization FH=6 seconds
4. 21.7dbv Low pass Filter FH=2.4 Hz
5. 21.7dbv Low Pass Filter FH=2.4 Hz
6. 14.9dbv Low Pass Filter FH=2.4 Hz
7. Unity Gain High Pass Filter FL=160 Seconds Output into 5kohms.
The gains are not even simply because I
have been playing with those and are totally
open for changes. But the frequencies or periods are
solidly locked into place simply because that
is what I need.
The gain can be 83dbv to 90dbv overall.
Using a DC gain of 87dbv in a frequency range
of 100seconds to 1Hz and am having a terrible
problem with noise from sources other than
the desired signal. The op amps used are all OP177G.
[Question #1]
I. Is it important for the + and - inputs
to be resistively balanced to a high
precision & accuracy ?
[Question #2]
II. Major Noise sources seem to be RF, Hot/Cold, Electrostatic
in nature. What is the best way to guard against
all of these things ?
Right now everything is breadboarded and I do
not want to hard wire everything until I can beat
this noise problem.
I would post a diagram but since this site
does not allow binaries...oh well.
GMV