A
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- Jan 1, 1970
- 0
What kind of Penning trap system are you working on, Arch?
Carl,
We have an open cylindrical ICR cell.
Carl,
We have an open cylindrical ICR cell.
Carl,
We have an open cylindrical ICR cell.
Phil said:"Winfield Hill"
** The OP supplied a URL that *** REQUIRED ** payment to see the article.
He apologised for the blunder and made it available freely two hours ago.
Go shove your fuckwit opinions where the sun don't shine.
........ Phil
Carl Its an FTMS. The frequency of operation is 10 kHz to 1 MHz for the
amplifier. We have a 7 Tesla superconducting magnet.
thanks
the
amplifier. We have a 7 Tesla superconducting magnet.
thanks
My voltage noise data at Id=7mA for three input loads (only 10ohm is of
significance) can be glanced at http://www.24.fi/kiviranta/bf862_no3.gif
I was wondering this remark, too. It approaches the
un = sqrt( 8/3 k T / gm) figure quite nicely.
An interesting detail is the surprisingly high high-pass frequency,
which is due to the dc-blocking cap at the output. I tried the
ultra-high capacitance density ceramic from Murata, the 10uF GRM31
type. Did not expect much of it, but their impedance plot
http://www.24.fi/kiviranta/murata_grm31_z-theta.gif didn't look
too bad so gave one a try. It took some amount of detective work
and a hint from a colleaque before I noticed that their capacitance
value collapses when there is a dc biac voltage present across them.
http://www.24.fi/kiviranta/murata_grm31_biased.gif . Be warned!
Hello everyone,
I am a student who has been working on a low noise preamplifier for a
high impedance current source. I have put the model of the detection
circuit here:
http://img146.imageshack.us/img146/9748/detectmodelid8.jpg
Its a differential ac current source with an instrinsic capacitance ~
20pF on each side. I use 1M ohm resistors to bias my input JFETs.
The bandwidth i need is only from 10 Khz to couple of MHz.
In my learning process, i have realized few things such as selecting
JFETs as my input transistors for low leekage hence low input current
noise. Maximise the value of input resistor without disturbing the bias
of the input JFETs. However i still have couple of unanswered
questions:
1. How does the Cin of the JFETs effect the signal to noise. do i have
to match the input capacitance of the JFETs to the source capacitance
for minimum noise? How about if i put multiple JFETs in parallel to
reduce input voltage noise - do i have to revise my JFETs selection in
terms of input capacitance?
2. While evaluating the performance of the designed amplifier can i
neglect the equivalent input current noise, as i am using the JFETs?
3. Are there any good review articles or texts for low noise
preamplifier design (for capacitive sensors).
Please help!
thanks
-arch
current through your experiment? If that's the case, what is potential
value? It will be very hard to measure so low signal and have wide
bandwidth. I would suggest having a tuned circuit for frequencies of
interest and in addition, lockin amp after fet preamp. Reduced bandwidth
would help with noise problem.
Yes, i was suggested using JFETs and warm these up to 70 kelvin (justin sub pA range, although questionable if it would work on 4K. Could keep
them warm by heating PCB.
We did thought about it, if i can find a way to tune the preamplifierdifferent experiments or make it adjustable so you could tune it for
frequency of interest. In addition, you could match impedance of your amp to
experiment.