Actually, with 50 ohms on both ends, there's no penalty for putting an LC bandpass before a MMIC. That would reduce nonlinearity overload possibilities.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
sign. I have a 5mV 8MHz signal I need to feed into an ADC, I want to do 2 things, filter it, and amplify it, the end result needs to fit on a fairly small pcb... something like 2" x 2" , I'm using FilterPro right now to come up with some filter ideas... do you think it's ok to do an active filer th at can do the gain and bandpass? Then feed that into an ADC... I'm looking at using an AD9238 (12-bit, 65MSPS) ADC... any tips/thoughts is greatly app reciated!
tting lost in noise that is around the same frequency of interest, it's com ing off a coax cable, 50ohm source
,, it would be great if I could get a couple stages with G=10
gh frequency noise? I've never used a CFB amp, I'll check them out
using a diff-amp to bring in my signal (similar to the order Larkin describ ed) diff-amp then filter then ADC driver?
before, but put one together and ran it in LTSpice, and it looks pretty go od, would just an LC bandpass filter work for this kind of thing?
n LC filter like this?
inOAMkNuZnZQalNEVWc
e reading back data from a sensor and was having to average a bunch of samp les to see his signal, seemed like an interesting problem so I've decided t o take a crack at it, and learn something along the way
thanks! I think after chasing various solutions, and struggling with simula ting active gain/filter stages at this frequency, I'm liking the passive LC route, also looking into that MMIC
would an LC filter with a discrete transistor gain stage of been better tha n opamps?
The best noise performance would result from an optimized matching/filtering network and some discrete fet, but the MMIC would sure be easy. Looks like a 3dB NF MMIC would be great with your 8 mv signal, with a bit of filtering on the output side to kill out-of-band noise.
These Darlington MMICS are cheap and simple and stable and they just always work. AC coupled of course. We've used them in pulse applications too, with a little cheating on bias. The ERA series is good too.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
gn. I have a 5mV 8MHz signal I need to feed into an ADC,
reading back data from a sensor and was having to average a bunch of sample s to see his signal, seemed like an interesting problem so I've decided to take a crack at it, and learn something along the way
That shows a sequence of bursts, maybe half dozen cycles each. The most appropriate filter for such things is a wavelet transform, and if you can 'add' the sig nals, it means that the times are synchronized somehow (which means you can constrain to a limited number of degrees of freedom, which is good).
I suspect a combination of summing and maybe autocorrelating (another kind of summing, that adds burst #N to burst #N + M) can get you amplitudes, phases, and rep eat times. Which If any of those are the useful data, it's hard to say, but clean signals mi ght be extracted without too much use of creativity or wishful thinking.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.