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| (pre-)amplifier to measure power supply noise |
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| exe:
Thank you very much, guys! I'll take suggestion into account and try to measure something. --- Quote from: imo on April 07, 2019, 06:30:17 am ---Mind the "bandwidth" of an opamp is always a product of the closed loop Gain and the BW. --- End quote --- Good point, I had doubts about that as well. I started to look into the datasheet and it says "[two-stage architecture] This architecture results in a 3.5 MHz bandwidth at a gain of 2000 for an equivalent gain bandwidth product of 7 GHz.". I'm glad they are explicit about that :) |
| exe:
--- Quote from: imo on April 07, 2019, 06:30:17 am ---FYI - below is a 2 transistors Amplifier with 72.4dB (4190x) gain, with 135kHz bandwith (30Hz-135kHz). I bet with good noise params for your application. --- End quote --- Nice old-school! May be I'll start with that, before buying expensive AD devices :). |
| not1xor1:
--- Quote from: exe on April 07, 2019, 08:53:40 pm --- --- Quote from: imo on April 07, 2019, 06:30:17 am ---FYI - below is a 2 transistors Amplifier with 72.4dB (4190x) gain, with 135kHz bandwith (30Hz-135kHz). I bet with good noise params for your application. --- End quote --- Nice old-school! May be I'll start with that, before buying expensive AD devices :). --- End quote --- That is a bad choice. Those AD ICs are differential amplifiers. They would take care and get rid of all common mode noise while that simple 2 BJTs amplifier will show just EMI noise in your lab. Look at "How to measure PSU noise and ripple" video and thread for more details. |
| Gerhard_dk4xp:
Quite a strong allegation. Show me a baseline at -190 dBV with your differential amplifier. The EMI noise in my lab must be something different. < https://www.flickr.com/photos/137684711@N07/24354944411/in/album-72157662535945536/ > noise density of some LEDs, 0 dB = 1 nV/rtHz, no cross correlation. regards, Gerhard |
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