| Products > Test Equipment |
| Best 14-Bit Digital Oscilloscope |
| << < (4/7) > >> |
| nctnico:
My recommendation would be to look for something with differential inputs. A pre-amplifier can also be an option to bypass noise in a cheaper oscilloscope front-end. |
| edavid:
--- Quote from: trentender on October 13, 2023, 02:14:26 pm ---Need both wideband (100MHz minimum) and low noise sensitivity (20uV) and lowish cost.Not asking much I know!!!!!! --- End quote --- This is actually impossible. Referring to a handy noise calculator: https://www.daycounter.com/Calculators/Thermal-Noise-Calculator.phtml If you plug in 25C, 50ohms, and 100MHz, you get thermal noise of 9uV RMS (about 60uV P-P). So it's impossible to build a (non-cryogenic) 100MHz oscilloscope with only 20uV P-P (broadband) noise. |
| G0HZU:
If you just want to look at sinewaves then you don't need lots of instantaneous bandwidth. For example, here's a 20uV pkpk signal at 70MHz being fed to my ancient (500MHz BW) 8 bit HP DSO. To be able to measure it and trigger on it, I've used a precision (2 stage) LNA followed by a 70MHz bandpass filter that is about 10MHz wide. I haven't factored in the loss of the BPF so it shows 18uV pkpk instead of 20uV pkpk, but you get the idea... The other plots show the flat gain response of the first stage of the preamp. The input VSWR is very low and the noise figure is less than 3dB. I normally use this precision preamp for noise figure testing, but it can also be used with an oscilloscope to look at tiny RF signals. You can see that the gain response is very flat at 32dB across a huge bandwidth. |
| thm_w:
--- Quote from: edavid on October 13, 2023, 06:47:28 pm ---This is actually impossible. Referring to a handy noise calculator: https://www.daycounter.com/Calculators/Thermal-Noise-Calculator.phtml If you plug in 25C, 50ohms, and 100MHz, you get thermal noise of 9uV RMS. So it's impossible to build a 100MHz oscilloscope with 20uV P-P noise. --- End quote --- |
| mawyatt:
More like 77K, not 25C :-+ Best, |
| Navigation |
| Message Index |
| Next page |
| Previous page |