| Electronics > Projects, Designs, and Technical Stuff |
| DIY oscilloscope (yet again) |
| << < (9/9) |
| David Hess:
--- Quote from: gf on November 24, 2019, 09:27:08 am --- --- Quote from: David Hess on November 24, 2019, 02:34:16 am ---Part of it is the result of software upgradable bandwidth which means the hardware is designed for a higher than necessary bandwidth resulting in higher device noise. --- End quote --- (Unnecessary) bandwidth is certainly a significant contributor. On my JyeTech DSO 112a toy scope (~50 bucks, ~1-2MHz bandwidth), I can clearly see ~1.2mV quantization steps in the output of a DDS generator. But on my 1GSPS Hantek 6074BD, these steps drown in noise... --- End quote --- If it was just caused by the greater bandwidth, then the bandwidth limiting filter would remove it. Most of the noise comes from the FET used for the impedance converter at the front end. (1) All other things being equal, higher frequency parts have higher noise and higher flicker noise so designing a wider bandwidth front end and then limiting the bandwidth results in higher noise than if the front end was lower bandwidth to start with. (1) Unless integrated CMOS preamplifiers are used. Those things have incredibly high noise; like above 1000nV/SqrtHz at low frequencies. |
| Navigation |
| Message Index |
| Previous page |