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A High-Performance Open Source Oscilloscope: development log & future ideas

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nctnico:
Just wondering... has any work been done on an analog front-end? I have done some work on this in the past; I can dig it up if there is interest. Looking at the Analog devices DSO fronted parts it seems that these make life a lot easier.

tom66:

--- Quote from: nctnico on November 17, 2020, 10:56:11 am ---Just wondering... has any work been done on an analog front-end? I have done some work on this in the past; I can dig it up if there is interest. Looking at the Analog devices DSO fronted parts it seems that these make life a lot easier.

--- End quote ---

I've got a concept and LTSpice simulation of the attenuator and pre-amp side, but nothing has been tested for real or laid out.  It would be useful to have an experienced analog engineer look at this - I know enough to be dangerous but that's about it.

At the time I was looking at a relay-based attenuator for the -40dB step and then a gain/attenuator block for +6dB to -38dB (think it was a TI part, I'll dig it out) which would get you from +6dB to -78dB attenuation.  Enough to cope with typical demands of a scope (1mV/div to 10V/div).

I was also looking into how to do 20MHz B/W limit and whether it would be practical to vary the varicap voltage with some PWM channels on an MCU to fine tune bandwidth limits.

tom66:
The existing AFE is purely ac-coupled.  Attached schematic.  The ADC needs about 1Vp-p input to get full scale code.

Presently the ADC diffpairs go over SATA cables, they are cheap and (usually) shielded.

Zucca:

--- Quote from: nctnico on November 16, 2020, 08:34:06 pm ---Personally I don't have a real need for high waveform update rates. Deep memory is usefull

--- End quote ---

Ditto. Normally on our benches we have already a high waveform rate scope.
I believe many of us have (or would buy) a USB/PC scope to cover application where deep memory is needed.

For a project like this I would put all my poker fiches to get as much memory as possible. All in.

Circlotron:

--- Quote from: tom66 on November 15, 2020, 02:16:28 pm ---Over the past year and a half I have been working on a little hobby project to develop a decent high performance oscilloscope, with the intention for this to be an open source project.  By 'decent' I class this as something that could compete with the likes of the lower-end digital phosphor/intensity graded scopes e.g. Rigol DS1000Z,  Siglent SDS1104X-E,  Keysight DSOX1000, and so on. <snip>  I'll welcome any suggestions.

--- End quote ---
Sounds reminiscent of a newsgroup posting by a certain fellow from Finland some years ago... Lets hope it becomes as big.  :-+

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