Equivalent Time Repetitive Signals and High Frequencies

[PixieDust]

I was watching this video:



thanks w2aew, you have a top quality channel, appreciate your hard work, have learned a great deal from you.

Basically, if you have a 20Mhz scope, you might not see higher frequency ringing that in a low frequency circuit might not even be expected.

My experiment is very niche in nature. I have a 100Mhz scope with 300Mhz equivalent time functionality for repetitive signals. I'm not sure how common this option is these days, I've never seen it on anything other than my scope but I haven't looked very hard so I don't know how useful it is to how many of you but it's going to be my little contribution.

Anyway, It's going to be especially interesting because the signal is repetitive but not nicely, it's not a sinusoid. It's also interesting because the ringing in that circuit is at 200Mhz, higher than my 100Mhz but lower than 300Mhz, so to my uneducated self (I'm an electronics beginner), this all sounds like an interesting experiment. I'm also in the process going to learn how my scope behaves.

What I need are two things.

1.) What voltage to use? and should it be DC or AC, I'm guessing DC.

2.) What transistor to use?

w2aew doesn't specify these things unfortunately.

I plan on buying the components and putting this thing together in a breadboard just like w2aew and then I'll upload a video with the results.

[David Hess]

1.) What voltage to use? and should it be DC or AC, I'm guessing DC.

Use DC coupling if the duty cycle varies.  Otherwise as the average voltage changes, then the baseline will wander up and down.

2.) What transistor to use?

Any 300 MHz small signal transistor like a 2N3904, 2N4401, or 2N2222 will work.

I plan on buying the components and putting this thing together in a breadboard just like w2aew and then I'll upload a video with the results.

In my experience equivalent time sampling DSOs displayed the spurious oscillation just fine *if* the amplitude was high enough.  The problem I have had in the past is that any DSO could not resolve the detail necessary to even see a low level spurious oscillation while an analog oscilloscope showed it as a noticable trace thickening.

[PixieDust]

Use DC coupling if the duty cycle varies.  Otherwise as the average voltage changes, then the baseline will wander up and down.

What would be an appropriate voltage? 9V?

In my experience equivalent time sampling DSOs displayed the spurious oscillation just fine *if* the amplitude was high enough.  The problem I have had in the past is that any DSO could not resolve the detail necessary to even see a low level spurious oscillation while an analog oscilloscope showed it as a noticable trace thickening.

Gocha, I have an analog scope, so I'm hoping to see a similar waveform to w2aew.

[David Hess]

Use DC coupling if the duty cycle varies.  Otherwise as the average voltage changes, then the baseline will wander up and down.

What would be an appropriate voltage? 9V?

Do you mean what would be an appropriate voltage for the phase shift oscillator w2aew demonstrates?  12 or 15 volts would be typical but 5 or 9 volts is feasible as well.

[PixieDust]

Yep exactly, don't know what voltage to apply to w2aew's circuit.