Dr Ronald Stiffler SEC technology

[AlienGrey]

I used a 74C14 which is not fast enough for 18 MHz . I might have some 74AC14 chips somewhere, which have a much faster risetime (otoo 10 ns) which may allow operation at higher frequencies. Pain in butt to change the chip though because of the way I mounted it. Oh well.

Thought I would try it with a 16 or 20 Mhz to see where it fell over but no it still works and a 27mhz surely not but no it still works, TI for you
with an 8v line  well well well 3 oil holes in the ground, that is fast

[TinselKoala]

Come on AG, your measurements are NOT VALID if your signal exceeds the screen vertically! You are likely overloading your input preamps and you are clipping an unknown amount of data above and below what the screen shows.

To get a valid risetime measurement the scope has to see the FULL vertical span of the signal IN THE SCREEN DISPLAY. Otherwise how can it determine the 10%-90% points to measure the risetime?

But OK, you are oscillating at some high frequency. Do the tops and bottoms of your pulses look flat without ringing or over/undershoot? Impossible to tell due to your scope abuse.


But anyhow your point is well taken. If you want to use the SCO with an output buffer, don't use the 74C14 unless you are also using low (below 5MHz) frequencies.

[AlienGrey]

No 27mhz is pushing it a bit it's more like a sign wave on pin 10.  this pic is 1.68Mhz (1.687500mhz) out of pin 7 Q4
If they have done this to a 4060 i would like to see what they have done to a 4046 !

[Lidmotor]

All--- I tried that simple crystal oscillator circuit out with a 13.56 MHz crystal and it was pretty spectacular.  I ran it on a 9v battery and changed the 1K feed resistor to a 1000uH choke.  Here is the video of it:

https://www.youtube.com/watch?v=PqsVQPLXi3E

--Lidmotor

[TinselKoala]

I changed the 74C04 for a 74AC04 and that speeded it up considerably. Fast enough transitions now to cause considerable overshoot and ringing. I pulled the ground clip off the scope probe and used the little spring thing for ground instead and that cut down a lot of the ringing on the trace. (High Frequency scopologists take note.)
But of course now I'm limited to 5.5 V input, in contrast to the "C" version.