I found that on my scope a 470Ω resistor eliminates much of the ringing as attached.

Your scope and probe are at the edge of their capabilities. The 5th harmonic will be attenuated by 6dB so you'll never be able to see a 10MHz square wave.

 

Your scope and probe are at the edge of their capabilities. The 5th harmonic will be attenuated by 6dB so you'll never be able to see a 10MHz square wave.

The TBS1052B is a 50 MHZ scope. Not sure what you mean.

 

The TBS1052B is a 50 MHZ scope. Not sure what you mean.

A 10MHz square wave is made up of a sine wave at 10MHz, 30MHz, 50MHz, ... To see a square wave, the scope needs to have the bandwidth for 3+ harmonics. You will always see rounded edges on a 10MHz square wave because your scope and probe don't have sufficient bandwidth.

If your scope and probe weren't designed to be a "system", each will be 3db down at 50MHz. As I mentioned, I found that Tektronix specifies bandwidth for the overall system when you're using a probe intended to be used with a particular scope. In that case, attenuation is only 3dB at the rated system bandwidth.

 

Re the output voltage,
My guess is its a 3v3 ttl output module,
as far as the output is concerned, provided its TTL compatible, the module is compliant,

Re the shape,
that's your termination, or lack there of.

Its not really there, its just how you are measuring and your termination.
Buffering will give you the same result.

 

The TBS1052B is a 50 MHZ scope. Not sure what you mean.

square wave is made out of the odd harmonics,
Typically to see a good square wave, you need at least the 5th harmonic, preferable out to 11th.

https://en.wikipedia.org/wiki/Square_wave

 

square wave is made out of the odd harmonics,
Typically to see a good square wave, you need at least the 5th harmonic, preferable out to 11th.

https://en.wikipedia.org/wiki/Square_wave

Thanks Andrew

 

Why has no one mentioned this.
The use of breadboard for high frequency circuits is just not recommended. the capacitance between the "tracks" is staggeringly high and at the frequencies you are using makes a large different to the performance of your circuit.
Try strip board for at least the higher frequency part. Or the old favorite of the dead bug technique.
I think most of your problems will go away
Then you need to transfer this to a well designed PCB

 

Why has no one mentioned this.
The use of breadboard for high frequency circuits is just not recommended. the capacitance between the "tracks" is staggeringly high and at the frequencies you are using makes a large different to the performance of your circuit.
Try strip board for at least the higher frequency part. Or the old favorite of the dead bug technique.
I think most of your problems will go away
Then you need to transfer this to a well designed PCB

mentioned many times in the post, i.e post #4. et all.

 

hI,
Please note the TS has been Banned from the AAC site.
E

 

Why has no one mentioned this.
The use of breadboard for high frequency circuits is just not recommended. the capacitance between the "tracks" is staggeringly high and at the frequencies you are using makes a large different to the performance of your circuit.

Stray capacitance isn't that staggeringly high and the portion of the OP's circuit that operates at 10MHz is localized. After the first divider, it's down to 1MHz and parasitic effects will be an order of magnitude lower.

 

I did a test with the circuit I breadboarded. The nodes that would have the most parasitic capacitance would be between the input and output of the inverter, so I put a 22pF cap in parallel with the feedback resistor. Extra capacitance from the input to ground wasn't relevant. The phase shift cap is sometimes larger; I used 22pF because it was handy.

There was no significant effect. Doubling the capacitance from the input to ground also had no significant effect.