Triangular wave on ring oscilator

[Belrmar]

I recently got my first analog oscilloscope, so to start checking its integrity i built a ring oscillator, to my surprise the output from 2 of the 3  Schmitt trigger inverters are , instead of square waves , triangular, i am using only capacitors so might it be that the trigger output is getting loaded?but i am using the same capacitors so i dont know why i would have 1 of the triggers giving a propper square wave

any ideas ?

[Lee Leduc]

Please post a schematic. People can't help without seeing your circuit.

Thanks

[Belrmar]

on each of the outputs there is a capacitor to slow the process down

[Brumby]

How do you think the capacitors slow the process down?

Just look at one point and think about the voltage across one of the capacitors....

[Belrmar]

well the output circuitry of each inverter will have to charge up the capacitor before it triggers the next inverter input into going low... i guess, also without them the circuit is not precisely stable, it just outputs a bunch of noise or something too high freq for my oscilloscope

[Brumby]

You should show the actual schematic of the circuit you have wired up - not a generic image with additional wording.  A photo of the circuit would also do.  Playing 20 questions gets very old very quick - and still may not provide the information needed.

Offering answers without knowing precisely what you have wired up can cause a LOT of confusion.

[Wimberleytech]

- check your connections
- check the capacitor values...all the same?
- add two more stages (5 stage ring oscillator) and see if you get similar results.

What part are you using?  Should not matter but I am curious.
What is the supply voltage?
Is the supply voltage coming from a battery or a bench supply?
Is this assembled on a protoboard or soldered?
Are you using a 10x probe on your oscilloscope?
What is the oscilloscope you are using?

Take a picture of the waveform you see and post it.

These questions may not all be critical, but the first step in getting help is to tell us EVERYTHING!!

[Belrmar]

ook lets start, the oscilloscope is a promax od-416, i am using a 10x probe(oscilloscope does not have compensation for that but i can live with it) , the part number is cd40106BE, supply voltage is 12v from a linear regulator powered by a switching one.all the caps are 22nf. oscilloscope set 1uS and 2v per division (having on account the 10x)

images here: https://imgur.com/a/wEfyz6C

[Benta]

Of course they are triangular. You have a current source (the 40106 outputs hitting their current limit) charging 22 nF. What else would they be?

[Lee Leduc]

Here's an Appliation note using inverters in oscillator circuits.
https://www.fairchildsemi.com/application-notes/AN/AN-118.pdf

[Wimberleytech]

ook lets start, the oscilloscope is a promax od-416, i am using a 10x probe(oscilloscope does not have compensation for that but i can live with it) , the part number is cd40106BE, supply voltage is 12v from a linear regulator powered by a switching one.all the caps are 22nf. oscilloscope set 1uS and 2v per division (having on account the 10x)

images here: https://imgur.com/a/wEfyz6C

Great!

Your triangle waveform ramp rate is 6 volts per microsecond (deltaV/deltaT = 6e6)

I = C x deltaV/deltaT
I = 22e-9 x 6e6 = 132 mA    The 40106 cannot deliver that much current.

Therefore, I think your capacitor is not 22nF.

Please show us a picture of the capacitor markings (all three side by side).

Why are traces different???  Assuming the caps are all the same, consider this possibility.  If you removed the caps from a tape carrier (often they come this way), I have found that there is glue reside on the terminals.  This residue can insulate the wire and thus not make a connection.  Make sure the terminals of the caps are clean and making good contact.

[Belrmar]

Therefore, I think your capacitor is not 22nF.

agreed i made a bit of a fool of myself, the markings where 221 not 223, i should use my glasses more often

[Wimberleytech]

Therefore, I think your capacitor is not 22nF.

agreed i made a bit of a fool of myself, the markings where 221 not 223, i should use my glasses more often

Ahaaa!!  No problem.  I wear 3x readers and sometimes even that is not enough!!

Still does not answer why one of the outputs is a square wave.

[Belrmar]

Just used another of the ic's form my batch and this one is giving me 3 square waves.... i am a bit confused, might be some esd dmg that led to a damaged output stage? a bad puppy on the batch... no idea tbh

[Brumby]

With 3 caps on 3 stages, I would expect 3 triangular waveforms.  3 square waves doesn't make sense.  I would be really checking the contacts of those caps.

Is it still running at the same (or similar) frequency with 3 square waves?