#231 

Alan Wolke, you are amazing person! ... Iam now 45yo ... but watching your videos is fulfilling my dreams about electronics from my childhood. Finally I found your lectures!

I love the style of your videos - it's almost a cliché, but it really is like having a great teacher sit next to you and explain stuff. Thank you.

Very nice! Your "Circuit Fun" videos always live up to their name. :)

Bravo! In all the time I've been following YT, I've only found two such excellent educators. You and DiodeGoneWild.

Nice circuit analysis Alan. Thanks for your time to build it on breadboard...

Great little tutorial on this interesting circuit. It's a very visual circuit on the scope as well; so that makes it more educational to visualize what is happening. Thanks for all your great vids.

Thanks so much. It's my new years resolution to build and describe 20 circuits. I may give the stairstep generator a shot!

I will give that a go ! This has got to be one of those few times when i wanted a circuit that does more with simple parts and better than i could of expected ...all the links very very helpful thank you !

Such an amazing circuit.. ties in a lot of concepts together.. great for learning

This video is still relevant in oct '23. I found some regular opamps in one of my bins, so I ordered the required r2r opamps and I will be building this circuit soon, just for fun and education.

The way you explain these circuits is engaging even for a novice like me. Using the scope as a demonsration is icing on the cake. Thanks!

This was just plain fun. Well done as always. Thanks a lot Alan.

Beautiful circuit, and crystalclear explanation. Thanks for sharing!

Beautifully explained as usual. Love the analog stuff

Very interesting as usual and a little over my head at times - lol Well presented valuable training. Thank you for providing it and Keep up the great work!

Always nice to Watch and have the schematic besides. Many could learn from the way you do.

Thank you for providing the schematic. I'm going to print it out and put it on my wall.

This is a great reason to get the breadboard out...cheers

Great video. This works really well with swapping out the 555s and op amp with 15ms trigger clocks for CV generation for electronic music gear.

If the school teachers are as motivated and interesting as you are, we would have an army of young radio/electronics enthusiasts. Well done Alan! Good on ya mate!!!

Very clearly explained as usual- I am playing with a similar stair-step circuit for use as an analog frequency divider

My new favorite YT channel. This is amazing!!! Thank you so much for taking the time! 73 N0BPS

Again a great lesson..happy and healthy 2020

A very great explanation - perfect job!

Oh.... that's what the RESET pin is for! Still learning. Great video as always and thanks for the education!

thanks - I have to add one of these to the system I am currently designing and this video really made the analysis simple

Really awesome circuit analysis! Thanks.

Allen thanks for doing these videos, great job

Very interesting circuit, and Great Video. Thanks for sharing.

As always ... Great job. Wonderfull explanation. Thank you.

Nice lesson as always Alan! It will be interesting to see what I can do with it controlling the reset pin with resistance rather than voltage.

جزاك الله خيرا وزادك علما والله اكبر

What a refreshing video, to see an oscillator in this day and age that's not some super integrated proprietary PLL kind of deal or a microcontroller running one line of code is just very pleasant.

Impatient to try this but waiting for rail to rail op amps to arrive...tried LM324. Got the relaxation oscillator running and adjusted pulse timings. Then the 555 pulse generator and added the reset. More adjustment to get about 12 steps between resets. Then added the pulse integrator but results were not as expected. Reset was not taking the integrator capacitor to ground. Eventually figured out that the 8k2 base resistor needed to be reduced to turn on a 2N3904 sufficiently to get down to ground during a reset. Guess this is a consequence of not using a rail to rail op amp. More adjustment of the base drive and finally an output close to yours. Not quite as square steps but close. Spent a few hours working on this circuit because it looked fascinating and have learnt lots about basic electronics. There is no substitute for doing - great that your videos are, there is even more to be gained by building and modifying. Been great fun and learning.

Great video content as usual. Thank you.

Amazing explanation!

Awesome video Alan. thanks for posting

Thanks for easy to understand review, as usual :-)

Hi Alan, It reminds me of the basis of a transistor curse tracer on an oscilloscope of the 70's, when at school. It could be a "fun circuit" to see you build :-). Your videos are greatly instructive. Thank you for share so much knowledge with us. Regards, RJM.

What a master piece!!

very very interesting circuit. thank you

Wow, this is amazing - got to go build one!

A little something for the first oscillator is you can use a linear pot and 2 diodes in the feedback network so you can have a near constant frequency ( roughly, you will have to vary C to get different frequencies) but where the duty cycle is variable over a very wide range, from around 5% to 95% as you turn the knob. Can be used with the whole circuit to sample the output to get a specific step using a differentiator driving a sample gate ( 4066 switch). But I can see a use for an analogue staircase generator where you can select the number of steps easily just by using RC delays.

Nice video once again! Fun circuit, clear explanation, as usuaL, Thanks! I see many potential uses, gives me ideas!.

simply beautiful.

Love this! Please do more videos like this if you can!

Thank you! Your videos always inspire me to experiment with LTspice. I made one with transistors only containing just a single oscillator. Works in LTspice, but I don't know if it works in real life. :D

*Vielen Dank* für Deine wunderbaren Videos!

Your schematics are very neat !

As always great! Awesome! Thanks a lot!

Neat circuit! BTW that output stage is called a Deboo integrator, one of an interesting class based on Howland current sources. It's great for single-supply as it's non-inverting, unlike conventional Miller integrators.

very informative and very interesting video. I like your channel.

Thank you, it's very interesting video. I wanna watch your videos on analog circuits from basic to the one more complicated.

I like your excellent explanations.....well done...!!!!

Very nice little circuit. If you put about a 47K resistor on the base of Q2/Q1 to ground, it'll work better with 2N2222 transistors - they tend not to turn off very fast and hold the 555 in reset too long so you only get 4 or 5 steps out of it. Just a thought :) Love your videos.

Still a great watch!

This reminds me of a AGC circuit I stumbled into building on breadboard about 30 years ago... The accumulator drove attenuators, a detector drove the accumulator, and a timer reset it to detector level after the hang time. Fast attack, no pumping, fixed hang time; for something so crude it worked great. Sadly I've long lost the schematic I drew.

Seems like a 556'd be a good fit too :) fun stuff

Another enjoyable video. Thank you! Would it be possible to ramp down instead of up? or even more daring, ramp both up and down like a triangle wave?

the reseting op amp may be another 555 timer .. I have too much ot this buggers and that would i do.. Everyone can adapt the circuit with his own view .. The final op am is neat ! Great job

Thanks for your awesome training techniques they are very clear and understanding. Have you ever experience any three phase circuits to parallel AC generators, or do you have any ideas on what chip should be use for phasing sequence two or more AC generators

Like you voice over circuit analyzing technique.

That's very look like a kind of flip-flop circuit! Very awesome how you do without memory circuit or microcontroller! THK!

Very cool!

So cool!!

I really do enjoy your circuit analysis videos. Are there future plans for this circuit? - A video linearity tester? - A transistor curve tracer?

Ooo, I like this a lot! Simple components and design is sexy! I wonder how it sounds...

I use a LM358 as OPAM ( i have no "rail to rail" one) and I need to put a diode between 8k2 resistor and transistor bases in orden to achive transistors off state. So I get a nice stairstep.

Really nice video. IMHO had the right amount of content and some nicely paced descriptions. Just the right level for me. I was wondering... does it need an output buffer... any load will disrupt the stairstep? Also, it's a nice old school design but isn't it actually cheaper nowadays to use a small pin-count controller?

Does the output stage need to be as complex? Could we just have a diode from 555 output -> capacitor positive side then put a buffer/voltage-follower there?

Your tektronix mdo4104c oscilloscope - where would be a good place to find such a scope? I have seen some for $17k to $23 which is too high for a hobbyist like my self. Could you recommend a similar but less expensive scope?

Hi nice video as always hopefully to view lesson about rgb analog ttl digital lvds signals and conversions. thanks

As always great explanation. I'm assuming this circuit must have a lower frequency boundary? on the basis that the step will decay and there will be a point where the sag makes this too nonlinear, is this right?

Hi Alan, As always,your content and presentation skills are absolutely impeccable !! Hope I did not miss it,but could you clarify why you have the 6k8 resistor to ground on the output of U1. TIA.

Probably a stupid question here, but as a newbie, can I use my op amp oscillator in place of the 555? If so what modifications would you need to make? I have limited access to materials at the moment.

I thing you can automate it by letting the relaxation oscillator making the high frequency pwm and let the 555 in monoflop configuration which gets triggered by a high at out to make the discharging step at the output.

Hi, After time domain, let's go to frequency domain.. So could you make a video about making a "frequency staistep" for a spectrum analyzer ? Thank's ! May be Mr Carlson's could do this too.. Who will be the first to challenge this ?

There is a bar on top of the reset pin on the diagram, which means it is an active low reset, which means the reset is default high. When there is a low, the circuit resets. But your scope is showing an active high reset - whenever the pulse is high, it resets.

Youre great and your final output stairstep* wave/signal is worth goldif it is possible to make this work in the 400V-1200V range, it is because the wave form is exactly right for a Quasi continues wave tesla coil!! So my question is how to amplify it even more? * :)

How can you predict that both Q1 and Q2 will turn on having the bases in parallel and a single resistor? Extremely well matched?

You are a great teacher! I'm curious: what applications would you use a staircase generator or signal? I seem to recall part of the old NTSC color TV signal having one?

In general, how do you come up with the resistors value?

I got it going but got some extra lines. Is 50mhz Rigol scope fast enough?? On another note I held a match to the DUT and watched the curves rise and fall, that was cool.

Could the circuit at 2:19 be modified to produce PWM signal by replacing those 2 timing resistors with a pot?

Would be nice to see this circuit actually doing something

Can it be used for making an analog to digital converter? For example, you compare the analog input voltage with the height of the stairstep and then output a digital signal when the analog input equals the stairstep's height.

Did you used to make synthesyzers?

Reminds me of the old days of CRTs...

So if you make the 555 pulses wider, that means more time to increase the capacitor voltage so the steps would have a bigger voltage difference between?

Hi I like these kind of videos just wondring if i can give you a veroboard ver that i have done for this circuit To help others that might want to make this. I have had fun making this on veroboard over the weekend. Thanks for reading

I have a Heathkit IG-1275 Log/Lin Sweep Generator. I would like to display markers, say 10 marks both Log and Linear, across the X axis on an Oscilloscope using the scopes Z axis input to show the marks. Is this possible to display marks both linear and logarithmic across the X axis using the Sweep Gate Output, Sweep Output, or Analog Output of the IG-1275 using the Step Generator circuit #231?

Will this work with two 741's? All I have laying around. How important are the resistor values for the non inverting input of the reset oscillator? I substituted 10k for voltage divider and 4.7k and 2.2k for the others. I got this circuit constructed but something isn't right.. Been troubleshooting..

Sorry to bother you again but I have another question. In the reset circuit, what is the function of the 6.8k resistor between the op-amp output and ground? I breadboarded just this part and played around with the resistor. The only thing I noticed was a slight level increase of the pulse when I disconnect the resistor. Thank you in advance.

Dear Sir, Yes, absolutely. I am trying that but I am learning and use capture, compare of PWM, but at the age of 55, it is little too much to learn, so I felt if you have any solution I would implement it. In fact I do not need the DAC, as I just want to generate thyristor firing pulses for Phase angle control of thyristor from simple PID time-proportional output of the temperature controller. Anay ways thank you very much for your attention.

The staircase waveform looks linear on the oscilloscope (before the "steps" are carved into it). However, the main capacitor is charged by a 10k resistor on the output of the 555, rather than by a current source, so I would expect it to be exponential. Maybe it is actually exponential, but just doesn't appear to be so, or have I misunderstood something?

What is the purpose of that 6.8k resistor in relaxation oscillator section?

Are you using tantalum or ceramic caps?? Thanks, having a go myself.

Allan sir, where the heck do you get all these circuits or is it purely through experience

What is the purpose of the 6.8 kOm resistor, used in the Schmitt trigger relaxation oscillator circuit, connected between opamp output and ground? From threshold voltage point of view, this resistor is unnecessary - it does not change Vth+ nor Vth-. It only loads opamp output with more current.

Am i right if I say the 6.8K resistor forms a voltage divider with the 8.2K connected to Q1? Otherwise the 6.8K blows up my calculation of the trigger points forming the voltage hysteresis of the Schmitt-trigger circuitry.