Challenge Thread: The fastest breadboard oscillator on the mudball

[SilverSolder]

It was suggested to me that I join this competition with a ring-oscillator based contraption of mine, which I quickly reproduced on a breadboard.

So, let's have a look at my entry:

(Attachment Link)

As you can maybe make out, it is a three stage ring oscillator based on 2N3904 (chinese off-brand) and 390 Ohm load resistors. As a specialty, the output of each inverter (collector) is connected to the input of the next inverter (base) with an LED. So what can it do?

(Attachment Link)

When we apply 10V of bias to it, the LEDs will light up and it oscillates at a frequency of 35 MHz. As you can see, this design also follows the rule of a full 5V swing. The frequency suggests a tpd of 4.8 ns for each inverter, which is already "interesting", if you look up the storage time of a 2N3904 in the datasheet. Btw, with red LEDs this goes up to 55MHz, corresponding to 3ns. The same design is much faster on a PCB, so the parasitics of the breadboard take their toll.

Ok, but maybe that is not the most interesting part of this oscillator. Let's have a look at some X-Y plots where X is the input of one inverter and Y is at the output:

(Attachment Link)

At 10V we see a somewhat circular output, which suggests that the phase delay of this inverter is constant - as expected for a proper oscillator. However at 11.8 V we can suddenly see a convoluted path that almost looks random, but is clearly repeating - a limit cycle? Changing voltages further can transition from noise to different structured trajectory.

It looks like this simple circuit is acting as a chaotic oscillator. I though that was quite neat. You can find a longer write up here: https://hackaday.io/project/170697-evaluating-transistors-for-bipolar-logic-rtl/log/179154-using-a-led-as-base-resistor-chaotic-ring-oscillator.

Interesting contraption!  -  is it light sensitive?  -  it might behave differently depending on if it's in the light or dark,  or if the different LEDs can "see" each other or not....

[0culus]

Yeah, it has a standard 21.4 MHz IF out. I'm "warming up" by playing with Colpitts oscillators on the breadboard tonight. So far, with a 2N2222 and absolutely zero lead trimming I have achieved 19.5 MHz. Paltry, of course, compared to what you guys have been achieving but still faster than anything I've ever breadboarded. Is Manhattan style construction allowed?   

I think most of mine move around more than 22MHz.  Maybe yours will be more stable.   If not,   I had a look at the manual for your 8566.  It appears you may have access to the first LO on the front of the instrument as well and it has +5dBm drive.   Appendix H talks about it.

https://www.eevblog.com/forum/index.php?action=post;quote=3095892;topic=243355.100

You may be able use this as the LO for an external mixer that could directly drive your scope.   Guessing it would be a lot more stable than the open looped YIG I show.   With your GHz scope, you may be able to see something over 7GHz. 

***
Some advice, make sure you show the signal on the SA as well or it may confuse Trash into thinking you are using it for your oscillator.. 

My first attempt with the 5GHz transistor substituting for a 2N2222 was an abject fail. Absolutely nothing came out. No magic smoke though, so hopefully I didn't blow it up. I'm going to have to go back to the drawing board for this one. Attached is a plot from the 8566B with my original 2N2222 Colpitts oscillator circuit (taken with a near field probe, so the level is lower than it would be otherwise; there's a healthy DC voltage on the output which I didn't want to do anything foolish with even though I keep an 18GHz bandpass dc block on the input of the 8566B). However, it's build does not meet the rules (I had to cram a couple of leads in one hole to make it the loop size smaller) so I am *not* submitting this. I'm still quite pleased with it as a first effort though! I didn't trim any leads, either.

[tim_]

Interesting contraption!  -  is it light sensitive?  -  it might behave differently depending on if it's in the light or dark,  or if the different LEDs can "see" each other or not....

I checked the light sensitivity with the red-LEDed version. There was a very small impact on frequency with strong illumination, but not sufficient to change trajectory.
In any case, that is what I would expect, as the circuit uses currents in the tens of mA while the photocurrent induced in a LED is in the range on nA or even lower.
Maybe if you take a laser...

[0culus]

OK, stepping back from that failure, I instead redid my 2N2222 colpitts oscillator in a way that (I believe) is much closer to conforming with the challenge rules within the confines of what I have on hand. I was able to get more output and slightly better performance after snipping leads and playing with the layout. I can experiment with different inductors now to change the oscillation frequency.

Measurement conditions: again, spectrum analyzer measurements are done with a near field probe (pictured). I do not wish to take unnecessary risk feeding a big DC signal into my 8566B, as stated before. Oscilloscope measurement was done using a P6201 FET probe with 10x attenuator (bare tip, no hook) and a very short ground wire connected to my 7104 with 2x7A29 + 7B15 and 7B10 plugins. I found that passive probes detuned the circuit considerably.

Lessons learned: this is a lot of fun, and I look forward to continuing to make faster breadboard designs.  Also, passive probes are actually fairly poor performing. The beauty of breadboards is it's super easy to make changes, so attempting to exploit the well known problems of breadboards is a neat challenge. Additionally, bypass caps on the power supply line are required. Without them, it doesn't work very well at all I found.

[T3sl4co1l]

As you can maybe make out, it is a three stage ring oscillator based on 2N3904 (chinese off-brand) and 390 Ohm load resistors. As a specialty, the output of each inverter (collector) is connected to the input of the next inverter (base) with an LED. So what can it do?

Try a B-E resistor, say 470 or so.  Maybe a little ESR for the LEDs as well.

Chaos is interesting; likely it's a combination of rectification by the LEDs, and variable time constant due to the lack of B-E discharge.  Lots of nonlinearity around.

Tim

[T3sl4co1l]

Updating the screenshot -- much clearer.  Circuit changed slightly, with a shorter jumper, hence the higher frequency (and coupling kinda sucks, hence the lower power).



Tim

[tim_]

As you can maybe make out, it is a three stage ring oscillator based on 2N3904 (chinese off-brand) and 390 Ohm load resistors. As a specialty, the output of each inverter (collector) is connected to the input of the next inverter (base) with an LED. So what can it do?

Try a B-E resistor, say 470 or so.  Maybe a little ESR for the LEDs as well.

Chaos is interesting; likely it's a combination of rectification by the LEDs, and variable time constant due to the lack of B-E discharge.  Lots of nonlinearity around.

Tim

Well, actually the capacitance of the LEDs help to push the base to a low potential which helps discharching. That's why the circuit is much faster than one would expect. I have some spice-simulations on the page I linked above.

Regarding the origin of the chaos: I have to agree, it seems to be related to the relationship between delay and different levels of base charging. The behavior can be reproduced in spice, but only when using proper transistors models. E.g. the build in once from LTspice don't work, but Nexperias models do. Haven't looked in to the details yet.

[joeqsmith]

...

Lessons learned: ..... Additionally, bypass caps on the power supply line are required. Without them, it doesn't work very well at all I found.

3. No soldering except to add wires to SMT parts. All electrical connections between individual parts must be made by the breadboard contacts.

Early on I asked when a wire was no longer considered a wire but a part.  I've continue to expand and exploit the OPs allowance with a single continuous wire attaching between an SMT device and the breadboard.   

Also shown is the tuning network which is a hairlike wire hanging out in the free space.   Pretty much my oscillator is nothing more than the transistor and some wire.   You can see it setting a new record in the attached picture.

There was no design for this oscillator.  With all the parasitics, it would have taken me more time trying to model it and take a scientific approach than just taking a guess and playing with it.   I'm not even sure how I would model it.   Let's see, the human is standing on carpet and is extending their arm and fingers at these angles and they had three cups of coffee and an egg.......   

Digikey has some better parts in stock but I am beyond what I can display with the scope and closing in on the upper end of my counter. 

*****
For fun, attached directly to the LeCroy 8500A.   There's nothing that suggests the oscillator is running.    Apparently 13.5GHz is just too much for the 5GHz DSO.    

****

Also show using the downconverter with the Signal Hound.  I asked them about adding support to their software to scale the graph when using mixers, but sadly they don't seem to see a use for it.  So with the YIG still set to 8GHz,  13.5-8, we would expect to see something around 5.5GHz.   I bypassed the downconverter's splitter to gain back that 6dB and it shows up, at -70dBm.   Of course, the signal is going to be much higher as we are running the mixer way outside of its specified IF frequency. 

[0culus]

Either way, it's still really nifty. How are you mounting the transistor itself to the breadboard? Examples of particular parts on digikey you have in mind?

I did some experimenting last night using my 8672A as the RF source, and with a better quality mixer than the one I have now, I should be able to easily pick off the 8566B 1st LO and mix it down to something I can look at in time domain with my scope. Time to visit minicircuits I suppose. The mixer I have probably was not intended for having the LO frequency so high, so the IF difference freq that comes out is very weak indeed.

[joeqsmith]

I am still doing what I showed in that first video where I insert the copper wire into the breadboard, bend it 90 deg and cut it off.  I then solder the transistor to the copper wire (while the wire is still inserted in the breadboard).

Digi-key does a nice job with their search engine.  They break it down to RF FETs and transistors.  From there you can search for pretty much what ever you are looking for and in most cases, view the datasheet.   

You may be able to find a used mixer on eBay but IMO, Mini-circuits is the way to go.  Used is always a gamble and mini-circuits has a wide selection in-stock and very reasonable price.   

[BreakingOhmsLaw]

Record updated to 13.511GHz.

I second going with minicircuits. I used to order their stuff by the palet back in the days when I built test equipment for satnavs. Just works like a charm right out of the box and the performance is great for the price.

[ogden]

Early on I asked when a wire was no longer considered a wire but a part.  I've continue to expand and exploit the OPs allowance with a single continuous wire attaching between an SMT device and the breadboard.

Your achievements indeed are remarkable but as you say - you are using *exploits*. Wire-wrap and soldering breaks whole purpose of the breadboard. In your case breadbord becomes just holder, not part of the circuit. I would add strict rule that breadboard shall be part of every interconnect between components. You may manufacture inductor out of wire, but to connect it to the transistor - use breadboard, not wire-wrap or soldering.

[0culus]

But isn't microwave above a certain frequency pretty much all about exploiting parasitics instead of fighting them? I definitely think allowing soldering is fair to allow parts that are probably only available as SMD to be used. Beyond that, it becomes more questionable. Might as well build the circuit Manhattan style at that point, and get the benefits of air construction and a massive ground plane.

[ogden]

But isn't microwave above a certain frequency pretty much all about exploiting parasitics instead of fighting them?

Yes - when your microwave circuit is built on top of the breadboard. Otherwise - no.

[0culus]

I don't know, it seems to me like the rules that have been hashed out already are fair, and the OP seems fine with Mr. Smith's new record....but I admit I am a red teamer at heart and I enjoy finding creative ways to bend the rules. 

[ogden]

I don't know, it seems to me like the rules that have been hashed out already are fair, and the OP seems fine with Mr. Smith's new record....but I admit I am a red teamer at heart and I enjoy finding creative ways to bend the rules. 

Contest is as good as it's rules. Here we see that one can build microwave circuit "in the air" using breadboard as a support. To me it does not look like breadboard oscillator, sorry. My advise here would be: split into two categories. 1) free for all bend everything you can 2) every interconnect through breadboard - as it is supposed to be.

[tim_]

How about also distinguishing between large- and small signal oscillators? The original rules actually asked for a full 5V swing. (Not that I am biased here, who beats 55 MHz fully saturated swing? )

Edit: I double checked. It asks for a 5V Vpp sine. That does not make too much sense, to be honest. Either it's digital and large signal or analog and you should define SNR.

[joeqsmith]

Early on I asked when a wire was no longer considered a wire but a part.  I've continue to expand and exploit the OPs allowance with a single continuous wire attaching between an SMT device and the breadboard.

Your achievements indeed are remarkable but as you say - you are using *exploits*. Wire-wrap and soldering breaks whole purpose of the breadboard. In your case breadbord becomes just holder, not part of the circuit. I would add strict rule that breadboard shall be part of every interconnect between components. You may manufacture inductor out of wire, but to connect it to the transistor - use breadboard, not wire-wrap or soldering.

If you had taken the time to read the rules and posts, you would find that I brought up this technique very early on and it was approved.   This means that everyone, including yourself are free to exploit this technique.  You are also free to try and exploit other rules as well.  I'm not going to suck my thumb over it.   

Thinking that the breadboard or for that matter, pretty much anything else in close proximity to this oscillator has no effect is just being ignorant.  Of course the breadboard IS part of the circuit!      

It's all just for fun anyway.   So rather than concern yourself with what I have done, show us these skills of yours. 

[0culus]

OK, stepping back from that failure, I instead redid my 2N2222 colpitts oscillator in a way that (I believe) is much closer to conforming with the challenge rules within the confines of what I have on hand. I was able to get more output and slightly better performance after snipping leads and playing with the layout. I can experiment with different inductors now to change the oscillation frequency.

Measurement conditions: again, spectrum analyzer measurements are done with a near field probe (pictured). I do not wish to take unnecessary risk feeding a big DC signal into my 8566B, as stated before. Oscilloscope measurement was done using a P6201 FET probe with 10x attenuator (bare tip, no hook) and a very short ground wire connected to my 7104 with 2x7A29 + 7B15 and 7B10 plugins. I found that passive probes detuned the circuit considerably.

Lessons learned: this is a lot of fun, and I look forward to continuing to make faster breadboard designs.  Also, passive probes are actually fairly poor performing. The beauty of breadboards is it's super easy to make changes, so attempting to exploit the well known problems of breadboards is a neat challenge. Additionally, bypass caps on the power supply line are required. Without them, it doesn't work very well at all I found.

Update: I got some 2N2222As today, and I am now wondering if the ones I had are counterfeit or something. One of the new ones has considerably more gain and runs at higher frequency without touching anything else. Anyway, I'm done with that. It was a fun exercise. I'm going to look at getting some fast RF transistors and also some RF plumbing from minicircuits to support higher speed experiments. 

[ogden]

If you had taken the time to read the rules and posts, you would find that I brought up this technique very early on and it was approved.

Yes you bragged about that. By tricking organizer into accepting component interconnects outside breadboard, you spoiled whole thing. Many kids around the world are crying now because of you who came with microwave magic into kindergarden competition

[joeqsmith]

If you had taken the time to read the rules and posts, you would find that I brought up this technique very early on and it was approved.

Yes you bragged about that. By tricking organizer into accepting component interconnects outside breadboard, you spoiled whole thing. Many kids around the world are crying now because of you who came with microwave magic into kindergarden competition

When I wrote ", show us these skills of yours.  " I was actually suggesting you finally contribute something of technical merit rather than your usual trolling skills.   

I'm not sure if the OP felt tricked by my questions or not.  They would need to chime in.   While I thought I was clear with what I was asking, to the point of  using pictures of examples, I'm certainly not apposed to having them roll back the rules if they choose.   

Strange you would feel that the members here are all at a kindergarten level.   I would have guessed the majority of the technical contributors were well educated and that most understand what parasitics are, as well as what typical means on a datasheet.       

[joeqsmith]

I'm going to look at getting some fast RF transistors and also some RF plumbing from minicircuits to support higher speed experiments. 

I have a few different parts coming myself.   Maybe get that old microwave counter to overflow.   

You have your work cut out for you to get that SA of yours to max out.

[0culus]

If you had taken the time to read the rules and posts, you would find that I brought up this technique very early on and it was approved.

Yes you bragged about that. By tricking organizer into accepting component interconnects outside breadboard, you spoiled whole thing. Many kids around the world are crying now because of you who came with microwave magic into kindergarden competition

When I wrote ", show us these skills of yours.  " I was actually suggesting you finally contribute something of technical merit rather than your usual trolling skills.   

I'm not sure if the OP felt tricked by my questions or not.  They would need to chime in.   While I thought I was clear with what I was asking, to the point of  using pictures of examples, I'm certainly not apposed to having them roll back the rules if they choose.   

Strange you would feel that the members here are all at a kindergarten level.   I would have guessed the majority of the technical contributors were well educated and that most understand what parasitics are, as well as what typical means on a datasheet.       

Someone posted a picture of the 500 MHz multiplier from a Tek 184 above. L70 and L69 aren't too terribly different from what you're doing with your design. The components do not have to actually touch each other to interact in meaningful ways!

I'm going to look at getting some fast RF transistors and also some RF plumbing from minicircuits to support higher speed experiments. 

I have a few different parts coming myself.   Maybe get that old microwave counter to overflow.   

You have your work cut out for you to get that SA of yours to max out.

Yeah, it should be an interesting challenge with 22 GHz to work with (on internal mixing!). What's the limit on your counter? I also have a 20 GHz counter (5350B).

[ogden]

Many kids around the world are crying now because of you who came with microwave magic into kindergarden competition

Strange you would feel that the members here are all at a kindergarten level.

Are you serious? I did not mean that. It was joke. Notice smiley as well.

[joeqsmith]

Someone posted a picture of the 500 MHz multiplier from a Tek 184 above. L70 and L69 aren't too terribly different from what you're doing with your design. The components do not have to actually touch each other to interact in meaningful ways!

When I was very young I owned a Heathkit DX100 which didn't work.  When I took it apart, there was a wire hanging in the air near the output stage which spiked my curiosity.     Many decades later, I am still playing with wire in RF circuits. 

I'm going to look at getting some fast RF transistors and also some RF plumbing from minicircuits to support higher speed experiments. 

I have a few different parts coming myself.   Maybe get that old microwave counter to overflow.   

You have your work cut out for you to get that SA of yours to max out.

Yeah, it should be an interesting challenge with 22 GHz to work with (on internal mixing!). What's the limit on your counter? I also have a 20 GHz counter (5350B).
[/quote]

My counter has no options and can only read up to 18GHz.  GPIB would have been nice to autotune the YIG.  It's a long way off from your SA.   You can at least see what's going on vs guessing like I am.   

I like that little signal hound for the most part.  Their software interface is alright.  When I demo'ed it decoding that cheap Extech meter, I was surprised that their software was missing some key features that would have helped.  It's like this lack of support for external mixing.  Simple enough of a change but they would need to see some value in it before it would get added.      I'm not a fan of USB on test equipment but have not ran into too many problems with it.  It also has no way to power it off so I have to turn off a bus strip which powers the hub that feeds it.