Waveforms in a 74LS04 ring oscillator. - Page 1
Forum section: electronics / projects

author: hamster_nz
author_rank: Super Contributor
timestamp: March 30, 2015, 08:26:28 pm
content: I was playing around last night, and decided to see if I could measure the propagation time through a 74LS04's NOT gate.So on a breadboard I made a five-stage ring oscillator, and had a look at the waveforms. I hooked up a scope, and if I divide the frequency by five I should get the delay. So far so good.But then I decided to put a probe on both the input and output of a single gate, and see what the X/Y plot looks like. I was expecting to see something like a roughly square box, but got something far more interesting (see image - input on X, output on Y) - this was with a three stage oscillator, a five stage is even more interesting, with more little loops.So where does the negative voltages come from? It must be some sort of charge pump, but the only capacitance present is strays from the breadboard and links, and I've used the shortest jumpers possible.Adding/removing decoupling caps make little difference.Also using the extra gates to buffer the output (so the gate being probed is not part of the ring) still gives the nice swirls and - voltages.Hummm... has me thinking...

author: dom0
author_rank: Super Contributor
timestamp: March 30, 2015, 08:38:50 pm
content: Ringing due to stray inductance. Probably distributed and amplified by the multiple stages. Would need more data to analyze more thoroughly.

author: tggzzz
author_rank: Super Contributor
timestamp: March 30, 2015, 08:46:01 pm
content: Quote from: hamster_nz on March 30, 2015, 08:26:28 pmShow us a schematic and the details of how you are measuring the voltage (e.g probe type, whether HF calibrated, ground lead), and a voltage-vs-time trace.A "charge pump" wouldn't explain a 7Vpp output.

author: hamster_nz
author_rank: Super Contributor
timestamp: March 30, 2015, 09:08:41 pm
content: Quote from: tggzzz on March 30, 2015, 08:46:01 pmSchematic :build on a breadboard down one side of a 74LS04N using solid wire links.Probe type - 100mm flying wires to the on-board scope channels on on a Digilent Electronics Explorer.I am at work at the moment, but can also hook up a Rigol tonight. Do you have a hypothesis I can test?Quote from: tggzzz on March 30, 2015, 08:46:01 pmWhy not? if the real swing is 0.5 to 3V, wouldn't any charge held in stray capacitance get pushed up to 5.5v on a rising edge, and down to -2.0v on a negative edge?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 30, 2015, 09:39:37 pm
content: What's the time domain waveform look like?

author: tggzzz
author_rank: Super Contributor
timestamp: March 30, 2015, 10:09:55 pm
content: Quote from: hamster_nz on March 30, 2015, 09:08:41 pmI'm impressed that you are getting logic to work without a power supply. (Hint: the power and ground distribution details are important with medium speed logic)QuoteYes.The method you use to probe can significantly affect the trace seen on the scope; seehttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/Each input has 24pF and 100nH inductance. Seehttps://entertaininghacks.wordpress.com/2015/03/09/modified-scope-probe-improves-signal-fidelity/for an indication of the affect that might be having. A plain-vanilla time-domain trace will be revealing.(I presume youareusing 4 wires.)QuoteI have no idea what that means.

author: dom0
author_rank: Super Contributor
timestamp: March 30, 2015, 10:21:06 pm
content: I suppose he means sort of a parasitic charge pump. But it doesn't work that way, for a charge pump you have a floating capacitor connected over the supply rails, then switch it 'free', then connect it to the upper rail and the output rail. You just don't have that sort of situation anywhere here.

author: hamster_nz
author_rank: Super Contributor
timestamp: March 31, 2015, 09:34:18 am
content: So I played around some more tonight - image is attachedFor my original configuration, when the external oscilloscope probes are placed close to the pins the signal looked a lot more like I expected. I started suspecting something weird was going on with the Electronics Explorer's boards input filters, but then I attached my scope probes to the Analog inputs I got the weirdness on my oscilloscope too.So I rebuilt my circuit right beside the on-board oscilloscope inputs, using about 0.5" wires rather than 4" wires, and now things are pretty much in agreement.The X/Y plot still has some an interest loop, but it is no longer completely loopyAnd to answer my original question that I asked myself, because the three stage ring oscillator's period is around 42ns, a single gate in the 74LS04N that is about 1/6ths of that - around 7.0ns.

author: tggzzz
author_rank: Super Contributor
timestamp: March 31, 2015, 10:58:23 am
content: Add some decoupling capacitors!What's the scope's bandwidth? (sampling rate is irrelevant)Reduce the length of the scope probe ground lead: use a spring clip between the LS04 GND pin and the signal pin.

author: Richard Head
author_rank: Frequent Contributor
timestamp: March 31, 2015, 11:30:31 am
content: And don't use breadboard for a test like this. Rather use a piece of copper clad or protoboard with a solid ground plane. Use short leads everywhere, particularly ground leads.

author: dom0
author_rank: Super Contributor
timestamp: March 31, 2015, 11:50:58 am
content: Yes. My standard technique for high frequency and similar stuff looks like this and gives very good RF characteristics even for DIP packages:for DIP packages: Cut the pins off about a mm from the molded case. Then solder some SMD (0805 or 1206) 100 nF X7R caps to the supply pin(s). Solder device with caps directly to solid copper clad board.For SMD packages with pins: bent GND pins down, solder to board, stuff smallest 100 nF caps you have under supply pins.SMD packages without pins: glue flipped on board, use smallest caps directly by the packageHot packages with extra exposed pad need extra care. E.g. cooper wire for heat transfer.

author: hamster_nz
author_rank: Super Contributor
timestamp: April 01, 2015, 10:29:22 am
content: Using Spring clips on the probe made little difference, and removing/moving/adding more decoupling caps made no visible difference (the original cap is just out of photo). The scope is 100Mz, so the approx 25 MHz signal is close much at the limit.Just to check, I a found a better source to test on, using equally shoddy technique. The following are from two scope probes just clipped to pin headers that are inserted into an FPGA dev board's PMOD connector. The board is generating two 25Mhz, with 120 degrees of phase difference.The waveforms look a bit better, but not much like square waves.I then discounted all the advice above, and made a couple of simple changes, and got the "fixed" waveforms seen below. Anybody want to hazard a guess at what I did?

author: nuno
author_rank: Frequent Contributor
timestamp: April 01, 2015, 10:36:53 am
content: Added termination resistors?

author: Richard Head
author_rank: Frequent Contributor
timestamp: April 01, 2015, 11:04:50 am
content: Lowered the supply voltage?

author: tggzzz
author_rank: Super Contributor
timestamp: April 01, 2015, 11:55:36 am
content: Quote from: hamster_nz on April 01, 2015, 10:29:22 amIn which case it cannot have been a decoupling capacitor. I suggest you do some research on how decoupling capacitors work, in particular placement and capacitor type/value.I suspect your background is software or VHDL/Verilog or audio frequency; mediulm speed digital has different issues.QuoteNo. Provided you understand what you can and cannot expect from a 100MHz scope, you can usefully inspect signals that are significantly higher than 25MHz.Of course analogue scopes are conceptually simpler than digital scopes, and therefore there is less scope (ho ho) for "interesting" surprises. But please don't let this degenerate into a tedious pointless analogue-vs-digital discussion; both have well known advantages and disadvantages.

author: hamster_nz
author_rank: Super Contributor
timestamp: April 01, 2015, 05:49:31 pm
content: Quote from: nuno on April 01, 2015, 10:36:53 amBingo - carefully wedged a couple of empirically selected 120 ohm resistors across the header pins.

author: hamster_nz
author_rank: Super Contributor
timestamp: April 01, 2015, 06:18:35 pm
content: Quote from: tggzzz on April 01, 2015, 11:55:36 amAgreed, but it is getting to close to the limits of a 100MHz scope to look at the shape of the edges on a 25MHz square wave. If it was a 50Mhz signal I was looking at I say I would be asking for trouble...Oh, and as for the decoupling caps, I agree that they are needed, but in this case they made no measurable difference to the performance of circuit.In my original playing around used 0.1u Tants - either over the chip and/or on the power rows, so I moved them a little out the way. They made zero difference in the visible waveforms, and only the tiniest difference in the frequency of the ring oscillator, speeding up switching by a small percentage (which was what I was really interested in).I had the benefit that that only one gate is switching at a time, which is rather non-typical for digital logic, and I'm using a 'S' part...However, I could have been doing it all wrong. Do you have a 74LS04 kicking round - perhaps recreate it see what effect proper decoupling it has.

author: tggzzz
author_rank: Super Contributor
timestamp: April 01, 2015, 08:41:16 pm
content: Quote from: hamster_nz on April 01, 2015, 06:18:35 pmAgreed, but at least you can spot timing differences to <<10ns.Quote... except that they changed theeffectivethreshold voltage, which manifested itself as a frequency change...QuoteWell, I've recently done something similar to teach people about scopes and probing techniques, using 74S04 and didn't see anything like your traces. Well, that's not quite true - the waveforms were horrible (-1V) when using a 6" ground probe ground lead, which was the main point of the exercise.The significant difference was that I used dead-bug technique on unetched PCB, and had a decoupler from pin 14 to the PCB. There were no pullup/down/termination resistors, because they are theoreticallyandpracticallyunnecessary with electrically short signal wires.

author: tggzzz
author_rank: Super Contributor
timestamp: April 01, 2015, 08:57:37 pm
content: Quote from: hamster_nz on April 01, 2015, 05:49:31 pmBasically your experience surprises me to the extent that I know there's something amiss. What do you mean "across the header pins"? If you mean as a series termination resistor, then that would, of course, reduce the peak current transients thus making the decoupling less critical.I recently built an "edge" generator using multiple 74alvc1g14 gates, which have amuchfaster risetime than LS series (probably around 1ns) and a much higher symmetrical output drive capability. Each gate had its own 10nF 0603 decoupling capacitor. The circuit was one '14 as a relaxation oscillator, driving one '14 as a buffer, driving 6 '14s in parallel. Half of those simply had their outputs paralled up so that any reasonable capacitance was a non-issue. The other half approximated a 50ohm output by each gate having a 130ohm series resistor, and the other side of the resistors connected in parallel to the "50ohm" output (150/2 => 50, of course).The overall output was extremely clean when driving either a standard 150MHz high impedance probe,providedthe ground lead was short. See the relevant oscillograms with short and long ground leads athttps://entertaininghacks.wordpress.com/2015/04/23/scope-probe-accessory-improves-signal-fidelity/The signal was identical when driving a 1.5GHz 500ohm low impedance Z0 probe, and identical with the 50ohm output.Hence I can only conclude that the lousy breadboard construction is the root cause of your waveforms.Soon, I hope, I'm going to get around to building a homebrew 2GS/s 2GHz scope, so then I'll be able to see the edges of the 74alvc1g14

author: joeqsmith
author_rank: Super Contributor
timestamp: April 02, 2015, 01:03:51 am
content: I'm not sure why you care about the waveforms. Can't you just use your counter to measure the delay? Or, be lazy like me and pull the numbers from the data sheets?What happens when you use all the gates and buffer the signal? In other words, don't add extra load to the oscillator. Just buffer, then measure. Does the frequency change?

author: tggzzz
author_rank: Super Contributor
timestamp: April 02, 2015, 08:11:09 am
content: Quote from: joeqsmith on April 02, 2015, 01:03:51 amI don't think he does care: he started the OP with "I was playing around last night". And that's just fine by me - it is surprising how much you (me, everybody) learns by doing something out of the ordinary.After all, the most exciting sound in science isn't "Eureka!" - rather it is "That's ... funny...?!"

author: hamster_nz
author_rank: Super Contributor
timestamp: April 02, 2015, 09:45:24 am
content: Quote from: tggzzz on April 01, 2015, 08:41:16 pmSo tonight I dead-bugged it, probed with a 10x probe and spring clip, then used probe with hook and ground wire, then snipped out the capacitor and used the hook and ground wire again.Deadbugged it tonight - I didn't have and blank PCB to use as a ground plane so it was hanging in free air. Frequency was 33MHz, up from early/mid 20MHz when on a solderless breadboard - and strangely enough as earlier, snipping out the 0.1u cap made about 1% difference to the frequency.Not that I'm saying you don't need decoupling, but it makes very little difference in this circuit....

author: tggzzz
author_rank: Super Contributor
timestamp: April 02, 2015, 10:38:26 am
content: Quote from: hamster_nz on April 02, 2015, 09:45:24 amAs you noted previously, with a 33MHz fundamental and 100MHz scope, the 3rd hamonic will be 3dB down.If I was doing that circuit, I would try to ensure that the period is sufficiently long that any edge effects have dies out before the next edge occurs. With my 'S04 circuit I inserted a short RC delay between gates 1 and 2, connected gates 2->3->4->5->1, and observed outputs of gates 4 and 5. Despite being an 'S04 not an 'S14, the "analogue" input caused no problems.Having said that, LS had the reputation of being "simple to use" whereas S was "lookout for dragons" territory for the obvious reasons.I remember back in '79-'80 my project built a ~100 LSTTL ic double-sided PCB, paying very good attention to power layout and decoupling. It worked flawlessly first time, and other teams specifically told us that surprised them. I've always been very attentive to electromagnetics ever since

author: nuno
author_rank: Frequent Contributor
timestamp: April 02, 2015, 11:08:32 am
content: Get a better capacitor (and still use the spring)?Use 10n or 1n cap, use 2 or 3 in parallel.You can also try this, with and without the capacitor: double or triple the power supply wires length.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 03, 2015, 02:47:40 am
content: Pulled out some old DIP chips to try and replicate your setup. Shown using Motorola SN74LS04N, three gates for the ring, then two more gates to buffer then invert. Just using some RG58. Bypass cap is 0.47uF ceramic. Pictures shows the mess.First two plots are using 10X probes with the long wire and no bypass.Plot three is no bypass, using coax, Wavecrapper set to 50 ohm inputs.Plot four is the same as plot three with the bypass stuck in. Bypass if we call it that, still appears to have some effect.1/(2*3*40MHz) = 4nS propagation

author: joeqsmith
author_rank: Super Contributor
timestamp: April 03, 2015, 05:18:56 pm
content: Setup a quick test changing from the whiteboard to perf board. Using same 3 gate ring and buffer. Added termination. Didn't have any 450 ohms, so used a couple of 1K 1206s in parallel. Pulled up the unused gate rather than grounded as shown.Still a mess, but should speed up the oscillator.

author: SeanB
author_rank: Super Contributor
timestamp: April 03, 2015, 05:27:32 pm
content: I think that wet tantalum is rather more expensive than the rest of the board though......... Definitely overkill using that 1990's vintage part, though it will still have a low ESR and will still pass all it's military certification tests.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 03, 2015, 05:48:33 pm
content: Gotta love the nice sharp pull-up of a CMOS gate, compared to the old weak TTL version...

author: SeanB
author_rank: Super Contributor
timestamp: April 03, 2015, 05:48:58 pm
content: Now you need to get some ECL devices and try them.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 03, 2015, 06:18:21 pm
content: Anyone want to start a donation fund for purchasing some Hittite gates?"The scope can't tell if it's running... let's point the camera at it and see if it's emitting light instead?"...Tim

author: SeanB
author_rank: Super Contributor
timestamp: April 03, 2015, 06:26:16 pm
content: Quote from: T3sl4co1l on April 03, 2015, 06:18:21 pmIt only does 28GHz...............https://www.hittite.com/products/view.html/view/HMC842LC4BAnd might go as high as 45GHz.Don't think dead bud style will work here, and as it is in a ceramic carrier only the price might be a little on the high side. wonder if you can ask AD for a sample device.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 03, 2015, 07:01:28 pm
content: Sorry, I'll have to leave the ECL test to someone else. My antique stash of TH parts is pretty limited.Swapped out the Wavecrapper. First plot showing the Motorola SN74LS04N, second the RCA CD74HC04E.The third plot is an old CMOS 4000 series, Motorola MC14069UBAL. 27.8ns Way better than I would have guessed.....

author: SeanB
author_rank: Super Contributor
timestamp: April 03, 2015, 07:29:00 pm
content: Unbuffered CMOS is always faster, even if it has an output that will barely qualify it as digital. Supply it with 18V and it will be even faster, though it might also run quite hot as well. RCA CMOS was qualified to 20V, as opposed to the 18V of the other suppliers. The rise and fall time is very dependant on supply voltage as well, which can be an issue. 2V supply and most would not work over a few kHz.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 03, 2015, 08:22:15 pm
content: Remember when.... databooks? Finding the book was faster than searching the internet.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 03, 2015, 08:28:54 pm
content: Top is running the MC14069UBAL at 3.3 followed by 10, 15 & 18 volts. Those wide thresholds made it idea for some applications.

author: albert22
author_rank: Regular Contributor
timestamp: April 04, 2015, 04:47:07 pm
content: Here is a similar ring oscillator, by varying the supply voltage they turned it into a VCO.What can be expected of something like it?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 04, 2015, 05:11:09 pm
content: Seems unlikely that it would be so linear, but it's worth noting a similar thing is used for traditional PLLs and DLLs such as you find in embedded CMOS (MCU / FPGA / radio / etc.) stuff. What's different is, the gates themselves are controlled from current mirrors (with a cascode circuit), thus varying the slew rate on the switching node (which has a ~constant capacitance), so you'd expect reasonable linearity.Tim

author: JoeN
author_rank: Frequent Contributor
timestamp: April 05, 2015, 03:15:10 am
content: What if this circuit was built out of ECL instead of TTL? Would that work? What approximate frequency would you expect to see on the output? Example IC for implementation:http://www.onsemi.com/pub_link/Collateral/MC10EL04-D.PDF

author: joeqsmith
author_rank: Super Contributor
timestamp: April 05, 2015, 04:24:16 am
content: Quote from: albert22 on April 04, 2015, 04:47:07 pmNot thinking this would be a real good source but depends what you need. Even if you ran it closed loop with a little PI controller, hardly seems worth it.It was easy enough to automate this test with Labview. The data should give you some idea of the open loop non-linearity. I used the same 3 stage oscillator used for the previous tests. The power supply voltage was swept from 1.0 to 5.2 volts in increments of 0.1. To get some decent numbers, a counter running off a GPS was used to measure the output frequency. I ran all of the same devices. That old RCA part again looks very good for linearity.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 05, 2015, 05:30:43 am
content: Wow, the HC keep going below 1V... (at room temperature, anyway!). I've heard of them recommended for micropower apps at say 2V, where they're slower than CD4000 at 5V... didn't think they'd keep going that low though.Tim

author: joeqsmith
author_rank: Super Contributor
timestamp: April 05, 2015, 06:46:28 am
content: I have updated the voltage vs frequency graph to include the three new parts.Notice the Fairchild F part tops out over 100MHz! I don't remember anything faster than the Fs back then (in the 7400 series). Also seem to remember them being more sensitive to ESD.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 05, 2015, 06:56:29 am
content: Link to the data sheet:https://www.fairchildsemi.com/datasheets/74/74F04.pdfAttached to the LeCroy 8500A with the semi rigid as before. Sub nS fall times now. Expected the weaker drive.

author: tggzzz
author_rank: Super Contributor
timestamp: April 05, 2015, 07:13:00 am
content: Quote from: SeanB on April 03, 2015, 05:48:58 pm... and stop measuring time in Siemens. Most people prefer time to be measured in seconds.

author: tggzzz
author_rank: Super Contributor
timestamp: April 05, 2015, 07:14:31 am
content: Quote from: T3sl4co1l on April 05, 2015, 05:30:43 amI was more surprised at the voltage at which the LS device ran.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 05, 2015, 07:42:30 am
content: Quote from: T3sl4co1l on April 05, 2015, 05:30:43 amAt least the two parts from Motorola and National did. The RCA fell a little short.Plot showing the Fast part running at 5.4 volts stuck to a Peltier then cooling it. With a little higher voltage and a little more cooling, it may break 110MHz.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 05, 2015, 07:55:56 am
content: Quote from: JoeN on April 05, 2015, 03:15:10 amThat seems like a good experiment for you to try and then post your findings.I was trying to stick with the same pinout and package that the OP was using.

author: SeanB
author_rank: Super Contributor
timestamp: April 05, 2015, 08:22:27 am
content: I remember some boards that used a 74F 138 as a logic decoder, just so they could get those extra few ns of propagation delay down, so that they could use a slower and much cheaper SRAM device. Important if you were making a 128k bank switched ram board and wanted the slower RAM battery backed, the difference in leakage current for the slow parts as compared to the faster ones was actually quite significant. Still ran at sub 4MHz though, using a Z80 processor. There was a note in the service manual that you had to use a F device in those address decoder locations, and use LS or S chips in the rest of the decode logic as well. Supply fail was detected with a simple transistor and zener diode fed from the 8V logic supply, so you would write protect the RAM array when the 8V bus fell to 6V. The transistor drove a CMOS inverter that simply deselected the alternate chip select, putting the RAM to low power mode.Those days when a 6116LP3 chip was considered both a large chip and a low power one as well.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 05, 2015, 05:58:06 pm
content: After the hour warmup, I collected data for an hour. The frequency drifted almost 250KHz. Lower graph is showing the power supply drift, about 2mV. Keep in mind from previous data, frequency went up with voltage, not down. Suspect this is more temperature than anything.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 05, 2015, 06:01:25 pm
content: From the data sheet, the F part will handle up to 5.5 volts. To show the effects on the frequency with voltage, I stepped it up few times. Notice how it jumps in frequency then slowly drops off.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 05, 2015, 06:09:25 pm
content: I pushed the supply up higher, then took a cotton swap with alcohol on it, at dabbed it onto the IC. You can clearly see how the temperature effects the frequency. To see if the part would break 110MHz, I raised the voltage to 5.500. This was not enough even with the alcohol.Placed the Peltier on a fair sized heat sink and laid it over the IC. To the right, you can see the oscillator speeding up well beyond 110MHz as it is cooled. Final temp was +12C.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 07, 2015, 02:55:13 am
content: Before testing the new parts, I wanted to see if there was any more speed gains in the F ring oscillator with temperatures below +12C. Next few pictures show my free temperature chamber I put together tonight.Old computer heatsink. Thermal epoxy the peltier to the heat spreader. Epoxied aluminum block to the peltier.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 07, 2015, 03:00:27 am
content: Built up a few layers of insulation. Hot glued together. Insulation block on the cover is used to press the perf board (IC lid) against the aluminum block.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 07, 2015, 03:14:01 am
content: After all of that, the results were less than impressive. With the F part running at 5.5 volts, I can now get the temperature down to -7C, or about 19 degrees lower than before. The speed was a wash at 110.97MHz.I then heated the part to 50C and kept the voltage at 5.5. After it stabilized, it was around 104.28MHz.A lot more stable than I would have guessed.

author: dannyf
author_rank: Super Contributor
timestamp: April 07, 2015, 11:13:47 am
content: Those are really good numbers.One potential (but minor) issue I see is that on a typical vcxo, the control signal is a low-power signal. Here, it needs to be a power signal - being able to supply 10-20ma minimum.That can be cured, however, with a emitter follower or even a regulator.

author: JoeN
author_rank: Frequent Contributor
timestamp: April 08, 2015, 03:17:00 am
content: Following this thread I built myself an oscillator, actually four so far, that work well out of 7404, 74LS04, 74LS14, and 74HC04 ICs (they all run 19-22Mhz except the Schmitt trigger one which runs more like 12Mhz). I took the advice of the person who told me I should be the person to test out an ECL circuit and I am going to attempt to build that too, but I don't know anything about ECL so I think I will ask for some advice here. I don't have an ECL inverter but I do have the part MC100EP105 (http://www.onsemi.com/pub_link/Collateral/MC10EP105-D.PDF) which is AND/NAND and can be made into an inverter by feeding the output of one stage into both the inputs (one differential pair to two differential pairs) of the next stage. So this is the plan:I0->I1 (first "inverter" to second)Q0 ->!D1a 29->22Q0 ->!D1b 29->20!Q0->D1a 30->23!Q0->D1b 30->21so, pin 29 to pins 20 and 22, pin 30 to pins 21 and 23I1->I3 (second "inverter" to third)Q1 ->!D3a 2->14Q1 ->!D3b 2->11!Q1->D3a 3->15!Q1->D3b 3->12so, pin 2 to pins 11 and 14, pin 3 to pins 21 and 23I3->I0 (third "inverter" back to first)Q3 ->!D0a 6->26Q3 ->!D0b 6->24!Q3->D0a 7->27!Q3->D0b 7->25so, pin 6 to pins 24 and 26, pin 7 to pins 25 and 27And a tap off of D0a as the oscillator output. Vcc = +5V, Vee = 0VI have to use an adapter board and traces are probably longer than they should be. For traces above I will cut the wires to the same length to equalize propagation delays regardless of if they need that length or not. Unfortunately, the adapter board itself has varying lengths on the traces.Is it that simple or am I being naive about ECL circuits? Thanks.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 08, 2015, 03:31:16 am
content: If you have any kind of trace length (i.e., comparable to the rise time -- 100ps is only 2cm of trace or coax), you will need termination resistors. And I forget, but suspect, that ECL needs/wants a termination resistor for correct bias anyway. Follow the datasheet instruction with termination resistors and terminating voltage: bypass the termination resistor to ground as short as possible, using chip resistors/capacitors and ground plane. The termination supply can be generated with an op-amp or something like that; it should be capable of bidirectional current flow (so, don't just use an LM317 or something). Be sure it can handle plenty of current.Likewise, your maximum frequency will be limited by propagation delay of the gates as well as the interconnects. Should still be around a GHz though!Tim

author: hamster_nz
author_rank: Super Contributor
timestamp: April 08, 2015, 03:35:18 am
content: Quote from: JoeN on April 08, 2015, 03:17:00 amIf you want to have a fun read about some interesting uses of ECL logic, have a look at the internals of a early Crayhttp://american.cs.ucdavis.edu/academic/readings/papers/CRAY-technology.pdf- full of interesting detailed stuff like:Quote

author: JoeN
author_rank: Frequent Contributor
timestamp: April 08, 2015, 03:43:48 am
content: Quote from: T3sl4co1l on April 08, 2015, 03:31:16 amHa, this is what I was thinking the issue was. I am going to have to have a small PCB made to try this out. Good thing boards are only $5 a square inch these days for three. Not only is there really no way to breadboard this circuit, it sounds like it would be next to impossible even with solder on a perfboard using a QFP-32 adapter, which is what I was thinking of doing.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 08, 2015, 03:50:30 am
content: A QFP adapter, maybe not; but building it up on copper clad wouldn't be impossible. Just tedious.If you have shaky hands, hand-carving a board is probably beyond your scope, but if not, 0.05" pitch traces are easy to create with a utility knife. Vias are probably harder (you need to poke a hole and solder or rivet in something conductive!).Tim

author: joeqsmith
author_rank: Super Contributor
timestamp: April 09, 2015, 01:12:59 am
content: Quote from: JoeN on April 08, 2015, 03:17:00 amSounds good! Looking forward to seeing what you come up with.Added a little more insulation to my chip cooler.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 09, 2015, 01:19:35 am
content: Ran the voltage sweeps for the four new parts. See attached. The Motorola MC74AC14N is the second fastest part I tried at about half the speed of the F. Wanted to see what the edge rates on this thing look like. Pretty good.Changed cables to allow me to use the DSOs with the cooler.

author: dannyf
author_rank: Super Contributor
timestamp: April 09, 2015, 01:26:17 am
content: it doesn't have to be a ring (3x gates). One gate works just fine - connect its input to its output.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 09, 2015, 01:45:04 am
content: Quote from: dannyf on April 09, 2015, 01:26:17 amI think people understand that. If you looked at the LVDS oscillator I showed, that was one gate.Cooling the Motorola part to -10C slightly improved the fall times and frequency.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 09, 2015, 03:50:29 am
content: Going back and looking at the low voltage operation, the Motorola MC74HC04N won out. I ran the part at 22, -5 and 50C. Part runs at a slightly lower voltage at higher temperature. 0.846 volts is about it with sub KHz output.

author: JoeN
author_rank: Frequent Contributor
timestamp: April 09, 2015, 06:21:56 am
content: Quote from: T3sl4co1l on April 08, 2015, 03:31:16 amOK, here is my schematic and on the PCB I try to keep the traces about equal length and the resistors very close to the pins they are terminating. Am I even close to being right on this? I read the ON guide to termination as well as one from Micrel and as far as I can see this seems to be the way it is done. One guide seems to say that you don't need bypass caps for ECL because it is inherently balanced but I included two anyway. Device is MC100EP105. Resistors and caps are 0805. Resistor is metal film 1%, caps are ceramic. The output is an SMA edge connector. Any idea about what I should do for unused inputs and outputs on the unused gate?

author: joeqsmith
author_rank: Super Contributor
timestamp: April 09, 2015, 10:09:44 pm
content: Looks like you are off to a good start. Check the pg 8 of the data sheet you provided the link to for the termination. VTT=VCC-2.0. I would use that last gates to drive the DSO. I checked and only have the real old 80s Motorola book that covers the 10K and earlier. Does not seem like you would want the series terminator but could be wrong.

author: JoeN
author_rank: Frequent Contributor
timestamp: April 09, 2015, 11:10:12 pm
content: Quote from: joeqsmith on April 09, 2015, 10:09:44 pmSo, on closer inspection, you recommend terminating it this way:So it recommends terminating to Vtt instead of Vee, right? Vtt would be 3.0V in this case. Should I throw on a regulator to create that voltage?And why no series termination? I see 50 ohm resistors in series on this schematic so that is why I put them on my schematic. I could leave the 0805 footprint in there and drop in a 0 ohm resistor and see if it matters. Does that sounds OK or would a 0 ohm resistor affect the circuit? I'm going to get 3 boards in any case and I have five of these ICs total.Micrel seems to recommend terminating to Vee which is why I did that at first:http://www.micrel.com/_PDF/HBW/App-Notes/termination.pdfBy using the last gate to "drive the DSO" are you meaning the RF output and assuming an oscilloscope on the output? What advantage does this give, will having a buffer square up the output a bit since it is no longer also driving a gate?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 10, 2015, 02:29:52 am
content: No, those aren't series terminations, those are indicating to use 50 ohm transmission lines.Tim

author: joeqsmith
author_rank: Super Contributor
timestamp: April 10, 2015, 02:32:05 am
content: I am only suggesting to check the data sheet. Micrel app note you link to, see figures 3&4. Take the time to read it.Zo is not a resistor.Adding any discontinuity, like a zero ohm jump will cause some reflection. Higher speeds, need to pay more attention.You could make a few different boards on the one panel to try different ideas out.QuoteYes. Isolation.I have not used ECL in many years. You should have no problem getting something to work on a circuit board. This is a very short video I put together showing a single PECL FF on an a VERY crude X-acto knife board. The videos not real exciting but does show you can clock some of them well into the GHz range as mentioned.https://www.youtube.com/watch?v=k1pUlJwJzAI&feature=youtu.beLooking forward to seeing what you get working.

author: JoeN
author_rank: Frequent Contributor
timestamp: April 10, 2015, 02:36:03 am
content: Quote from: joeqsmith on April 10, 2015, 02:32:05 amThanks for the info. If you say those series resistors are definitely not necessary then they come off, no problem. Probably save a few cents on the board and keep the traces a bit shorter. My idea of a regulator to supply 3.0V for the 50 ohm parallel terminator resistors, is that a good idea? If so, maybe I can get this design out tomorrow to OSH and then we have to wait a couple of weeks. Thanks for your help.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 10, 2015, 03:11:25 am
content: From your Micrel note:QuoteI am not sure how the Micrel note applies to the parts you are playing with.QuotePersonally, I would just use what is shown in Fig 3 or 4 and forget using another supply. Doubt you really care about the added power. Really if you want to play with it, I would recommend you try all three. Then one without termination and one with series termination just to see what the effects are. Seems like all 5 circuits should fit on a small board.

author: GK
author_rank: Super Contributor
timestamp: April 10, 2015, 10:18:05 am
content: Potato semi's so called GHz logic might be interesting to play with/try. Parts can be had from their on-line store in small qty.http://www.potatosemi.com/

author: dannyf
author_rank: Super Contributor
timestamp: April 10, 2015, 11:29:10 am
content: 74HC132 -> 120Mhz for single gate and 40Mhz+ for 3 gates, all at 5v. 3 gates work down to 2Mhz @ 1v and 60Mhz+ at 10v (yes, 10v).

author: JoeN
author_rank: Frequent Contributor
timestamp: April 10, 2015, 08:38:27 pm
content: Quote from: GK on April 10, 2015, 10:18:05 amI am sort of surprised I haven't heard of them and never got a hit on them on eBay during other searches. Sort of interesting. I do think they need a new logo and name though, the current choices are pretty lame. I know it doesn't matter as far as their product goes, but really it does actually matter at some point to generate enough confidence that the company is a serious entity that will be there in a few years. I wonder if they have any serious customers.

author: tggzzz
author_rank: Super Contributor
timestamp: April 10, 2015, 09:02:11 pm
content: Quote from: JoeN on April 10, 2015, 08:38:27 pmGood question. Personally I am put off by them still having the Vcc/GND pins as far away from each other as they can. I disliked that in the late 70s, and haven't seen any reason tochange my mind.

author: dannyf
author_rank: Super Contributor
timestamp: April 11, 2015, 12:09:13 am
content: For hobby uses, it seems to be OK - whenever ebay parts are OK, those potato chips should be ok too.Anything above that, I would think twice about using them.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 11, 2015, 01:11:10 pm
content: Quote from: dannyf on April 10, 2015, 11:29:10 am1/2*120M*1 = 4.2nS = 1/2*40M*3. Yea, the math works.Sounds like your numbers are on par with mine. I am a bit surprised it would run at 10 volts. What is the exact part you used? I have a few duplicate parts I could run up to failure and see what I get.The OP had started out with 5 gates, then dropped it to 3. I am not sure why but guess they wanted it running slow enough that they could make the measurement with the equipment they have available.With JoeN trying ECL, we could see some faster numbers. It will be interesting to see what they get working.

author: dannyf
author_rank: Super Contributor
timestamp: April 11, 2015, 08:15:39 pm
content: The HC132 I used earlier was actually an AHC132 (SN74AHC132 by TI).I drop'd in a HC00 (Philips) and got similar results (95Mhz vs. 120Mhz, one gate only).

author: dannyf
author_rank: Super Contributor
timestamp: April 12, 2015, 12:29:49 am
content: Tried some MM74HC00 from ST. 75Mhz tops (1 gate, 10v).This thing can be made into local oscillators. With a mixer + LPF, you get a direct conversion, pot-turned radio.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 12, 2015, 03:16:29 am
content: Quote from: dannyf on April 12, 2015, 12:29:49 amThis would make IMO an interesting thread.

author: dannyf
author_rank: Super Contributor
timestamp: April 12, 2015, 01:20:05 pm
content: current consumption for the MM74HC00 part:12ma @ 5v;56ma @ 12v (yes, 12v)250ma @ 20v (yes, 20v, for a 5v part).

author: Zero999
author_rank: Super Contributor
timestamp: April 12, 2015, 04:42:11 pm
content: At what voltage does it release magic smoke?

author: joeqsmith
author_rank: Super Contributor
timestamp: April 12, 2015, 05:34:01 pm
content: When you measure the current, are you using all four gates? Curious how much is the loading and how much is the part.

author: dannyf
author_rank: Super Contributor
timestamp: April 12, 2015, 06:33:46 pm
content: All four gates were used.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 14, 2015, 01:47:30 am
content: I set the jig to sweep from 2.6 to 24 volts, with the current limit set to 6 amps. It did not provide me with the excitement I had hoped for. The counter's input impedance was set to 1Meg rather than 50 ohms to limit the load current and prevent damage to the front end. Nothing else was changed in the test setup.Looking at the 4069, you can see how the frequency actually starts to fold back. This is very reproducible. This is the only part the survived.The 74HC04 didn't just fail. It sort of slowly died after 11.2 volts.The 74AC14 died real quick after 8.4 volts. You can see it trying to stay alive for a few more cycles..Damage2 is zoomed into the area where the HC and AC devices failed.No smoke, no plastic fragments.....

author: joeqsmith
author_rank: Super Contributor
timestamp: April 14, 2015, 11:59:59 pm
content: Found an duplicate Harris HC part which ran all the way out to 15.2 volts. Notice again how the frequency was falling off just prior to failure. Again, no real excitement.Grabbed an old Fairchild TTL part thinking that would certainly actually blow up... It did!What's real interesting is how the TTL parts frequency fell way off, then it takes such a radical jump, rolls off again, then dies a flaming smoke filled room kinda death.If you found an HC part that runs to 20 volts as you suggest and is linear, stick with that part.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 23, 2016, 06:00:34 pm
content: An old National 54F04 military device. Not as fast as the Fairchild F04. Also ran it up to 110 and down to -12C.

author: David Hess
author_rank: Super Contributor
timestamp: September 23, 2016, 08:55:28 pm
content: In the past when building these types of test circuits, I usually included a fast discrete JFET or bipolar buffer to drive a 50 ohm transmission line directly to the oscilloscope. I guess now there are some integrated buffers or operational amplifiers which could do the same thing.