The resistor is right at the base of the transistor. It's hard to miss.
Node names are free in LT Spice. I name them something meaningful if I want to see the node name on a plot or a DC analysis. I can name the resistor RbQ2 or something, too.
I'm not likely to forget, but Spice is useless in determining the value that will kill oscillations. It can establish that some value won't slow down normal operation too much. I tend to use 33 ohms.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On a sunny day (Tue, 16 May 2017 08:12:13 GMT) it happened Jan Panteltje wrote in :
So.... been doing some testing, 75 Ohm load:
Since I do not have one of those defective scopes, the ones that only work every now and then, sometimes call 'sampling scopes [1]' by their users, I use a trick
to see what comes out as harmonics.... of the 60 MHz square wave I feed in:
Hope this helps.
Any more questions please build it yerself, it is not that hard.
Thermal runaway? No sign of it, not with these voltages and 75 Ohm load. So .. else glue some trannies together so they track. nuf said.
[1] I do have one but it is slow:
But you have already forgotten. Remember the tiny pcb you made where you didn't have enough room to add parasitic suppression resistors?
As far as helping determine the value needed, finding a value that won't slow down normal operation too much is exactly what I meant.
We agree.
On a sunny day (Mon, 15 May 2017 19:50:40 +0100) it happened "Kevin Aylward" wrote in :
Higgs stuff is way, way to complicated for us engineers. However, empty space, most certainly, isn't empty. Things are popping in and out of existence all the time.
Lots of mass related problems. What causes inertia? Is it mass sending out gravitons that boomerang back to oppose motion, or a sea of of vacuum stuff. I don't buy the Mach principle bit. Its all mystery darkness...
I have not met Pete, however, I did get a signed letter from him around
2,000. I was thinking about applying to do a Ph.D at Edinburgh Uni. The idea faded though.-- Kevin Aylward
When you're doing fast stuff, and every picosecond is worth money, adding any resistor in the signal path, or wasting any space, is a defeat.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Am 16.05.2017 um 20:16 schrieb John Larkin:
Yes. I second that. In simulation, my 4*IF3601 preamp is definitely stable, but in real live:
<For most frequencies outside of the Smith diagram, if you look into the input. Any L on the input with small enough resistance will oscillate, including ferrite beads. The usual gate stopper is not possible for obvious noise reasons.
:-( Gerhard
(Sorry for the choice of colours.)
In SS. its place testpoint on pin. Done.
Yeah, I haven't gotten round to auto sign inversion on two terminal devices. However, press m (mirror) of f (flip vert) and run again !
SS automatically puts in zero volts source in .subckts, so again, its place testpoint on pin. Done.
However, I don't really agree that the is a huge learning curve in spice. Its all GUI for the most part. The bulk of spice is all hidden. If one can't figure out that running 10,000 cycles at small time steps is going to take a long time, I doubt if one should be using spice at all.
-- Kevin Aylward
Nice marketing, poor engineering. When you are trying to ship fast stuff, and it oscillates, that is a defeat.
You have to fix it, and you had no room.
You should have expected it and solved it before making lots of pcbs. Coupled high speed transistors or facing long leads is a potential disaster.
I'll bet you check now.
Design some picosecond stuff yourself. And show us. And don't be an asshole.
It got fixed and we got paid.
I've been doing picosecond electronics for decades, and sold a ton of it... more as time goes on. Sometimes things happen on the first PCB rev of a difficult design. We fix it. No big deal.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
I was doing femtosecond stuff in 1970. Your insult about being an asshole has no effect. Stop being a jerk.
So what heppened to your picoseconds?
As I said, you should have expected it, and you did not. So much for your claims of picosecond electronics.
In fact, nothing you do is in picoseconds. Perhaps tenths of a nanosecond, but not much more. False claims, but they can make a lot of money.
Is that to handle the shield? How would you model UTP?
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
That model is about right for shielded CAT6. UTP is sort of shielded by the universe, in the sense that it still has odd and even modes. You don't care much about the even mode in Ethernet, since the signals are transformer coupled and nicely balanced on both ends.
So a single LT Spice TLINE or LTLINE would be an OK model for UTP. LTLINE still wouldn't get the skin loss right.
I have an application that uses a shielded twisted pair but has unbalanced terminations, so both the odd and even propagation modes matter some. I'm trying to get the customer to send me a hank of the actual cable, so I can TDR it and tweak my model.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Do tell. "Femtosecond stuff" such as reading the newspaper by 600 THz light, maybe?
I'm pretty sure I'm the only one in this group who has actually built electronics that respond on fs time scales (optical antennas coupled to metal-insulator-metal tunnel diodes--basically crystal radios for light).
Picosecond lasers were the state of the art in the late '80s. One or two groups had used pulse compression to make pulses at the 10-20 fs level as a hero experiment by then, but that sure wasn't happening in 1970.
So what "femtosecond stuff" were you doing in 1970?
Cheers
Phil Hobbs
Like I said, tenths of a nansecond stuff, with a lot of jitter.
Good marketing, poor engineering. But very few of your customers can tell the difference.
I have a great deal of respect for your engineering capability. It is probably second to none in optics. I was in a different industry. I designed products for the hard disk industry.
I made timing measurements in production test to 100fs. This was essential to meet the accuracy and linearity requirements needed. I was the only person in the industry who could do this. I made millions.
There is a big difference between 100fs risetime and several tens of picoseconds of rms jitter. You should make some tutorials to make this clear to people. You have posted a number of simple equations that describe this.
I chide Larkin on his "picosecond electronics". Do you accept his claims?
I thought not.
SPICE doesn't "fail", the crappy model failed.
"This is especially true if you invoke any [discrete] MOSFET models."
Chip foundry models are superb, and have never failed me. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Thinking outside the box... producing elegant solutions.
"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie
Emendment: LTspice may lie to you and show an unrealistic speed... unless you understand Spice and set the control parameters properly, AND select Solver=Alternate.
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Thinking outside the box... producing elegant solutions.
"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie
The NIF timing system had about 2000 endpoints spread around the biggest laser in the world. Jitter across the system was about 3 ps RMS, or maybe it would have been better if we'd had better oscilloscopes.
We could do better today.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
You really shouldn't let your temper lead you into putting words in people' s mouths.
I have a few of JL's products in my lab. My favourite is the P400 digital d elay generator, which I use a fair amount--it's my go-to pulse generator fo r everything. It's similar to an SRS delay generator I used to have except that its jitter is a good 30 dB less (~5 ps vs ~200 ps). That sort of impro vement doesn't happen by accident.
You claim hundreds-of-femtoseconds jitter numbers for hard disks in 1970. E ven if that were so, that's "sub-picosecond" and not "femtosecond".
However the state of the art in hard drives in 1970 was nowhere near that j itter level. The 1973 IBM "Winchester" drive had a data transfer rate of le ss than 1 Mb/s. Sub-picosecond jitter? Really? Like 120-odd dB down?
I seriously doubt that available test equipment could have made that measur ement, even if by some miracle it was that good.
How did you measure it?
Cheers
Phil Hobbs
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