Use AC coupling.
BTW, the use of a series resistor is discussed in Howard Johnson, "A Handbook Of Black Magic," in numerous places. For example, see Figure 3.12 on page 105:
and
This book has a lot of useful information that is hard to find elsewhere. It is not clear why it is so badly maligned by some.
For narrowish-band RF, that can work OK. For fast pulse stuff with lots of drive, the DC-coupled version can work very well. Otherwise, a
20k // < 1pF probe such as a P6249 is a big win. ("There are more things in photodetection and dynamic range, Horatio, than are dreamt of in your philosophy.") ;)Just today I used it with my TDS 694C to track down a 2-GHz birdie in a cascode front end. (Turned out to be ambient RF rather than a parasitic.)
You seem to be trying to use HoJo to teach his grandmother to suck eggs. ;) I've been doing stuff like that since the very early '80s.
As JL has well said, "It's half nonsense and half good stuff. If you know enough to tell the difference, you don't need the book." He and I have had a few fun go-rounds about that in this very boutique over the last decade or so. YCLIU.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Vishay shows bandwidths well into the GHz.
Why would AC coupling make any difference.
How can you beat the dynamic range of a resistor.
A good spectrum analyzer is far better for EMI. You can see much lower amplitude signals for one.
Nonsense statement.
Got you beat. Late '60s, early '70s.
There seems to be a lot more good stuff than you admit.
I interviewed with Tek back in 1987 when I was finishing grad school, having been recruited by their guy at Stanford, Jeff Goll. (Jeff was very smart and also a really good guy, which was part of the draw.)
They wanted me to help make electrooptical digitizers for what were then ultrafast scopes (> 2 Gs/s), which would have been fun. It was a thrill meeting some of their remaining electronics gurus--I've long admired folks like Battjes, Getreu, Hollister, Traa, Gilbert, and so on.
One of them, whose name I forget, gave me a circuit to analyze, which made no sense to me. I looked at the DC characteristics, which made no sense, then at the AC characteristics. It turned out to be an ancient relaxation oscillator thing based on super-leaky germanium PNPs, so that none of the bias currents were going in the right direction. Of course nothing was said about the transistors involved...they didn't expect interviewees to have seen transistors that bad, they just wanted to see how they approached the problem. (I didn't figure it out either, but I had a good try.)
I liked them, and apparently they liked me too, at least enough to mke me a job offer. Thing was, I had a wife and baby to support, and Tek never had enough revenue per employee to be able to pay their people properly. A pity.
I mostly had a good time at IBM though. ;)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Hojo? Is that you? Why the alias?
Like what?
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
General Electric actually sold some solid state AM table radios that were b uilt without bias resistors. It was real fun finding a replacement transist or when one failed. By then, they had either run out of floor sweepings, or sold them all to Poly Packs. Can you imagine some poor tech with no design experience trying to calculate the proper bias? Even the audio output was a TO66 150 PNP The transistors didn't cross to anything else, ad appeared t o be rejects from Aerospace contracts.
Phil Hobbs wrote
Yes; exactly. The main reason I want this "1pF" probe is for looking at STM 32F ARM crystal oscillators, especially the 32kHz one on which the bias resistor is 18M (so on that one I actually need an AC coupled probe also).
Phil Hobbs wrote
This is the best I can see at the moment
unless I go for some US deals which tend to be cheaper but with a huge delivery charge.
Most are clearly in a poor condition.
A lot of the ones I see are incomplete kits. One clearly must get the
10x tip for example.snipped-for-privacy@highlandsniptechnology.com wrote
Lots of dodgy stuff went on during that time - basically to do with collaboration by the natives, which is embarrassing. Since the islands are dominated by a small number of "ruling families", it implicates many people currently living.
One could however argue that every occupied population collaborates, because it is the best option.
High-frequency FET probes have nonzero DC loading. IIRC the P6201 is
100k and the P2349 is 20k. So you'll still need a series cap.Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Yeah, you need a bit of patience. I've been collecting eBay test equipment for a dozen years or so.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
I wonder what is missing in that kit? The seller is not saying; only saying you get what's in the photos ;)
I bought this one
There is a lot of incomplete kits, as well as some with lots of extras.
Also, curiously, there are lots around the 150 area and lots around the 650 area. Strange as there don't appear to be two different versions of the probe. And all will be ~30 years old now.
Compare those photos with
YCLIU
I've read the book. Seems like you haven't.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
It's missing the 013-0135-00 probe hook and the ground lead. However, all the probe points seem to be intact, and they've even included a spare, which can come in very handy.
is a much cheaper listing that appears to have everything.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
I friend joined IBM the same time as I did, same position, same department. After five or six years, he moved to Tek at a somewhat lower salary. After five years, or so, he was making about 60% of what I was. Tek paid really poorly in the '70s and '80s. Beaverton wasn't exactly a cheap place to live, either.
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