"Tim Williams" writes:
>
>>
>> How do they, like, Tek themselves for instance, do it in scopes? Well,
>> when they made good analog stuff anyway... The, what, 2465 is it, does 4
>> channels out to 500MHz or something like that, no sampling of any sort
>> needed. Now, I know part of that is tube design, but they still need to
>> make voltage. How much, how, and with what?
>
>There is an chapter on the development history of Tektronix vertical
>amplifiers in the book "Analog Circuit Design: Art, Science and
>Personalities" edited by Jim Williams.
>
>
>
>You might find it interesting - the 7104 went up to 1GHz, still the
>fastest analog scope made AFIAK. It uses a circuit configuration they
>invented called an "Ft doubler" :)
IIRC Iwatsu has analog scopes that go beyond 1GHz.
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I've gotta wonder, do you get into troubles when swinging the electron beam that fast? Does it just spray out wherever you point it, regardless of the rate? The bend in the beam isn't exactly negligible, especially as the beam isn't going nearly the speed of light, and it has some mass.
I wonder if you can hook up the CRT to a waveguide and get interesting TWT style responses from it. Not at much power of course.
Tim
-- Deep Fryer: A very philosophical monk. Website @
I remember CRT's with multiple section deflection plates connected by an internal delay line so the "wave" over the deflection plates matched the electron beam speed.
This was called "distributed deflection". It was used, IIRC, as far back as some
5xx series 'scopes. And in any 'scope Tek made that worked over 100MHz, including the portable 454. If you looked at the schematic for the vertical deflection system, it had a wizard on a skateboard (or some such thing).
I don't know if I ever saw a "manual" of high-speed design such as what someone else described. Perhaps that was assembled after I left Tek. It would have been based on the "AFTR" (Amplifier Frequency and Transient Response) course, which was really a wonderful class. I took it when Carl Battjes taught it, and again with Bruce Hofer. They were excellent and inspiring teachers, though they had somewhat different styles. I've found only some of the concepts taught in the course in "outside" references since that time.
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Ft doublers and such were really the province of the integrated circuit. Of course, Tek had serious difficulties in the early days of their IC manufacturing. For example, when the 465 was originally designed, it had an IC-based vertical deflection amplifier (which, IIRC, had an Ft doubler). As shipping date approached, they found they couldn't produce enough for it and the 7000 series, which needed the same IC. Jim Woo - another great Tek engineer - took just one weekend to design a discrete version which was used through the entire life of the original 465 (including B, but not the M version). Some years after he had designed this amplifier, I asked him a question about the particular coupling method he had used in connecting the amplifier to the deflection plates. This is a critical area, one of the fundamental limits to the bandwidth of a 'scope - due to the resonant combination of the lead inductance with the capacitance between the plates. It turns out that it hadn't been done by him, but someone in production engineering! He'd never noticed it. Of course, distributed deflection overcomes this limitation, becoming a transmission line (complete with termination resistors, which aren't shown in the drawing above).
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