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4066 bandwidth up to almost 100MHz?

Discussion in 'Electronic Design' started by Deefoo, Jun 2, 2006.

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  1. Deefoo

    Deefoo Guest

    I want to make a simple numerically-controlled attenuator for a 6Vtt signal
    with a bandwidth of 20MHz. Looking at analog switches I was wondering if I
    could simply use a classic 4066 for this task. Philips state an on-state
    frequency response of 90MHz for their HEF4066B but they don't show any
    graphs. Would this work? They sure are cheap compared to other switches.

    Thanks,
    --DF
     
  2. Deefoo wrote...
    I prefer 74hc4053 which allow for making RF attenuators with T-style
    switching. The concern is not only with bandwidth, but feedthough.
     
  3. Deefoo

    Deefoo Guest

    I am not sure I am getting your drift. Do you mean bypassing or not the
    T-network? Then why not a PI-network? Or do you have something else in mind?

    Thanks,
    --DF
     
  4. Jim Thompson

    Jim Thompson Guest

    Win, What off-the-shelf device would you use to multiplex two video
    signals, both have the same sync, and I want to switch frame-by-frame?

    ...Jim Thompson
     
  5. Joerg

    Joerg Guest

    Hello Jim,
    I used to do that with the FET quad array SD5400 but that seems to have
    fallen from grace by now.

    Check out the THS73xx series, mainly the THS7313. Has a 2:1 input mux.
    Guess you don't need three channels but for a little over a buck, why not?

    I don't know if the mux can be switched fast enough via I2C to do it in
    one V-sync period. The 7313 supports the 400kbps mode. Supposedly works
    in I2C high speed (3.4Mbps) but AFAIK that's not guaranteed.
     
  6. Joerg

    Joerg Guest

    Forgot to say: These are from Texas Instruments.
     
  7. Jim Thompson

    Jim Thompson Guest

    I saw those in the latest Electronic Design.
    I may just do a "Joerg" and roll my own with discrete transistors.

    Thinking back to the '60's I did an ultra-fast sample-and-hold with a
    ECL-based tri-stateable unity-gain amplifier (my patent 3,643,110).

    IIRC I could do sub-microsecond switching.

    ...Jim Thompson
     
  8. Joerg

    Joerg Guest

    Hello Jim,
    When it has to be blazingly fast you can do the diode quad and toroid.
    The first time I did that was for my final project back at the
    university. I needed three samplers to hit the sweet spots on a CCD
    readout register. The sampling window had to be 15nsec and you couldn't
    be off more than a couple nsec in timing, and absolutely no jitter. IIRC
    I used 74AS logic as a drive, plus "analog slope enhancers". The toroids
    were, of course, hand wound. Didn't want to wait for a Mini Circuits
    order and wanted to stay within budget. The folks at that institute were
    a bit baffled when I asked for the budget the project would have. Guess
    nobody ever did that before. Got into trouble anyway because I spent
    half that budget on phone calls and telex charges (remember those?) just
    to find all the parts I needed. But, I stayed about a hundred under the
    grand total.
     
  9. Jim Thompson wrote...
    Don't know of a way to do it with one IC. But you know about
    the several nice miniDIP sync-detector chips. The ones I've
    used are spot on for timing. You could drive a flipflop with
    the sync to get a select signal. I'd buffer the video first
    to lower the signal impedance, and use a 74hc4053 to make the
    signal selection, with a G=2 follower amp after, plus a 75R
    resistor for the video out. You may need to have capacitive
    coupling and black-level restoration in the mix, but this can
    be done with the unused 4053 sections, using a set of timing
    pulses derived from the sync chip. I don't recall the exact
    details just now, but my old design drawings are in a folder.
     
  10. Jim Thompson

    Jim Thompson Guest

    I have a whole library of DC restoration schemes :)

    I just thought there might be a fast multiplexor out there that I'm
    not aware of... I haven't done video, even for my own G-jobs, for
    close to 20 years.

    ...Jim Thompson
     
  11. Joerg

    Joerg Guest

    Hello Jim,
    This here paramator indexor has multiplexors:
    http://para.maxim-ic.com/cache/en/results/5148.html

    For a one-up project it may be ok. Else you'd have to find out whether
    it's available in qties and for how long. The latter can make for a
    white knuckle ride.
     
  12. Kevin White

    Kevin White Guest

    Pericom has some good multiplexers for video switching - e.g. P15V331Q.

    They also look useful for other things than video as they have have
    fast turn-on/turn-off times and good capacitance to ground parameters,
    most other fast multiplexers have horrendous capacitance to ground -
    presumably because they use large devices to get the on-resistance low.
    I was recently looking for something along the lines of the HC4053 but
    with fast switching times and this was the closest I could find - it
    does only a limited input voltage range though as it is intended for
    video.

    It is available from Digikey although their search engine often cannot
    find it!!!
    (PI5V331Q-ND)

    I find the classic 4016/4066 is inconvenient to use because it does not
    have level shifters on the logic control lines although for video it
    would be OK because of the limited voltage excursion of video (0-1V).

    cheers

    Kevin
     
  13. The TSH94 video amp will do wired OR. 200nS switch speed.
    john
     
  14. Jim Thompson wrote...
    There are a variety of switch-amplifier combinations, as others
    have said, but I like the hc4053 with a roll-your-own amplifier.
    It's hard to find a faster, lower-capacitance switch, certainly
    not a cheaper, easier-to-get one! It fills the bill for video.
     
  15. Fred Bloggs

    Fred Bloggs Guest

    It must have lousy distortion specs or something if the specialized
    video muxes exist.
     
  16. Jim Thompson

    Jim Thompson Guest

    That looks good. Thanks, John!

    ...Jim Thompson
     
  17. http://www.national.com/pf/LM/LM1881.html
    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  18. Almost anything would do, as long as it is glitch free after the
    syncs, a couple of anything from maxim's stable would be OK, as long
    as the diff gain/phase specs are ok
    Switching video in analogue is dying out
    Personally I'm glad to see the end of PAL/NTSC based equipment, a pain
    in the arse in post production, great for transmission though, well
    thought out, by the time they got PAL working


    martin
     
  19. [...]
    Yes. A lot of tasty digital kit is now available for the high quality studio
    end.
    I must mention, that at the pleb end, i.e. the burgeoning UK video security
    industry. It still relies near totally on analogue composite PAL. Indeed,
    it's difficult to buy a (good!) security cam that offers digital out.
    Stick a PAL cam on a pole, send the 6MHz balanced/unbalanced off for
    monitoring and the car park riff-raff are still clearly identifiable.
    Digitise and compress it a little and you're left with a nice pretty
    picture but near useless for the intended purpose.
    (I'm biased. I earn money from designing analogue matrix routers :).
    john
     
  20. Hal Murray

    Hal Murray Guest

    Does the I2C command have to be fast, or just the last clock happen
    at the right time?
     
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