4066 bandwidth up to almost 100MHz?

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

Reply to
Deefoo
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I prefer 74hc4053 which allow for making RF attenuators with T-style switching. The concern is not only with bandwidth, but feedthough.

--
 Thanks,
    - Win
Reply to
Winfield Hill

signal

I

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

Reply to
Deefoo

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

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

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.

--
Regards, Joerg

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Reply to
Joerg

Forgot to say: These are from Texas Instruments.

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

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

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

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.

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Regards, Joerg

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Reply to
Joerg

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.

--
 Thanks,
    - Win
Reply to
Winfield Hill

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

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Hello Jim,

This here paramator indexor has multiplexors:

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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.

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

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

Reply to
Kevin White

The TSH94 video amp will do wired OR. 200nS switch speed. john

Reply to
John Jardine.

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.

--
 Thanks,
    - Win
Reply to
Winfield Hill

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

Reply to
Fred Bloggs

[snip]

That looks good. Thanks, John!

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

formatting link

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Reply to
Michael A. Terrell

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

Reply to
martin griffith

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

Reply to
John Jardine.

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

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Reply to
Hal Murray

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