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Op-amps suitable for video
MUFF WIGGLER Forum Index -> Video Synthesis  
Author Op-amps suitable for video

alphabetter

Hi Folks,

I've been doing a lot of work with circuit-bent video mixers which is all documented here:
http://lushprojects.com/videobend/

Recently I've been thinking about developing something that is a bit more predictable and structured along the lines of a modular video synth. I would probably want to mix-and-match modular components along with my circuit-bent projects.

Anyway, I wondered if you had any thoughts on the best general-purpose Op-Amps to use for video work. I was thinking about the MCP662.

Iain


lizlarsen

A lot depends on if you're okay with surface-mount parts, since a lot of video ICs aren't available in DIP packages. The AD828 is an easy one to work with, that's available in a DIP package, but expensive (you can always request a few free samples if you don't need a lot.) LM6172 is good too.


daverj

That Microchip op amp isn't as good as the ones Lars mentioned. It's slew rate is only about twice that of the TL072 audio op amp. And it's power supply range is limited.

There are quite a range of video amps these days, but as Lars says, a lot of them are surface mount only.

Each chip company has selection charts where you can narrow down their selection based on various choices. I would suggest ones that run off of +/-5 volts, have slew rates higher than 100V/uS, and for the most part you'll probably want voltage feedback amps. Current feedback amps have their purposes, but most basic amp circuits will use voltage feedback amps.


alphabetter

Thanks good comments. Stupidly I handn't checked the slew rate on the one I mentioned.

No problem with surface-mount as long as it isn't some stupidly small form-factor.

I guess one reason I steer away from comparison tables is that I tend to think that personal recommendations are more likely to give a mainstream option that might have a longer manufacturing life than some new device that never finds a market.


daverj

alphabetter wrote:
No problem with surface-mount as long as it isn't some stupidly small form-factor.


Those are the ones I use. hyper


daverj

Seriously, I'd go to the large analog chip makers sites (National, Maxim, Analog, TI) and look at some of their video application notes. Then look up the amps they use in their examples for video cable drivers and such. Those are the best ones.

If you can handle soldering SOIC, then look at the Maxim MAX4392ESA. It's a low cost basic video op amp. The ones I use maybe cost a bit more and are maybe a bit better, but the largest size they come in is less than 1/2 the size of a SOIC.


lizlarsen

There are also some great app notes out there, like this one, that cover some basic circuits:
http://cds.linear.com/docs/Application%20Note/an57fa.pdf

We use a custom protoboard that allows SOIC chips and thru-hole passives for prototyping that works quite well.


alphabetter

Thanks. More good tips.

SOIC I find reasonable comfortable. I have worked down as small as TQFP but that is getting a little hairy!

That application note looks very interesting Lars.

Wish I had more time......


daverj

That's a pretty good app note, but be aware that it's 17 years old and parts of it were pulled from even older app notes. There are lots of newer chips available since then.


okelk

daverj wrote:
Current feedback amps have their purposes, but most basic amp circuits will use voltage feedback amps.


Would you mind explaining what those purposes are?
I sometimes come across them in schematics, but still don't quite get when and why they are used...

I'm probably going to buy a few MAX4392 for a project...
but I'm still open to suggestion for a poor-man's video op amp...(I'm fine with using a +/-5V supply and everything that is not BGA)

Also, Does anybody have an opinion on the LM359 'norton op amp' for video?
It's a bit unusual...but there are a few application notes full of useful schematics...

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