On 16 Aug 2003 at 16:35, Byron A Jeff wrote:
> I need an 6x2 baseband video / stereo audio switcher with triple switch
> ability: IR, RS232, and manual.
>
> There seems to be three ways of doing this:
>
> 1) Use the integrated Maxim style cross switch. Personally I'm leery of such
>    products because of the great variability of price, availability, and
>    packaging. Digikey seem to carry the MAX4215 8x1, but there's a min buy
>    of 100 units, and they are currently out of stock.

This is the best way to do it. Since you don't need a lot of parts, just get
samples from Maxim.

> 2) Relays. One possibility is simply to have 36 reed relays on a board. BG
>    Micro is selling 5V SPST reed relays 3 for a buck. But that's a whole lot
>    of real estate to cover.

Remember this is video. You're going to have a hard time maintaining a
nice signal path with that setup.

> 3) Transistor switching where you substitute a NPN transistor for the relay.
>    Zoomkat has a sample app here:
>
>    http://www.geocities.com/zoomkat/ppswitcher3.htm
>
>    The packaging leaves something to be desired.

Didn't look, but somehow I feel you'll add DC or series impedence.

> So I was wondering if an opamp could be configured as a switch. A quad opamp
> package could route 4 signals. However after scrounging around Google for
> a couple of days, I couldn't find anything definitive. In fact many pages
> discussed using a analog switch to bybass an opamp.

There are certainly opamps that can be used for video, but your whole
circuit needs to be well though out. Remember this is DC to 6 MHz, and
phase shift is absolutely critical if you like color accuracy.

> Any suggestions? The fall TV season is upon me!

Maxim has done the hard work for you already.

Cheers,

Bob

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