howard parkin wrote:
Here's the story with the 50ohm output impedance.
The large majority of monitors are 75ohm, whether they are VGA
or BNC. However this interface has been included to specifically
drive a two types of monitor on the market that really are 50ohm.
The D/A converters and amps on this video head are expensive.
In fact they would add about $100 to the price of the board.
Traversal will not be fitting them on the standard board that we sell.
If somebody needs to drive 2048x1536, thay can use the
330Mpixel/s VGA on the other connector. If anybody needs to
drive two 2048x1536 monitors or 2048x1536 at more than 75Hz
frame rate, then Traversal may add the extra components or they
can do it themselves. In this case 50 or 75 ohm resistors will be
fitted as required and the D/A current set resistor modified
accordingly to give the required voltage swing (usually 0.7Vp-p
without syncs).
To avoid any confusion, I will add a comment to the schematic
to indicate that either 50ohm or 75ohm can be fitted.
Sounds good. Issue resolved.
--
JRT
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