Is CGA 'about' the same as RGB ? Is NTSC 'about' the same as composite ?
Is there an IC that converts CGA to composite video ?

 

The answers to your questions on the first line are no and no
The answer to the second line is maybe but I have never heard of it. There might be a collection of chips called a display controller that will do it. Maybe based on a Motorola 6845

FWIW -- CGA is a display format in terms of number of pixels horizontally and vertically (320 x 200 IIRC). RGB is a color model.
NTSC is a North American video standard., This is an RF signal in the VHF or UHF bands. Composite video is what you get after demodulating an RF television signal (NTSC) for just the video information. It will usually be standard definition at 480i or 576i. There is no audio.

https://en.wikipedia.org/wiki/Color_Graphics_Adapter
https://en.wikipedia.org/wiki/RGB_color_model
https://en.wikipedia.org/wiki/NTSC
https://en.wikipedia.org/wiki/Composite_video

I think you could have answered your own question by the diligent application of google searches. Maybe it was just easier to ask and have me do it.

 

Is CGA 'about' the same as RGB ? Is NTSC 'about' the same as composite ?
Is there an IC that converts CGA to composite video ?

Sort of. Same for VGA. CGA and VGA are specific versions of RGB.

Yes, but there are several forms of composite such a PAL.

I assume that there is a part that does most of the job. I think better would be to buy a product that already does this. There are lots of them. I am guessing that a typical VGA converter will also do CGA but that would need to be verified.

A quick search finds some as low as $20:
http://www.mycablemart.com/store/cart.php?m=product_detail&p=5658&gclid=CNLI_oDdutACFdgGgQodJ_INhg
It appears to be the best bang for the buck for a complete unit.

 

Is CGA 'about' the same as RGB ? Is NTSC 'about' the same as composite ?
Is there an IC that converts CGA to composite video ?

No need for an IC. I have a circuit that uses one transistor.
I have to dig it up for you.

 

Thanks, gentlemen.
RichardO : Good explanation;
CGA a sort of RGB. Good.
Composite can be in PAL, NTSC, SECAM... Good.

MrChips :
I would appreciate sharing the schematic. My RF spectrum analyzer has a CRT monochrome display but the unit has an external CGA DB-9 output and perhaps I can transplant a cheap LCD NTSC composite video display of automotive-entertainment type to replace the CRT display by internal hook-up and conversion.

PB:
By doing a search is how I got the confusion :

 

Ok, a bit more than one transistor.

 

Wonderful, MrChips. Thank you.
Can be built very compact to be shoehorned-in even when there will be lots of room after disemboweling the CRT.

Now will start the hunt for a 4:3 - 7 inch diagonal LCD module that will accept composite... if not a headrest monitor from a pawn shop

 

BTW, this is not my circuit and I have never tested it. I found in along my travels many moons ago.
I built and used a similar circuit but it was for a monochrome monitor only.

 

If does not test good, no problem. Just found the AD724 does it. Thanks.

 

The circuit I gave you outputs monochrome only. The AD724 does the proper job if you want color.