# Minimig Video output

Jump to: navigation, search

My suggestion is to add copper traces to allow simple soldering of circuit to enable this.
By not assamble this by default some money can be saved.

A500 & A1000 to TV S-Video input using Analog Devices AD724:
http://eab.abime.net/showthread.php?t=30752

freqmax (070731):
The minimig only have a physical VGA socket for video.

4bit/color resistor ladder D/A:

http://home.hetnet.nl/%7Eweeren001/downloads/minimig1_schematics.pdf Page 3/3

Resistor values 4k, 2k, 1k, 560 ohm. Method1 - Adding resistors:

R=1/(1/4000+1/2000+1/1000+1/560) = 282 ohm
U=3.3 Volt
i=U/(R+75) (impedance of VGA is defined as 75 ohm)
Output voltage max: 75*i = 0,69 Volt.

Method2 - Using Kirchhoff's law:

(3.3/(4000+75)+3.3/(2000+75)+3.3/(1000+75)+3.3/(560+75))*75 = 0,8 V (weird..)

This is all fine provided that impedance is exactly 75 ohm. However reality may not be perfect. So maybe the output should have some circuitry to handle monitors/cables that doesn't follow the 75 ohm impedance strictly?

Also the 560 ohm value seems nonlinear. See also Wikipedia.org Preferred number.

Maybe DVI/HDMI is a useful option? (no need for D/A and plugs directly into lcd-tv)