I looked at the data sheet you mentioned, and it showed the LEDs coming out
with both leads. I had one display that had only the anode brought out, but
it only drew about 40 ma, so it was easy to use a single transistor to
drive the backlight form 5V.

At 02:33 AM 3/26/2004 +0100, you wrote:
> > Note that you have access to both the anode and
> > cathode of the backlight, so you can connect the anode to the +9 volts,
> > then connect the cathode via a resistor to the FET. You don't have to drive
> > the anode of the LED, trying to switch 9 volts. That's why you need to use
> > 2 transistors in your circuit.
>
>I'll try to use the FET. The problem is I'm not sure if the cathode of the LED
>is connected to the LCD's VSS.
>
>I recently used 1 NPN transistor to do it this way (but with other display).
>When I plugged it everything started getting hot. After some testing I
>found that
>VSS and the LED's cathode were connected in the LCD's pcb. A *little* fact the
>datasheets didn't mention.
>
>
>Thanks for the responses!
>
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Larry Bradley
Orleans (Ottawa), Ontario, CANADA

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