Controlling High Voltage 7 Segment Display using MAX7219

Hi, anybody had success with MAX7219 high voltage led configuration [http://www.maximintegrated.com/app-notes/index.mvp/id/1196], can suggest transistor models I can use for Q1, Q2 & Q3, I'm planning to drive digits each having segments rated 9V / 30mA.

Please share the experience on this if anybody allready done this it will be a Great help. Thanks.

Wouldn’t the bog-standard BC547 be ok for this? The max. collector current is 100mA and the maximum voltages are more than high enough.

Thanks for the reply, but what about Q2, its a FET ? ... can anybody help me on this..

Looks like a P-Channel MOSFET. I'll bet there's a cheap "standard" one people tend to use for this sort of thing, but I don't have a part number off the top of my head to give you!

EDIT: You could try a parametric search on the component supplier's website of your choice, to find which ones are suited to your requirements :)

BulletMagnet83: Looks like a P-Channel MOSFET. I'll bet there's a cheap "standard" one people tend to use for this sort of thing, but I don't have a part number off the top of my head to give you!

EDIT: You could try a parametric search on the component supplier's website of your choice, to find which ones are suited to your requirements :)

thanks for the info, any possibility of using a digital pot like MCP413 or AD5204, to control the brightness of 7 seg displays by limiting voltage, instead of PWM ?

I'd just do it in software by sending the appropriate commands to the 7219. Why add extra components and complexity if you don't have to? :)

First thanks for the reply, the problem is I find many threads with problematic situations on this, so I decided go in that way... seems much promising. If you know please provide me some more detailed info about configuration of controlling high voltage 7 segment intensity directly with MAX7219.