PNP drivers
Hello all I am posting this message to see if anyone knows of an alternative to the ULN2803 (type) drivers? I am MIDIfying a large residence organ and although the ULN type drivers work very well, the power supply to the organ has to be reversed so its not as perfect as it could be. It is possible to build a circuit with lots of PNP transistors but an array would be more compact. I have read posts that PNP drivers are slower than NPN, anyone got any ideas? Thanks Mark

Regarding alternative to the ULN2803
Hi, I will research regarding alternative to the ULN2803 at work tomorrow. I have built a PNP transistor board for a midi piano so it needed to be very fast. You may have seen my posting for my midi Pianola on iMOD, but if you interested this is the link to the article. http://homepage.ntlworld.com/phil.radford/index.html Anyway if you’re interested you are welcome to a copy of the schematics and board layout if it helps.

Hello, For high-side switching, you could use the UDN2981A from Allegro Microsystems or one of the TD62783 series chips from Toshiba. These are both 8-channel open-collector drivers in 18-pin packages, near enough identical in rating and operation to the ULN2803, but using PNP transistors internally to give a pull-up rather than pull-down output. Unfortunately, they're not quite pin-compatible with the ULN2803 (two pin connections have to be swapped), but they should be as easy to use as the ULNs. There's no need for concern over the speed of PNP transistors compared to NPN - the difference will only be a few microseconds which shouldn't affect your music in any noticeable way! Regards, John.

Thanks
Chaps Thats EXACTLY what I needed to know.