ULN2003 audio amp. - UK Vintage Radio Repair and Restoration Discussion Forum

G6Tanuki · 18th Feb 2023, 8:34 pm

I've got a bunch of ULN2003 ICs here, and thought I should use them 'experimentially' - meaning I would be happyb if a few of them were to be killed 'in the interests of Science!'

They're seven Darlington transistor-stages in a DIL package.

https://en.wikipedia.org/wiki/ULN2003A

With clamp-diodes to some putative common-ground.

I kludged-up a circuit which left the common-diode ground floating, and strapped the transistors in two-pairs-of-three parallel.

Then wired then resulant 'composite transistors' into a version of the classic transformer-driven/loaded Class-B-with-a-touch-of-base-bias-to-avoid-crossover-distortion circuit where we would have in the sixties used OC72 or OC81 transistors.

The results are impressive: I reckon to be getting a Watt or more when fed from 15V and it doesn't sound bad.

Has anyone else played with these? My next adventure will to be investigating if they work as RF amplifiers on 1.8MHz.

Cruisin Marine · 18th Feb 2023, 9:22 pm

I have no personal experience of them, but they would be great for many uses- more gain than you can throw a concrete slab at!

18th Feb 2023, 8:34 pm	#1
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,996	ULN2003 audio amp. I've got a bunch of ULN2003 ICs here, and thought I should use them 'experimentially' - meaning I would be happyb if a few of them were to be killed 'in the interests of Science!' They're seven Darlington transistor-stages in a DIL package. https://en.wikipedia.org/wiki/ULN2003A With clamp-diodes to some putative common-ground. I kludged-up a circuit which left the common-diode ground floating, and strapped the transistors in two-pairs-of-three parallel. Then wired then resulant 'composite transistors' into a version of the classic transformer-driven/loaded Class-B-with-a-touch-of-base-bias-to-avoid-crossover-distortion circuit where we would have in the sixties used OC72 or OC81 transistors. The results are impressive: I reckon to be getting a Watt or more when fed from 15V and it doesn't sound bad. Has anyone else played with these? My next adventure will to be investigating if they work as RF amplifiers on 1.8MHz. __________________ I'm the Operator of my Pocket Calculator. -Kraftwerk.

18th Feb 2023, 9:22 pm	#2
Cruisin Marine Heptode Join Date: Jul 2018 Location: Worthing, West Sussex, UK. Posts: 989	Re: ULN2003 audio amp. I have no personal experience of them, but they would be great for many uses- more gain than you can throw a concrete slab at! __________________ "Behind every crowd, there's a silver Moonshine"