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DIY Stompboxes => Building your own stompbox => Topic started by: mistahead on August 13, 2013, 08:37:45 PM

Title: ULN2003 Cascader idea
Post by: mistahead on August 13, 2013, 08:37:45 PM
I've was skimming through a catalogue and noticed ULN2003 darlington transistor array IC... and am yet to really study the datasheet, but at glance (or using a similar IC)...

So to prod the proverbial of the collective I'm thinking of using this IC to produce cascaded boosts, switched clipper sections in the cascade, put a tonestack near the end and use the IC for a recovery.

Is that really enough to ask of the circuit though - what else could I push it into doing?
Title: Re: ULN2003 Cascader idea
Post by: R.G. on August 13, 2013, 09:13:38 PM
The biggest problem is that all those darlingtons have their emitters permanently grounded inside the chip.
Title: Re: ULN2003 Cascader idea
Post by: mistahead on August 13, 2013, 09:30:06 PM
Yep, that's a problem.

I need a catalogue with datasheet AR built in - this old school paper without hyperlinks is killing me.
Title: Re: ULN2003 Cascader idea
Post by: PRR on August 13, 2013, 10:44:34 PM
> what else could I push it into doing?

Solenoid valves, servo motors, indicator lamps.....

ULN2003 would not be my go-to for any audio path. (And I _have_ used TIP120 as a mike-amp.)
Title: Re: ULN2003 Cascader idea
Post by: mistahead on August 13, 2013, 10:49:48 PM
I'll just have to keep an eye open for a darlington array that might be more usable as a racked-up ready to cascade IC, in the mean time I'll just get back to looking up MOSFETs on the adjacent page.

I have some "random" PLL chips and timers on the way, maybe I should be looking at comparators instead?  :icon_smile:
Title: Re: ULN2003 Cascader idea
Post by: PRR on August 13, 2013, 10:54:42 PM
Single Darlings are cheap and more versatile than arrays; UNLESS you need seven doing the same thing.

http://zeptobars.ru/en/read/ULN2003-per-element-die-annotation
Title: Re: ULN2003 Cascader idea
Post by: defaced on August 13, 2013, 11:18:08 PM
Quotehttp://zeptobars.ru/en/read/ULN2003-per-element-die-annotation
Thanks for posting that.  Not only is that page interesting, but that site as a whole is pretty cool with alot of good info. 
Title: Re: ULN2003 Cascader idea
Post by: mistahead on August 13, 2013, 11:29:12 PM
Quote from: PRR on August 13, 2013, 10:54:42 PM
Single Darlings are cheap and more versatile than arrays; UNLESS you need seven doing the same thing.

http://zeptobars.ru/en/read/ULN2003-per-element-die-annotation
Agreed - great resource - thank you.

Darlingtons are cheap , and as has come up a couple of times lately - a good application for some of the single BJTs that are a bit off application spec is to pair them up (there was a Rangemaster convo with Smallbear and others on this).

I love using darlington pairs, there is something about watching the effect on the gain numbers or pairing up transistors - 5th gear overdrive circuit uses a darlington building block that I really like (MPSA13 or MPSA18 based, can't recall right now, one isn't a darlington though), something to be said about what can be done with five or eight discreet parts when other applications are using ICs with more "parts" on board than that.

If however I was looking at seven stages, all identical, being manipulated by seven stages of controller with one physical input - yep array looks like the way, otherwise I am getting the message that the limitations don't warrant the approach.  :icon_lol: