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Inexpensive Dual NPN Transistor in Metal Can Package?
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Chris56000:
Hi!

I'd like to try experimenting with the circuit for the Audio Sweep Generator here:–

https://www.americanradiohistory.com/Archive-Poptronics/70s/1973/Poptronics-1973-10.pdf

. . .but I'm having trouble finding a dual NPN TO–78 transistor that doesn't cost an arm and a leg–can anybody recommend one?

Chris Williams
Wolfgang:
Some question:

- Whats your budget ?
- an alternative to a metal can dual transistor could be a transistor array IC.
Chris56000:
Hi!

Ideally one figure – < £7.50 (or less!) Including P & P.

The original article didn't discuss the theoretlcal aspects of the circuit, so not being exactly sure why one was specified, I can't think up substitutes!

Chris Williams

Would two of the transistors from a '3046 do? There was no pcb artwork given as the article said "these can be bought from. . .", so if a '3046 would do, I'd be more than happy to make up a design to use one in that section of circuit, or even wire it on "proto–board" to try it – when a home constructor calls for an odd transistor type, there's obviously a reason for it!
Wolfgang:
I looked at your circuit, and I am sure that transistor arrays would be suitable.
Examples: CA3046, TPQ2222, CA3018 all on eBay.
soldar:
Also you can probably just take a couple of paired transistors (with very close gain and other characteristics) and join them thermally with paste so they are thermally coupled.
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