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MATCH: Direct-mount transistor matching module PCB (4HP)
MATCH: Direct-mount transistor matching module PCB (4HP)
York Modular

MATCH: Direct-mount transistor matching module PCB (4HP)

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First of all, you're probably wondering what a direct mount module is - easy, it's a panel-sized PCB which you attach directly to your rack. Maybe not so good for performance use, but for tinkering around it's perfect.

This is a board which will hopefully make the act of matching transistors rather less tiresome - it was born out of the need to get matched pairs of transistors for some forthcoming modules which require them.

I can't claim that I came up with the circuit - it was designed by Ian Fritz and has been floating around the internet for a good few years now. His original article can be found here (slightly technical) and there's a slightly less technical over view here. Needless to say, for a circuit which uses a handful of passives, it is both simple and very effective.

There's provision for matching both PNP and NPN transistors, and each has a couple of test points to which you can connect a DVM or similar to measure the differential voltage (or not) of a transistor pair. This is a simple build, and the only remotely exotic components required are two pairs of matched 100k resistors (I used 0.1% tolerance resistors in my build because there's no kill like overkill) otherwise it's stuff you'd probably find lurking in your bits box.

BOM, schematic and Gerber files can be found here: https://github.com/yorkmodular/transistor-matcher-directmount

The PCB and mounting hardware are supplied - it is up to you to source components and perform the build.