VBE Matching

This is a small PCB project based on Ray Wilson’s Music From Outer Space VBE Matching schematics.

At some point I got tired recreating this useful tool on a bread board every time I need to match transistors for VCO or VCF expo converters. It helps to measure Vbe for PNP and NPN transistors using your high precision bench multimeter.


Eagle .sch/.brd files are available here.

Schematics in PDF format.


Most of the components are very generic. I’ve used the following parts:

Digikey part LM4040DIZ-10.0.

The NPN/PNP switch is SSA12 from TE Connectivity, DigiKey part 450-1602-ND.

For EBCE connector you can use any DIP8 socket, however I used 2 x 4pin headers with golden connectors from unknown source.

11 thoughts on “VBE Matching

  1. I see that below top-right IC in the schematic are two resistors but in the photo there are some capacitor. Why is that? I should do version from eagle file?
    And can I freely use TL081 instead of TL071?

  2. so i’m still not clear on this afterall. i’m seeing an ouput of 5v with no transistor in.the i’m seeing 0.5v with a transistor in circuit. then you can sort of watch it rise bit by bit and stabilize from .5113 to .5575. nothing is buring seems to be working. i’m just not sure what i’m supposed to be looking for??? help.

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