Transistor Tester

Jig used for matching discrete transistors. Sets up a constant current in the transistor under test, with 5uA and 500uA selectable by a DIP switch. Handles both npn and pnp.

I used an 8pin DIP socket to plug the DUT's in to. The red traces on the PCB are bare wires on the top side looped so they are easy to grab for measuring Vbe

Operation:

• Protect from wind currents and drafts (that can cause temperature changes
• Switch to 5uA current. Attach DVM probes to appropriate connection points for measuring Vbe
• Plug DUT into appropriate pins on socket. Use pliers not your hands to handle the DUT
• Wait until reading settles (~45 sec). Read and record Vbe to 4 digits
• Switch to 500uA and repeat

I have a piece of paper that I taped a piece of black electrical tape to, sticky side up, that I stick the transistors to and record the Vbe reading for. That way you can save and compare the Vbe's. It's fairly easy to get transistors to match within a 0.5 milliVolt if they are from the same lot.

Status

PCB built and stuffed PCB tested and working

Transistor Tester schematic

Transistor Tester PCB 2x size