Mini Curve Tracer!
Updated 1/5/2026
Finished Curve tracer measuring a BJT.
I've always loved the idea of being able to visualize the differences between components by looking at
a generated shape. This device is a classic transistor curve tracer, which plots the current vs voltage plot
of whatever transistor is inserted into the ZIF connector. It then applies various base currents or gate voltages
and draws a new curve on the same plot.
The final construction of this project is on a stiff piece of stripboard, an Arduino pro mega is the brains
of the device and allows for a full touchscreen interface! This curve tracer allows for BJTs, Mosfets, and J-Fets.
The device is measured as soon as it's inserted, detecting a voltage rise across the current sensing resistor.
The settings for the difference between control voltage steps can be dialed in - in a menu.
This device is hugely inspired by this Instructables! Although I tried to do almost all the design work myself.
This is a typical NPN transistor curve. This device has become part of my common desk assortment, its amazing in finding breakdown voltages, matching transistors, checking HFE, checking when a transistor becomes saturates, and differentiating aliexpress fakes from real transistors! I use it a ton!
Here's an oscilloscope reading of the "step" voltages applied to the base/gate of the transistor and the accompanying voltage sweep across the collector-emitter/drain-source. Each step represents one curve on screen, while this whole image represents an entire plot of the curve tracer.