Curve tracers

Curve tracing is a classic way to learn more about many electronic components. Curve tracing is essentially a means of making a graph of current (I) versus voltage (V) called an I-V curve, to display the basic characteristics of an electronic device. I-V curves of the components are helpful in understanding their limitations and nonlinear operation. Such curves are also useful in establishing circuit models and for determining bias points, load lines and boundaries of the devices.

Nowadays curve tracing seems to be a somewhat lost art, as many engineers rely only on the curves given by the device manufacturer. As any electronics hobbyist knows, device actions in real life will (often largely) vary from the model that defines its operation. Many electronics struggle with Tracing Curves, whether it be the smooth VI line of a capacitor or the voltage of a collector transistor against the current curve.

AC curve tracing is the most common way to do curve tracing. You need an AC voltage source, a transformer, some resistors and a DC-coupled oscilloscope to measure two terminal devices.

Component Tester – Curve Tracer

Simple Component Tester

How to Use an Oscilloscope and Signal Generator as a Component Tester / Curve Tracer

For effective curve tracing of transistors, a somewhat more complicated testing device is needed. A good transistor tester does the curve tracing with many different base current values.

Here are some project links:

Create Your Own I-V Curve Tracer
In this article I will describe an economical way of obtaining the I-V curves of two- and three-terminal devices, using a PC, an economical USB oscilloscope (Hantek 6022BE), a simple circuit and a bit of Windows software. It’s a project that should appeal to almost anyone involved in electronics.

Simple Curve Tracer Circuit for Resistor, Diode, and Transistor

Building A Curve Tracer

DIY Generic Curve Tracer
Using the on-board Phase Shift Oscillator to provide the test signal, passive and active parts can be tested.

Simple but effective Transistor Curve Tracer circuit.
This curve-tracer uses only 6 transistors and produces a beautiful curve display on an oscilloscope in X-Y mode

Transistor Curve Tracer
For a PNP or NPN transistor it plots Vce (the voltage between the collector and emitter) versus the current flowing into the collector. A line is drawn for each different base current – e.g. 0uA, 50uA, 100uA, etc. For a MOSFET it plots Vds (the voltage between the drain and source) versus the current flowing into the drain. A line is drawn for each different gate voltage – 0V, 1V, 2V, etc.


Be the first to post a comment.

Leave a Comment

Your email address will not be published. Required fields are marked *