A Curve Tracer is a Device which will show the Voltage / Current dependency of an electronic part. It is therefore suiteable to discover characteristics of electronic parts - and to quickly check if they are o.k. - or if the smoke left aleady. This Project is useful for educational reasons, as it is simple but clever.

Fig.1 .:. Homebrew Curve Tracer - a very handy Tool !

All we need is an Oscilloscope with an x and an y input. (This feature is available in almost every Oscilloscope.) The horizontal axis represents the Voltage (x) whilst the vertical axis (y) represents the Current.




Fig.2 .:. Schematics


The minimum Configuration uses only three parts :

• A Transformer
• A Current Limit Resistor (R1)
• A Current Sense Resistor (R2)
(There is a 330pF Capacitor to reduce noise, parallel R2)

We used a Transformer with 15V which will deliver 30Vp or 60Vpp. In order to
limit the current to 10mA, R1 was chosen to be 3kΩ. R2 was chosen to be 10Ω.

A more luxurious Version may use a Switch to select different maximum Currents.




Fig.3 .:. Built 'on the fly'

With this configuration, the following curves have been measured :
(Set the Y-Channel to 'inverting')




Fig.4 .:. No D.U.T. - High-Z





Fig.5 .:. A Resistor of 2.5 kΩ - 5V/Div : 2mA/Div





Fig.6 .:. 1N4007 Diode





Fig.7 .:. A Zener Diode of 18 V





Fig.8 .:. A Zener Diode of 9.1 V - the other way





Fig.9 .:. Two Diodes 1N4007 - antiparallel





Fig.10 .:. Two Diodes 1N5711 (Schottky) - antiparallel





Fig.11 .:. Two Diodes 5082-2835 (Schottky) - antiparallel





Fig.12 .:. A Capacitor - C = 1 µF





Fig.13 .:. A Resistor 2.5 kΩ in series with a Capacitor C = 1 µF





Fig.14 .:. A Varistor, EPCOS S05K25

Curve Tracer Project .:. Part 2

This Section will add Gate / Base Drive in order to examine Transistors.

Click here to go to the advanced Curve Tracer Website.

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