Simple Curve Tracer Circuit for Resistor, Diode, and Transistor

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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. Those curves give one an intuitive view of how a circuit-based system works.
An analytical approach may include plugging distinct voltage and current values into a mathematical formula and graphing the effects, usually with the voltage-defined x-axis and the currently represented y-axis.

As any electronics hobbyist knows, device actions in real life will (often largely) vary from the model that defines its operation. Here we will use a circuit to add discrete voltage changes to the part whose VI curve we want to draw and then use an Oscilloscope to display the effects.

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Hardware Components

The following components are required to make Curve Tracer Circuit

S.no	Component	Value	Qty
1.	Resistors	1K, 10K, 10M, Test Resistor ohms	1, 1, 1, 1
2.	Ceramic Capacitors	10uF, 10nF, 100nF	1, 1, 1
3.	Electrolytic Capacitor	10uF	2
4.	IC	NE555 Timer	1
5.	Op-Amp IC	LM358	1
6.	Transistor	BC557	1
7.	Power Supply	–	1

NE555 IC Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer

LM358 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of LM358

Curve Tracer Circuit

Working Explanation

The circuit used here is a simple variant of the standard 555-astable circuit, which will act as a Sawtooth waveform generator. Normally the timing resistor is supplied through a resistor connected to the power supply, but here it is connected to a constant current source. This results in a steady current for the collector. The charging of a condenser results in a linear ramp waveform using a constant current.

This design derives the output directly from the condenser output and not from pin 3, which gives here small negative pulses.