Keithley SMUs emulate classic curve tracers with new software

By Gina Roos, editor-in-chief

Tektronix brings many of the key features loved in classic curve tracers to Keithley SourceMeter source measure units (SMUs) with the release of its Keithley I-V Tracer software. Tektronix introduced the industry’s first curve tracer in 1955 to display characteristic curves for vacuum tubes. This was followed by models for testing transistors, diodes, and other solid-state devices. Production of the curve tracers stopped in the mid-1980s.

Approximating a power supply and an oscilloscope packaged in the same box, curve tracers source voltage while plotting voltage versus current, said Joseph Gorley, product manager at Keithley. Because an SMU can source voltage or current while measuring voltage and current, it has similar hardware qualities to a curve tracer, he added.

The new software leverages the touchscreen interface of 2400 Series graphical SMUs to recreate the familiar user experience of a curve tracer for low-power two-terminal devices. The Keithley I-V Tracer uses the full capabilities of supported SMUs, including the dual high-speed digitizers of the Keithley 2461, to perform tracing with AC polarity and pulsed DC, in addition to standard DC polarity.

This maps to the classic Tektronix 576, for example, that had +DC, –DC, and AC polarities, which means the output is either + voltage, – voltage, or both + and – voltages, said Gorley.

Fig. 1: Keithley I-V Tracer software leverages the touchscreen interface of 2400 Series graphical SMUs to recreate the familiar user experience of a curve tracer for low-power two-terminal devices.

Over the years, curve tracers became more sophisticated, complex, and expensive and are now used primarily for comprehensive semiconductor device-level characterization.

“These advances left an unfilled void for the simple interaction model of classic curve tracers, which continue to be in demand for failure analysis and education applications,” said Gorley. “This has led to a robust market for used traditional curve tracers, with refurbished Tektronix 370Bs fetching $20,000 or more in online auctions.

“Unfortunately, classic instruments are largely impractical due to their cost, limited availability, lack of support, and large footprint. In contrast, Keithley SMUs are a fraction of the size of a classic curve tracer, come with full factory support, and provide the full capabilities of a graphical SMU.”

Fig. 2: An SMU with Keithley I-V Tracer software is a fraction of the size of a classic curve tracer.

Gorley said that curve tracers are popular because they provide precise control and immediate results. If too much power is sourced through a device, it’s possible to destroy the sensitive evidence that points to the root cause of failure. The Keithley I-V Tracer simulates this functionality by providing direct control over the output level, letting failure analysis (FA) engineers slowly ramp up to an I-V curve anomaly, then seamlessly creep into the behavior, with a minimum of 500-nV (or 500-fA) resolution on the sourced output.

Besides failure analysis, curve tracers are popular in engineering classrooms thanks to their simplicity. Similarly, Keithley I-V Tracer software gives students real-time, direct control, allowing them to experiment themselves and solidify understanding on a wide range of electronics, Gorley said.

The Keithly I-V Tracer is priced at $1,499 plus the cost of the SMU. See the software in action here.