Tektronix introduced the industry’s first curve tracer in 1955 to display characteristic curves for vacuum tubes, followed over the years by models for testing transistors, diodes and other solid-state devices. Tektronix curve tracers such as the 576 (below) and 370A/370B went on to broad industry acceptance until production eventually stopped in the mid-eighties. Approximating a power supply and an oscilloscope packaged in the same box, curve tracers source voltage while plotting voltage vs. current.
Over time, curve tracers went on to become more sophisticated, complex and expensive for applications such as comprehensive semiconductor device level characterization. Meanwhile, classic curve tracers never stopped being useful and have continued to remain in demand to this day, primarily for failure analysis and education applications. Their popularity is due in part to a simple interaction model that modern curve tracers have failed to replicate. Since they are no longer being manufactured, the sustained demand has led to a robust market for used traditional curve tracers, with refurbished 370Bs for example fetching $20,000 or more in online auctions.
For labs that prefer to continue using traditional curve tracers, the reliance on vintage instrumentation presents its share of obstacles. Given the cost of usable old instruments, labs typically will share one unit across all their failure analysis engineers. Keeping existing instruments functional requires sourcing and stocking old replacement components, and the rather large footprint consumes limited lab space. And forget about easily capturing and sharing data.
This all changes with the introduction of Keithley I-V Tracer software that brings many of the features loved in classic curve tracers to Keithley SourceMeter® Source Measure Units (SMU). Since an SMU can source voltage or current while measuring voltage and current, it has similar hardware qualities to a curve tracer.
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. I-V Tracer uses the full capabilities of supported SMUs, including the dual high-speed digitizers of the 2461, to perform tracing with AC polarity and pulsed DC, in addition to standard DC polarity. This maps to the 576, for example, that had +DC, -DC, and AC polarities, which means the output is either +voltage, -voltage, or both + and – voltages.
Rather than pooling resources for shared, outdated equipment, labs can now equip individual engineers with their own I-V curve tracer. Keithley SMUs are portable and fit easily on test benches, as shown in the comparison with a 370B below. Moreover, users still have all the source, sink and measure capabilities of Keithley SMUs with curve tracer functionality a click or tap away. It’s also easy to export curves or screenshots, and there’s no need to scour on-line listings for spare parts.
When it comes to failure analysis of semiconductor devices, curve tracers are so popular in part because they provide precise control and immediate results. If you source too much power through a device, it’s possible to destroy the sensitive evidence that points to the root cause of failure. 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.
In addition to failure analysis, curve tracers have long been considered a must-have in engineering classrooms for their simplicity in allowing students to directly apply their learning to electrical devices. I-V Tracer with an SMU offers the same benefit, giving real-time, direct control to students allowing them to experiment themselves and solidify understanding on a wide range of electronics.
Priced at $1,499 plus the cost of the SMU, Keithley I-V Tracer represents a cost-effective way to gain all the usability benefits of a classic curve tracer without the burden that comes with trying to maintain a vintage instrument. For more information, go to: tek.com/keithley-i-v_tracer.