Keithley releases precision dc, ac/dc current sources

Keithley Instruments Inc. has introduced its Model 6221 ac/dc current source and Model 6220 dc current source.


Keithley Instruments claims its Model 6221 ac/dc current source is the only commercially available current source waveform generator.

Keithley Instruments Inc . has introduced its Model 6221 ac/dc current source and Model 6220 dc current source.

Model 6221 reportedly is the only ac current source on the market. Until now, Keithley reports that researchers and engineers have been forced to build their own ac current sources.

Model 6221 provides better accuracy, consistency, reliability, robustness, and cost effectiveness than homemade solutions. It's also the only commercially available current source waveform generator, which simplifies creating and outputting complex waveforms. Pulse widths as short as 5 microseconds can be programmed, and the instrument supports pulsed I-V measurements.

Models 6220 and 6221 combine ease of use with exceptionally low current noise. Low current sourcing is critical to applications in test environments, ranging from R&D to production, especially in the semiconductor, nanotechnology, and superconductor sectors. High-sourcing accuracy and built-in control functions make models 6220 and 6221 ideal for applications such as Hall measurements, resistance measurements using delta mode, pulsed measurements, and differential conductance measurements, which is an increasingly common measurement for characterizing semiconductor and nanotechnology materials.

Both current sources are fully programmable via the front panel controls or from an external controller via RS-232 or GPIB interfaces. Model 6221 also features an Ethernet interface for remote control from anywhere there's an Ethernet connection. Both instruments can source dc currents from 100 fA to 100 mA. Model 6221 can also source ac currents from 1 pA to 100 mA.

Also, models 6220 and 6221 offer tools for defining current ramps and stepping through pre-defined sequences of up to 64,000 output values using a trigger or a timer. Both sources support linear, logarithmic, and custom sweeps. Model 6221's combination of high source resolution and megahertz update rates makes it capable of producing high fidelity current signals that are indistinguishable from analog current ramps.

In addition, device testing and characterization for today's very small and power-efficient electronics requires sourcing low current levels with great precision. Lower stimulus currents produce lower, and harder to measure, voltages across the device. Combining the Model 6220 or Model 6221 with a Keithley Model 2182A Nanovoltmeter makes it possible to address both challenges.

Finally, when used with the Keithley Model 2182A Nanovoltmeter, both the Model 6220 and Model 6221 measure resistances from 10 nohm to 1 Gohm. Used in this way, Model 6221 acts as a high performance alternative to ac resistance bridges and lock-in amplifiers for measuring resistances and coordinates pulsing and measurement with pulse widths as short as 50 microseconds. The combination measures differential conductance up to 10 times faster and with lower noise than earlier solutions allow, and can be used in delta mode, which improves resistance measurements up to 1,000 times. Included control software simplifies setup and operation.

—James Montague, news editor, Control Engineering,

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