Source AC and DC current

Two new current sources from Keithley provide assistance with low current measurements. When you need an AC current source, you often must build one and drive it with a voltage source. Keithley's Model 6221 simplifies your work by producing both AC current and DC current. The companion source, the Model 6220, produces DC current only but has the same DC specs as the Model 6221.

The Model 6221 produces AC currents from 1 pA to 100 mA. The standard and arbitrary waveform generators sample the signals at speeds up to 10 MHz, thus producing smooth sine waves at frequencies to 100 kHz. Both models have an output impedance of 10¹⁴ Ω, so most loads won't affect it.

For DC current, both models can source or sink current from 100 fA to 100 mA. They can act as programmable loads to sink current (the units are programmable through IEEE 488 and RS-232 ports, and the Model 6221 comes with an Ethernet port). Both units can emulate Keithley's older Model 220, making them drop-in replacements.

Prices: Model 6221—$3995; Model 6220—$2995. Keithley Instruments, Cleveland, OH. www.keithley.com.