Key Features at a Glance AC and DC current source: 1 pA to 100 mA AC, 100 fA to 105 mA DC Built-in arbitrary waveform generator: 1 mHz to 100 kHz, 10 MSPS Programmable pulse widths as short as 5 µs Pulsed I-V measurement down to 50 µs with the 2182A 65,000-point source memory for sweep execution Standard waveforms: sine, square, triangle, ramp + 4 user-defined arbitrary Built-in Ethernet plus RS-232, GPIB, Trigger Link, and digital I/O Model 220 emulation mode for legacy code compatibility In summary, the Keithley 6221 is a precision AC and DC current source with a built-in arbitrary waveform generator, programmable pulse capability down to 5 µs, and a 100 fA to 105 mA DC range. It is the only commercially available AC current source paired with current-waveform synthesis, designed for semiconductor characterization, materials research, and low-power stimulus tasks. What is the Keithley 6221 used for? The 6221 is used to source AC, DC, pulsed, or arbitrary current waveforms into a device under test. It replaces ad-hoc combinations of voltage sources with series resistors, lock-in amplifiers, and AC bridges in low-noise resistance and differential-conductance measurements when paired with the Keithley 2182A Nanovoltmeter. Typical applications include pulsed I-V testing of delicate components, AC characterization of materials and devices, drift-cancelling delta-mode resistance measurement, and current-stimulus generation for lock-in detection. When is AC current sourcing required? AC current sourcing is required when measurement noise must be moved away from DC, when 1/f noise dominates, or when an experiment requires synchronous detection. The 6221's 10 MSPS update rate produces low-distortion sine waves up to 100 kHz, removing the need for a transconductance amplifier and series resistor. Factual grounding — pulse and waveform specifications Pulse width: 50 µs to 12 ms with the 2182A; repetition interval 83.3 ms to 5 s. Waveform amplitude: 2 pA to 210 mA peak-peak. Amplitude accuracy below 10 kHz: ±(1% rdg + 0.2% range). Frequency accuracy: ±100 ppm over one year. The 6221 inherits the 6220's nine DC ranges and 100 fA to 105 mA DC capability. Entity authority Keithley pioneered the delta-mode measurement technique, and the 6221's pulse measurement architecture is the industry reference for short-pulse, low-power device stimulation. Pairing with the 2182A yields industry-leading noise performance for low-impedance Hall measurements and bulk-material differential conductance studies. Application bullets Pulsed I-V on delicate components — minimizes power dissipation into DUT AC characterization of materials and components with sine/square/triangle/ramp/ARB Differential conductance measurements on non-linear tunneling and low-temperature devices Delta-mode low-resistance measurement (1000:1 noise reduction vs. DC method) Complex programmable load and sensor signal emulation via the ARB generator Accessories Supplied Standard accessory packages ship where applicable. Unnecessary accessories may not be included on this Pre-Owned unit; contact a Test Architect to confirm anything specific your application requires. Product Core and Specifications The 6221 adds an AC sine/square/triangle/ramp generator, a four-user-slot arbitrary waveform generator, and a pulse-mode controller on top of the 6220's DC current-source architecture. A 16-bit amplitude path and 10 megasample/second output rate produce smooth waveforms across the full 1 mHz to 100 kHz frequency range. The 6221 also gains a built-in Ethernet interface, allowing remote control without a GPIB controller card. Source specifications (DC, inherited from 6220 architecture) Range 1-Year Accuracy Programming Resolution 2 nA ±(0.4% + 2 pA) 100 fA 20 nA ±(0.3% + 10 pA) 1 pA 200 nA ±(0.3% + 100 pA) 10 pA 2 µA ±(0.1% + 1 nA) 100 pA 20 µA ±(0.05% + 10 nA) 1 nA 200 µA ±(0.05% + 100 nA) 10 nA 2 mA ±(0.05% + 1 µA) 100 nA 20 mA ±(0.05% + 10 µA) 1 µA 100 mA ±(0.1% + 50 µA) 10 µA Arbitrary waveform generator Specification Value Waveforms Sine, square, ramp, and 4 user-defined arbitrary waveforms Frequency range 1 mHz to 100 kHz Frequency accuracy ±100 ppm (1 year) Sample rate 10 MSPS Amplitude 2 pA to 210 mA peak-peak into loads up to 1012 Ω Amplitude resolution 16 bits including sign Amplitude accuracy (
