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 Accessory Description 237-ALG-2 6.6 ft (2 m) Low Noise Input Cable with Triax-to-Alligator Clips 8501-2 6.6 ft (2 m) Trigger Link Cable to connect 622x to 2182A CA-180-3A Ethernet Crossover Cable (6221 only) CA-351A Communication Cable between 2182A and 622x CS-1195-2 Safety Interlock Connector Documentation Instruction manual on CD; Getting Started manual (hardcopy); software (downloadable) 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 (
