LOW LEVEL MEASURE & SOURCE
A Greater Measure of Confidence
www.keithley.com
1.888.KEITHLEY (U.S. only)
Precision low current sourcing
6220 and 6221
•Source and sink (programmable
load) 100fA to 100mA
•1014W output impedance
ensures stable current sourcing
into variable loads
•65000-point source memory
allows executing comprehensive
test current sweeps directly
from the current source
•Built-in RS-232, GPIB, Trigger
Link, and digital I/O interfaces
•Reconfigurable triax output
simplifies matching the
application’s guarding
requirements
•Model 220 emulation mode
eliminates need to reprogram
existing applications
6221 Only
•Source AC currents from 4pA
to 210mA peak to peak for AC
charac ter iza tion of components
and materials. The 6221’s
10MHz output update rate
generates smooth sine waves
up to 100kHz
•Built-in standard and arbitrary
waveform generators with
1mHz to 100kHz frequency
range. Applications include use
as a complex programmable
load or sensor signal and for
noise emulation
•Programmable pulse widths
as short as 5µs, limiting power
dissipation in delicate com-
ponents. Supports pulsed I-V
measurements down to 50µs
when used with Model 2182A
Nanovoltmeter
•Built-in Ethernet interface for
easy remote control without a
GPIB controller card
The Model 6220 DC Current Source and Model 6221 AC and DC Current Source combine ease of use
with exceptionally low current noise. Low current sourcing is critical to applications in test environ-
ments ranging from R&D to production, especially in the semiconductor, nanotechnology, and super-
conductor industries. High sourcing accuracy and built-in control functions make the Models 6220
and 6221 ideal for applications like Hall measurements, resistance measurements using delta mode,
pulsed measurements, and differential conductance measurements.
The need for precision, low current sourcing. Device testing and characterization for today’s very
small and power-efficient electronics requires sourcing low current levels, which demands the use of
a precision, low current source. Lower stimulus currents produce lower—and harder to measure—
voltages across the device. Combining the Model 6220 or 6221 with a Model 2182A Nanovoltmeter
makes it possible to address both of these challenges.
AC current source and current source waveform generator. The Model 6221 is the only low
current AC source on the market. Before its introduction, researchers and engineers were forced to
build their own AC current sources. This cost-effective source provides better accuracy, consistency,
reliability, and robustness than “home-made” solutions. The Model 6221 is also the only commercially
available current source waveform generator, which greatly simplifies creating and outputting com-
plex waveforms.
Simple programming. Both current sources are fully programmable via the front panel controls or
from an external controller via RS-232 or GPIB interfaces; the Model 6221 also features an Ethernet
interface for remote control from anywhere there’s an Ethernet connection. Both instruments can
source DC currents from 100fA to 105mA; the Model 6221 can also source AC currents from 4pA to
210mA peak to peak. The output voltage compliance of either source can be set from 0.1V to 105V in
10mV steps. Voltage compliance (which limits
the amount of voltage applied when sourcing
a current) is critical for applications in which
overvoltages could damage the device under
test (DUT).
Drop-in replacement for the Model 220
current source. These instruments build upon
Keithley’s popular Model 220 Programmable
Current Source; a Model 220 emulation mode
makes it easy to replace a Model 220 with a
Model 6220/6221 in an existing application with-
out rewriting the control code.
Define and execute current ramps easily.
Both the Models 6220 and 6221 offer tools for
defining current ramps and stepping through
predefined sequences of up to 65,536 output
values using a trigger or a timer. Both sources
support linear, logarithmic, and custom sweeps.
APPLICATIONS
•Nanotechnology
– Differential conductance
– Pulsed sourcing and resistance
•Optoelectronics
– Pulsed I-V
•Replacement for AC resistance
bridges (when used with Model
2182A)
– Measuring resistance with
low power
•Replacement for lock-in
amplifiers (when used with
Model 2182A)
– Measuring resistance with
low noise
6220
6221
DC Current Source
AC and DC Current Source
LOW LEVEL MEASURE & SOURCE
www.keithley.com
1.888.KEITHLEY (U.S. only)
A Greater Measure of Confidence
The Model 6221’s combination of high source resolution and megahertz update rates makes it capable
of emulating high fidelity current signals that are indistinguishable from analog current ramps.
Free Instrument Control Example Start-up Software
The instrument control example software available for the sources simplifies both performing basic
sourcing tasks and coordinating complex measurement functions with the Keithley Model 2182A. The
software, developed in the LabVIEW® programming environment, includes a step-by-step measure-
ment guide that helps users set up their instruments and make proper connections, as well as pro-
gram basic sourcing functions. The advanced tools in the package support delta mode, differential
conductance, and pulse mode measurements. From this package, users can print out the instrument
commands for any of the pre-programmed functions, which provides a starting point for incorporat-
ing these functions into customized applications.
Differential Conductance
Differential conductance measurements are among the most important and critical measurements
made on non-linear tunneling devices and on low temperature devices. Mathematically, differential
conductance is the derivative of a device’s I-V curve. The Model 6220 or 6221, combined with the
Model 2182A Nano voltmeter, is the industry’s most complete solution for differential conductance
measurements. Together, these instruments are also the fastest solution available, providing 10× the
speed and significantly lower noise than other options. Data can be obtained in a single measure-
ment pass, rather than by averaging the result of multiple sweeps, which is both time-consuming and
prone to error. The Model 622X and Model 2182A are also easy to use because the combination can
be treated as a single instrument. Their simple connections eliminate the isolation and noise current
problems that plague other solutions.
Figure 1. Perform, analyze, and display differential conductance measurements.
Delta Mode
Keithley originally developed the delta mode method for making low noise measurements of voltages
and resistances for use with the Model 2182 Nanovoltmeter and a triggerable external current source.
Essentially, the delta mode automatically triggers the current source to alternate the signal polarity,
then triggers a nanovoltmeter reading at each polarity. This current reversal technique cancels out
any constant thermoelectric offsets, ensuring the results reflect the true value of the voltage.
This same basic technique has been incorporated into the Model 622X and Model 2182A delta
mode, but its implementation has been dramatically enhanced and simplified. The technique can
now cancel thermoelectric offsets that drift over time, produce results in half the time of the previ-
ous technique, and allow the source to control and configure the nanovoltmeter, so setting up the
measurement takes just two key presses. The improved cancellation and higher reading rate reduces
measurement noise to as little as 1nV.
Ordering Information
6220 DC Precision Current Source
6221 AC and DC Current Source
6220/2182A
Complete Delta Mode
System, w/DC Current
Source, Nanovoltmeter,
and all necessary cables
(GPIB cables not included)
6221/2182A
Complete Delta Mode
System, w/AC and DC
Current Source, Nano volt-
meter, and all necessary
cables (GPIB cables
not included)
Accessories Supplied
237-ALG-2 6.6 ft (2m), Low Noise,
Input Cable with Triax-
to-Alligator Clips
8501-2 6.6 ft (2m) Trigger Link
Cable to connect 622x
to 2182A
CA-180-3A Ethernet Crossover
Cable (6221 only)
CA-351 Communication Cable
between 2182A and 622x
CS-1195-2 Safety Interlock
Connector
Instruction manual on CD
Getting Started manual (hardcopy)
Software (downloadable)
ACCESSORIES AVAILABLE
7006-* GPIB Cable with Straight-On Connector
7007-1 Shielded IEEE-488 Cable, 1m (3.3 ft)
7007-2 Shielded IEEE-488 Cable, 2m (6.6 ft)
7078-TRX-5 5 ft (1.5m), Low Noise, Triax-to-Triax Cable
(Male on Both Ends)
KPCI-488LPA IEEE-488 Interface/Controller for the PCI Bus
KUSB-488B IEEE-488 USB-to-GPIB Interface Adapter
SERVICES AVAILABLE
6220-3Y-EW 1-year factory warranty extended to 3 years from
date of shipment
6221-3Y-EW 1-year factory warranty extended to 3 years from
date of shipment
C/6220-3Y-ISO 3 (ISO-17025 accredited) calibrations within 3
years of purchase*
C/6221-3Y-ISO 3 (ISO-17025 accredited) calibrations within 3
years of purchase*
*Not available in all countries
6220
6221
DC Current Source
AC and DC Current Source
Precision low current sourcing
LOW LEVEL MEASURE & SOURCE
A Greater Measure of Confidence
www.keithley.com
1.888.KEITHLEY (U.S. only)
Precision low current sourcing
The delta mode enables measuring low voltages and resistances accurately. Once the Model 622X and
the Model 2182A are connected properly, the user simply presses the current source’s Delta button,
followed by the Trigger button, which starts the test. The Model 622X and the Model 2182A work
together seamlessly and can be controlled via the GPIB interface (GPIB or Ethernet with the Model
6221). The free example control software available for the Model 622X includes a tutorial that “walks”
users through the delta mode setup process.
Pulsed Tests
Even small amounts of heat introduced by the measurement process itself can raise the DUT’s tem-
perature, skewing test results or even destroying the device. The Model 6221’s pulse measurement
capability minimizes the amount of power dissipated into a DUT by offering maximum flexibility
when making pulsed measurements, allowing users to program the optimal pulse current amplitude,
pulse interval, pulse width, and other pulse parameters.
The Model 6221 makes short pulses (and reductions in heat dissipation) possible with microsecond
rise times on all ranges. The Model 6221/2182A combination synchronizes the pulse and measure-
ment—a measurement can begin as soon as 16µs after the Model 6221 applies the pulse. The entire
pulse, including a complete nanovolt measurement, can be as short as 50µs. Line synchronization
between the Model 6221 and Model 2182A eliminates power line related noise.
Standard and Arbitrary Waveform Generator
The Model 6221 is the only low current AC source on the market. It can be programmed to gen-
erate both basic waveforms (sine, square, triangle, and ramp) and customizable waveforms with
an arbitrary waveform generator (ARB) that supports defining waveforms point by point. It can
generate waveforms at frequencies ranging from 1mHz to 100kHz at an output update rate of
10 megasamples/ second.
Performance Superior to AC Resistance Bridges and Lock-In Amplifiers
The Model 622X/2182A combination provides many advantages over AC resistance bridges and lock-in
amplifiers, including lower noise, lower current sourcing, lower voltage measurements, less power
dissipation into DUTs, and lower cost. It also eliminates the need for a current pre-amplifier.
Models 6220 and 6221 vs.
Homemade Current Sources
Many researchers and engineers who need a
current source attempt to get by with a volt-
age source and series resistor instead. This is
often the case when an AC current is needed.
This is because, until the introduction of the
Model 6220/6221, no AC current sources were
available on the market. However, homemade
current sources have several disadvantages vs.
true current sources:
•Homemade Current Sources Don’t Have
Voltage Compliance. You may want to be
sure the voltage at the terminals of your
homemade “current source” never exceeds
a certain limit (for example, 1–2V in the
case of many optoelectronic devices). The
most straightforward way to accomplish
this is to reduce the voltage source to that
level. This requires the series resistor to
be reduced to attain the desired current. If
you want to program a different current,
you must change the resistor while the
voltage is held constant! Another possibility
is to place a protection circuit in parallel
with the DUT. These do not have precise
voltage control and always act as a parallel
device, stealing some of the programmed
current intended for the DUT.
•Homemade Current Sources Can’t Have
Predictable Output. With a homemade
“current source” made of a voltage source
and series resistor, the impedance of the
DUT forms a voltage divider. If the DUT
resistance is entirely predictable, the
current can be known, but if the DUT
resistance is unknown or changes, as most
devices do, then the current isn’t a simple
function of the voltage applied. The best
way to make the source predictable is to
use a very high value series resistor (and
accordingly high voltage source), which
is in direct contradiction with the need
for compliance.
• While it’s possible to know (if not control)
the actual current coming from such an
unpredictable source, this also comes at a
cost. This can be done with a supplemental
measurement of the current, such as using
a voltmeter to measure the voltage drop
across the series resistor. This measurement
can be used as feedback to alter the voltage
source or simply recorded. Either way,
it requires additional equipment, which
adds complexity or error. To make matters
worse, if the homemade current source
is made to be moderately predictable by
using a large series resistor, this readback
would require using an electrometer to
ensure accuracy.
DC
Measurement
Delta Mode
Measurement
4µV
5nV
Figure 2. Delta mode offers 1000-to-1 noise reduction.
6220
6221 DC Current Source
AC and DC Current Source
LOW LEVEL MEASURE & SOURCE
www.keithley.com
1.888.KEITHLEY (U.S. only)
A Greater Measure of Confidence
Figure 4. The Model 6221 and the free
example start-up control software make it
easy to create complex waveforms by adding,
multiplying, stringing together, or applying
filters to standard wave shapes.
The Model 6221 can also expand the capabilities
of lock-in amplifiers in applications that already
employ them. For example, its clean signals and
its output synchronization signal make it an
ideal output source for lock-in applications such
as measuring second and third harmonic device
response.
Model 2182A Nanovoltmeter
The Model 2182A expands upon the capabilities
of Keithley’s original Model 2182 Nano volt-
meter. Although the Model 6220 and 6221 are
compatible with the Model 2182, delta mode and
differential conductance measurements require
approximately twice as long to complete with
the Model 2182 as with the Model 2182A. Unlike
the Model 2182A, the Model 2182 does not sup-
port pulse mode measurements.
Source Current
1/60 second (1/50 when operating off 50Hz power)
Programmable: 50µs to 12ms
Measurement integration period
Measuring difference voltage eliminates
line frequency noise, DC offsets
Voltage measurement noise at line frequency
Measured response voltage
Pulsed measurement without line sync Line synchronized pulse measurements
Figure 3. Measurements are line synchronized to minimize 50/60Hz interference.
• APPLICATIONS OF
622X/2182A COMBINATION:
•Easy instrument coordination and
intuitive example software simplifies
setup and operation in many
applications.
•Measure resistances from 10nW to
100MW. One measurement system
for wide ranging devices.
•Low noise alternative to AC
resistance bridges and lock-in
amplifiers for measuring resistances.
•Coordinates pulsing and
measurement with pulse widths as
short as 50µs (6221 only).
•Measures differential conduc-
tance up to 10× faster and with
lower noise than earlier solutions
allow. Differential conductance is
an important parameter in semi-
con ductor research for describing
density of states in bulk material.
•Delta mode reduces noise in low
resistance measurements by a factor
of 1000.
•For low impedance Hall measure-
ments, the delta mode operation of
the Model 622X/2182A combination
provides industry-leading noise
performance and rejection of contact
potentials. For higher impedance
Hall measurements (greater than
100MW), the Model 4200-SCS can
replace the current source, switching,
and multiple high impedance
voltage measurement channels. This
provides a complete solution with
pre-programmed test projects.
6220
6221 DC Current Source
AC and DC Current Source
Precision low current sourcing
LOW LEVEL MEASURE & SOURCE
A Greater Measure of Confidence
www.keithley.com
1.888.KEITHLEY (U.S. only)
Model 6220 and 6221 specifications
Source Specifications
Range
(+5% over
range)
Accuracy
(1 Year)
23°C ±5°C
±(% rdg. + amps)
Programming
Resolution
Temperature
Coefficient/°C
0°–18°C &
28°–50°C
Typical Noise
(peak-peak)/RMS 3
0.1Hz–10Hz
6221 Only
Settling Time 1, 2
(1% of Final Value)
Typical Noise
(peak-peak)/RMS 3
10Hz–(Bw)
Output
Response
Bandwidth
(BW) Into
Short
Output
Response
Fast (Typical3)
(6221 Only)
6220, 6221
with Output
Response
Slow (Max.)
2 nA 0.4 % + 2 pA 100 fA 0.02 % + 200 fA 400 / 80 fA 250 / 50 pA 10 k Hz 90 µs 100 µs
20 nA 0.3 % + 10 pA 1 pA 0.02 % + 200 fA 4 / 0.8 pA 250 / 50 pA 10 kHz 90 µs 100 µs
200 nA 0.3 % + 100 pA 10 pA 0.02 % + 2 pA 20 / 4 pA 2.5 / 0.5 nA 100 k Hz 30 µs 100 µs
2 µA 0.1 % + 1 nA 100 pA 0.01 % + 20 pA 200 / 40 pA 25 / 5.0 nA 1 MHz 4 µs 100 µs
20 µA 0.05% + 10 nA 1 nA 0.005% + 200 pA 2 / 0.4 nA 50 0 / 10 0 n A 1 MHz 2 µs 100 µs
200 µA 0.05% + 100 nA 10 nA 0.005% + 2 nA 20 / 4 nA 1.0 / 0.2 µA 1 MHz 2 µs 100 µs
2 mA 0.05% + 1 µA 100 nA 0.005% + 20 nA 200 / 40 nA 5.0 / 1 µA 1 MHz 2 µs 100 µs
20 mA 0.05% + 10 µA 1 µA 0.005% + 200 nA 2 / 0.4 µA 20 / 4.0 µA 1 MHz 2 µs 100 µs
100 mA 0.1 % + 50 µA 10 µA 0.01 % + 2 µA 10 / 2 µA 100 / 20 µA 1 MHz 3 µs 100 µs
ADDITIONAL SOURCE SPECIFICATIONS
OUTPUT RESISTANCE: >1014W (2nA/20nA range).
OUTPUT CAPACITANCE: <10pF, <100pF Filter ON
(2nA/20nA range).
LOAD IMPEDANCE: Stable into 10µH typical, 100µH for 6220,
or for 6221 with Output Response SLOW.
VOLTAGE LIMIT (Compliance): Bipolar voltage limit set with
single value. 0.1V to 105V in 0.01V programmable steps.
MAX. OUTPUT POWER: 11W, four quadrant source or
sink operation.
GUARD OUTPUT ACCURACY: ±1mV for output currents <2mA
(excluding output lead voltage drop).
PROGRAM MEMORY: Number of Locations: 64K. Offers
point-by-point control and triggering, e.g. sweeps.
MAX. TRIGGER RATE: 1000/s.
RMS NOISE 10Hz–20MHz (2nA–20mA Range): Less than
1mVrms, 5mVp-p (into 50W load).
SOURCE NOTES
1. Settling times are specified into a resistive load, with a maximum
resistance equal to 2V/ Ifull scale of range. See manual for other
load conditions.
2. Settling times to 0.1% of final value are typically <2× of 1%
settling times.
3. Typical values are non warranted, apply at 23°C, represent the 50th
percentile, and are provided solely as useful information.
2182A MEASUREMENT FUNCTIONS
DUT RESISTANCE: Up to 1GW (1ns) (100MW limit for
pulse mode).
DELTA MODE RESISTANCE MEASUREMENTS AND
DIFFERENTIAL CONDUCTANCE: Controls Keithley Model
2182A Nanovoltmeter at up to 24Hz reversal rate (2182 at up
to 12Hz).
PULSE MEASUREMENTS (6221 ONLY):
Pulse Widths: 50µs to 12ms, 1pA to 100mA.
Repetition Interval: 83.3ms to 5s.
ARBITRARY FUNCTION GENERATOR
(6221 only)
WAVEFORMS: Sine, Square, Ramp, and 4 user defined arbitrary
waveforms.
FREQUENCY RANGE: 1mHz to 100kHz.5
FREQUENCY ACCURACY4: ±100ppm (1 year).
SAMPLE RATE: 10 MSPS.
AMPLITUDE: 4pA to 210mA peak-peak into loads up to 1012W.
AMPLITUDE RESOLUTION: 16 bits (including sign).
AMPLITUDE ACCURACY (<10kHz): 5
Magnitude: ±(1% rdg + 0.2% range).
Offset: ±(0.2% rdg + 0.2% range).
SINE WAVE CHARACTERISTICS:
Amplitude Flatness: Less than 1dB up to 100kHz.6
SQUARE WAVE CHARACTERISTICS:
Overshoot: 2.5% max.6
Variable Duty Cycle: 4 Settable to 1µs min. pulse duration,
0.01% programming resolution.
Jitter (RMS): 100ns + 0.1% of period.6
RAMP WAVE CHARACTERISTICS:
Linearity: <0.1% of peak output up to 10kHz.6
ARBITRARY WAVE CHARACTERISTICS:
Waveform Length: 2 to 64K points.
Jitter (RMS): 100ns + 0.1% of period.6
WAVEFORM NOTES
4. Minimum realizable duty cycle is limited by current range
response and load impedance.
5. Amplitude accuracy is applicable into a maximum resistive
load of 2V/Ifull scale of range. Amplitude attenuation will occur
at higher frequencies dependent upon current range and load
impedance.
6. These specifications are only valid for the 20mA range and a
50W load.
GENERAL
COMMON MODE VOLTAGE: 250V rms, DC to 60Hz.
COMMON MODE ISOLATION: >109W, <2nF.
SOURCE OUTPUT MODES: Fixed DC level, Memory List.
REMOTE INTERFACE:
IEEE-488 and RS-232C.
SCPI (Standard Commands for Programmable
Instruments).
DDC (command language compatible with Keithley
Model 220).
PASSWORD PROTECTION: 11 characters.
DIGITAL INTERFACE:
Handler Interface: Start of test, end of test, 3 category
bits, +5V@300mA supply.
Digital I/O: 1 trigger input, 4 TTL/Relay Drive outputs
(33V@500mA, diode clamped).
OUTPUT CONNECTIONS:
Teflon insulated 3-lug triax connector for output.
Banana safety jack for GUARD, OUTPUT LO.
Screw terminal for CHASSIS.
DB-9 connector for EXTERNAL TRIGGER INPUT,
OUTPUT, and DIGITAL I/O.
Two position screw terminal for INTERLOCK.
INTERLOCK: Maximum 10W external circuit impedance.
POWER SUPPLY: 100V to 240V rms, 50–60Hz.
POWER CONSUMPTION: 120VA.
ENVIRONMENT:
For Indoor Use Only: Maximum 2000m above sea level.
Operating: 0°–50°C, 70%R.H. up to 35°C. Derate
3% R.H./°C, 35°–50°C.
Storage: –25°C to 65°C, guaranteed by design.
EMC: Conforms to European Union Directive 89/336/EEC,
EN 61326-1.
SAFETY: Conforms to European Union Directive
73/23/EEC, EN61010-1.
VIBRATION: MIL-PRF-28800F Class 3, Random.
WARMUP: 1 hour to rated accuracies.
Passive Cooling: No fan.
DIMENSIONS:
Rack Mounting: 89mm high × 213mm wide × 370mm
deep (3.5 in. × 8.375 in. × 14.563 in.).
Bench Configuration (with handle and feet): 104mm
high × 238mm wide × 370mm deep (4.125 in. × 9.375
in. × 14.563 in.).
6220
6221 DC Current Source
AC and DC Current Source
