Keithley Instruments 428 Data Sheet

428-PROG Programmable Current Amplifier

The Model 428-PROG Programmable Current Amplifier converts fast, small currents to a voltage, which can be easily digitized or displayed by an oscilloscope, waveform analyzer, or data acquisition system. It uses a sophisticated “feedback current” circuit to achieve both fast rise times and sub-picoamp noise. The gain of the

• 2µs rise time

• 1.2fA rms noise

• Up to 10

• IEEE-488 interface

V/A gain

Ordering Information

428-PROG

Extended warranty, service, and calibration contracts are available.

Programmable Current Amplifier with IEEE-488 Interface

Model 428-PROG is adjustable in decade increments from 10 rise times from 2µs to 300ms.

The Model 428-PROG offers fast response at low current levels, which is unmatched by either electrometers or picoammeters. The nine cur rent amplification ranges allow the greatest flexibility in making speed/noise tradeoffs. The Model 428-PROG can be used with any of Keithley’s data acquisition boards to implement a very cost-effective, low curreent measurement system with wide bandwidth and fast response.

The Model 428-PROG incorporates a second-order Bessel-function filter that minimizes noise without increasing rise time on high-gain ranges. This can be defeated in situations where 6dB/octave roll-off is desired, as in control loops of scanning tunneling electron microscopes.

Input and output connections to the Model 428PROG are made with BNC connectors. INPUT HI is connected to a programmable ±5V supply, which permits suitable bias voltages to be applied to devices-under-test or current collectors. This eliminates the need for a separate bias supply.

For applications where voltage offset errors exist, the ZERO CHECK and OFFSET functions can be used, thereby maintaining maximum instrument accuracy. Current suppression is also available up to 5mA, useful for suppressing background currents, such as dark currents.

The Model 428-PROG also incorporates an exte rior design with simple front panel operation, improved display, and convenient system integration. Pushbutton controls have an LED to indicate if that function is activated. The display features three selectable intensities (bright, dim, and off) for use in light-sensitive environments. All setup values can be displayed from the front panel. An IEEE-488 interface is included.

The Model 428-PROG as Preamplifier to an Oscilloscope

The Model 428-PROG can be connected to an oscilloscope or waveform digitizer to display very low currents in real time.

APPLICATIONS

The Model 428-PROG satisfies a broad range of applications in research and device labs due to its cost-effective ability to amplify fast, low currents. A few of these applications include:

Biochemistry Measurements:

• Ion channel currents through cell walls and membranes

Beam Position Monitoring:

• Used on electron storage rings and

synchrotrons

face Science Studies:

Sur

Scanning T

• system amplifier

• Observation of secondary electron emission, as in X

Laser and Light Measurements:

• Fast, sensitive amplifier for use with PMTs and photodiodes

• Analysis of fast photoconductive materials.

• IR detector amplifier

Transient Phenomena:

Current DL

• Breakdown in devices and dielectric

• materials

V/A to 1011V/A, with selectable

unneling Electron Microscope

-ray and beam line currents

TS studies

Converts small, fast currents to a voltage

1.888.KEITHLEY (U.S. only)

www.keithley.com

A GR

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LOW LEVEL MEASUR E & SOURCE

428-PROG

Programmable Current Amplifier

CCURACY

AIN SETTING 18°–28°C COEFFICIENT (10%–90%) NOISE (10%–90%) NOISE DC INPUT

V/A ±(% input + offset) ±(% input + offset)/°C ms rms µs

0.45 + 1.2 µA 0.01 + 40 nA 0.1 90 nA 2 100 nA < 0.6Ω

0.31 + 120 nA 0.01 + 4 nA 0.1 9 nA 2 15 nA < 0.7Ω

.31 + 12 nA 0.01 + 400 pA 0.1 900 pA 5 2 nA < 1.6

.34 + 1.2 nA 0.01 + 40 pA 0.1 90 pA 10 500 pA < 10

.5 + 122 pA 0.015 + 4.3 pA 0.1 9 pA 15 200 pA < 100

.4 + 14 pA 0.015 + 700 fA 1 0.5 pA 40 30 pA < 1k

2.5 + 3 pA 0.025 + 300 fA 10 50 fA 100 10 pA < 10kΩ

2.5 + 1.6 pA 0.025 + 250 fA 100 4 fA 250 2 pA < 100kΩ

EMPERATURE RISE TIME

OW NOISE

ISE TIME

AXIMUM SPEED

rms

1011* 2.7 + 1.6 pA 0.028 + 250 fA 300 1.2 fA 250 2 pA < 100kΩ

When properly zeroed using zero correct.

electable filtering will improve noise specifications; see operator’s manual for details (typical value shown).

andwidth = 0.35/rise time.

ith up to 100pF shunt capacitance; autofilter on; low pass filter off.

* 10

SPECIFICATIONS

NPUT:

Voltage Burden:

100µA; 20µV/°C temperature coefficient.

Maximum Overload: 100V on 104to 1011V/A ranges; 10V on 103V/A range. Higher

voltage sources must be current limited at 10mA.

OUTPUT:

Model 428-PROG specifications

Range: Impedance: <100Ω DC–175kHz.

LOW PASS FILTER:

Ranges: Attenuation: 12dB/octave.

GAIN ×10: Rise time, noise, and input resistance are unchanged when selecting GAIN

×10; gain accuracy and temperature coefficient are degraded by 0.2% and

0.003%/°C respectively.

CURRENT SUPPRESSION

setting is 10

setting with GAIN ×10 enabled; other entries are for GAIN ×10 disabled.

<200µV (18°–28°C) for inputs <100µA; <10mV for inputs ≥

±10V, 1mA; bias voltage off.

10µs to 300ms (±25%) in 1, 3, 10 sequence or OFF.

ACCURACY

GENERAL

DISPLAY: Ten character alphanumeric LED display with normal/dim/off intensity control. REAR PANEL CONNECTORS:

Input BNC: Output BNC: Common connected to chassis. IEEE-488 Connector 5-Way Binding Post:

EMI/RFI: Complies with the RF interference limits of FCC Part 15 Class B and VDE 0871 Class B. EMC: Conforms to European Union Directive 89/336/EEC. SAFETY: Conforms to European Union Directive 73/23/EEC (meets EN61010-1/IEC 1010). WARM-UP: 1 hour to rated accuracy. ENVIRONMENT: Operating: 0°–50°C, <70% R.H. up to 35°C; linearly derate R.H. 3%/°C up to 50°C.

Storage: –25°C to 65°C.

POWER: 105–125VAC or 210–250VAC, switch selected. (90–110/180–220VAC available.) 50Hz or 60Hz. 45VA

maximum.

DIMENSIONS: 90mm high × 213mm wide × 397mm deep (31⁄2 in × 83⁄8 in × 155⁄8 in).

Common connected to chassis through 1kΩ.

Connected to chassis.

RANGE RESOLUTION ±(%setting + offset)

±5 nA 1 pA 3.0 + 10 pA

±50 nA 10 pA 1.6 + 100 pA

±500 nA 100 pA 0.8 + 1 nA

±5 µA 1 nA 0.7 + 10 nA

±50 µA 10 nA 0.6 + 100 nA

±500 µA 100 nA 0.6 + 1 µA

±5 mA 1 µA 0.6 + 10 µA

PROGRAMMABLE PARAMETERS: All parameters and controls programmable except for IEEE-488 bus address. EXECUTION SPEED: (measured from DAV true to RFD true on bus).

Zero Correct & Auto Suppression commands: <3s. Save/Recall Configuration commands: <500ms. All other commands: <40ms.

IEEE-488 BUS IMPLEMENTATION

BIAS VOLTAGE:

±5V.

Range: Resolution: 2.5mV Accuracy: ±

(1.1%rdg + 25mV).

CABLES

4801

ACCESSORIES AVAILABLE

Low Noise BNC Input Cable, 1.2m (4 ft)

ADAPTERS

7078-TRX-BNC 3-Slot Male Triax to Female BNC Adapter KUSB-488 USB-to-GPIB Interface Adapter for USB Port (requires 7010 Adapter)

RACK MOUNTS

4288-1 4288-2

Single Fixed R Dual Fixed R

ack Mount Kit

RESISTANCE

Ω Ω Ω

Ω