FEATURES The Model 428 Current Amplifier provides current-to-voltage conversion on eight ranges between 10³V/A and 10¹⁰V/A (10¹¹V/A with X1O gain enabled). Very fast response time allows the unit to be used in difficult applications such as in measuring very small, transient currents. Key Model 428 features include: • Enhanced current suppression: multiple current suppression ranges between ±5nA and ±5mA allow a wide range of steady-state currents to be suppressed. An automatic suppression feature simplifies the current suppression process. • Programmable bias voltage: allows a fixed DC bias voltage from ±2.5mV to ±5V to be applied to the device connected to the input of the Model 428. • Fast response time: 2µsec rise time (10-90%) at 10³ and 10⁴ V/A gain (and 10⁵V/A with xlO gain enabled) for fast current to voltage conversion. • Programmable rise time filter The rise time of the filter can be programmed for values between 10µsec and 300msec. • Zero check: opens the input thus zeroing the output for easy checking of instrument offsets. Zero correct will automatically zero the input amplifier's voltage offset, to typically <50µV of offset • Ease of use: simplified front panel design and versatile firmware for easy front panel setup and use. • IEEE-488 interface (Model428-PROG only): allows the unit to be programmed and controlled from a computer for automated instrument operation. • Adjustable display intensity: normal/dim/off display modes for low-light or photosensitive applications.