Fluorescence Spectroscopy


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The CFD-2G is a hybrid amplifier-discriminator module designed for use with a wide variety of single photon detectors.  It is neatly packaged to allow positioning close to the detector in order to minimise signal degradation, and features USB interface for simplified configuration.


Each module features:

  • Amplifier with bandwidth up to 2GHz
  • Constant fraction discriminator (CFD)
  • Simultaneous NIM and TTL-compatible outputs
  • Detector overload protection (operates in conjunction with HV supply)
  • USB and F-link PC interfaces (control panel software included)
  • Programmable non-volatile settings for gain, threshold, walk, and trip count rate (USB cable may be removed once module is configured)
  • Visual LED indication of activity
  • 15V power requirement

The CFD-2G's unique combination of features makes it particularly well suited to applications involving low gain detectors where immunity to interference and signal degradation is a critical consideration.  Its compact dimensions permit it to be close-coupled to MCP and NIR detection modules keeping the connection between the detector and the amplifier very short.  Furthermore, since the amplifier and discriminator are on the same board, direct conversion to digital (NIM and TTL) means there is no requirement to expose the analogue amplifier output to an external connector.

A detector overload feature allows the programming of a count rate monitor threshold that can be used to deactivate the detector's high voltage supply in order to protect the detector from damage due to over-illumination.  This feature operates in conjunction with the HORIBA Scientific Fluoro3PS HV power supply.

The CFD-2G is available in 4 variants optimised for different types of detector:



PMT type


Transit Time Spread (TTS)


MCP-PMT (e.g. R3809 series)




Fast risetime PMT (e.g. H10330 series)




Side-window type  PMT (e.g. R928)




Head-on type PMT (e.g. R5509)

Typically >3ns


Applications include: 

  • Time-resolved fluorescence detection
  • Chemi-luminescence detection
  • Bioluminescence
  • Time-of-flight mass spectrometry
  • Single molecule detection
  • Photon correlation spectroscopy

Manufactured by HORIBA



20dB to 30dB programmable (40dB option available)

Threshold adjustment

-10mV to -200mV

Input connector

SMA type

Output connectors

Lemo00 (NIM, Camac)

NIM output

-0.8V peak at 5ns duration (50-Ohm termination)

TTL output

>2V peak at 5ns duration (50-Ohm termination)

Re-trigger rate



Host, Limit, Count, Power

Power requirement

15V DC


13.5cm x 20cm x 3.9cm


0.47 kg

Specifications and appearance are subject to change without notice

CFD-2G example data

CFD-2G-A Example data - 34ps (FWHM) prompt with R3809 MCP-PMT and DeltaDiode laser.