Photon counting is the fundamental method for extracting the maximum information from a weak light signal. Coupling an amplifier-descriminator to a photomultiplier achieves this.

An amplifier-discriminator combines a fast amplifier and a fixed-threshold discriminator with an overall sensitivity of approximately one millivolt. With the gain of the photomultiplier optimised, photon counting with a high signal to noise ratio and stability can be achieved up to count rates of 100 MHz.

ET Enterprises offers a range of amplifier-discriminators with output logic levels compatible with commercially available counters. Please refer to the section on the CT2 counter/timer module. A cable, LEADAD6CT2, is available to connect the AD6 to the CT2, and powers the AD6.

The range is summarised in the table below.

Amplifier Descriminator Selection Guide
type input
pulse pair
AD1 50 -1 100 ECL +5V, 25mA 
-5V, 100mA
AD2 50 -0.5 to -2.5 25, 40, 80* ECL +5V, 25mA 
-5V, 100mA
AD3 50 -2 to -5 10 to 100 ECL -5V, 65mA
AD6 50 -2 24 TTL** +5V, 10mA
AD7 50 -2 to -5 24 TTL** +5V, 10mA
AD8 50 -2 25 TTL +5V, 10mA


* preset with external links, please specify when ordering, easily reset
** not suitbale for use with fast counters

Amplifier-discriminators are available as modules in metal cases with BNC input connector and 9-way D-connector output and LV power connection, view an outline drawing here. The AD7, which is pcb mounting, is supplied in a metal case. View an outline drawing here. Examples are also shown in the photograph on this page. They can also be incorporated into housings; please refer to the section on housings.

Read about amplifier-discriminator options here.

© ET Enterprises Limited 2011-2015
ET Enterprises is a trading name of ET Enterprises Limited. Registered in England & Wales, company number 06081468.