Signal pulses from a PIN photodiode can usually best be read out using a charge sensitive preamplifier (CSP). This is due to the low noise characteristics of CSPs, as well as the integrating nature of the output signal which provides an output proportional to the total charge flowing from the PIN photodiode during the pulse event.
Just a couple examples of pulse-detection applications using PIN photodiodes are the detection of radiation events from scintillators, or the detection of laser pulses.
Connecting a PIN photodiode to the CSP:
The usual connection scheme of a PIN photodiode to the CSP is shown below, and is known as an 'AC coupled' circuit:
Cremat's CR-150-R6 evaluation board uses AC coupling to connect the APD to the CSP module input.
The charge sensitive preamplifier (CSP) shown in the figure above is shown as an 8 pin module. Cremat offers four different CSP modules (CR-110, CR-111, CR-112, and CR-113) which differ primarily by their gain. PIN photodiodes will likely be best served by the CR-110, which has the lowest noise and greatest gain of the available models.
A PIN photodiode based detection setup
An overview of the instrumentation for a PIN photodiode detection setup is shown below. To preserve low noise operation, we highly recommend keeping the cable between the photodiode and the CSP as short as possible.
helpful links:
https://www.cremat.com/cr-150-r6/configuration-1/
https://www.cremat.com/cr-160-r9/
Choice of shaping time in the shaping amplifier
In the diagram above, the shaping amplifier uses a 1 microsecond shaping time, and is a 'middle of the road' choice for many applications. There are, however, some guidelines to help you determine the best shaping time for your application:
1) Choose a shaping time that will give you minimal electronic noise. As was mentioned above, shaping amplifiers are electronic (band pass) filters - the shaping time is related to the band pass frequency. There are a few sources electronic noise in a typical detection system, and some of them differ in their power spectra. While it is outside the scope of this guide to quantify the total electronic noise or provide complicated formulae for calculating the noise minimum, there generally is a noise minimum within the range of available shaping times. Changing the shaping time is a simple matter of swapping out the installed CR-200-X shaping amplifier module for that of another shaping time, so determining the noise minimum could be done experimentally.
2) Choose a shaping time that is long enough to collect all the charge from the pin photodiode. While photodiodes can be fast detectors, the photon signal may have a duration lasting microseconds. For example, detection of a light signal from a CsI(Tl) scintillator occurs over a 2 microsecond duration. In this case and in other applications involving relatively slow signals, use a shaping time that is at least as long as the photon signal duration.
3) Choose a shaping time that is short enough to accommodate the expected counting rate of the detection system.