Operation; Operating Principle - THORLABS PDA8A2 Abbreviated Operation Manual

PDA8A2

3.3 Operation

Attention
Ensure that the correct mains voltage is selected on the
the power supply to the mains power. Wrong settings for the mains voltage may damage the
power supply. The ±12 V, 250 mA power supply is included, no high voltage power supply is
required for operation.
Electrical Setup
Mount the detector using the combi-thread mounting holes on the side and bottom of
·
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the device.
· Connect the power supply 3-pin plug into the mating receptacle on the PDA8A2.
· Plug the power supply into an outlet.
· Switch on the power supply
· Attach a 50 W coaxial cable (i.e. RG-58U) to the output of the PDA8A2. When running
cable lengths longer than 12", we recommend terminating the opposite end of the coax
with a 50 W resistor (Thorlabs p/n T4119) for maximum performance.
· Connect the remaining end to a measurement device.
· Move the power slider to I. The green LED on the PDA8A2 indicates the correct power
supply.
Optical Setup
· Remove the plastic cover cap that protects the optical input.
Mount external optics if needed.
·
3
· Align the light source with the optical input. The max V
(1.8 V for 50 Ω loads). To avoid electrical saturation, keep the output voltage below the
maximum listed in the
recommended to reduce the input light level in critical cases.
· For maximum linearity performance when measuring focused beams, fiber outputs, or
small diameter beams, do not exceed a maximum intensity of 10 mW/cm
Turning off the PDA8A2
Move the power slider to O after finishing the measurements.

3.4 Operating Principle

In principle, the photodiode generates a current in response to the optical input. The TIA then
converts the current to a voltage and amplifies the signal, reaching a frequency response from
true DC to the cutoff frequency. The fixed gain amplifies the signal to 1.8 V at 50 Ω.
The output is passed through a 50 Ω series resistor before reaching the output connector. The
user can apply either a 50 Ω or high-impedance external load depending on the situation.
The PDA8A2 is powered by an external power supply (±12 V, 200 mA) with switchable 100 V,
120 V or 230 V line voltage. The power supply is connected to the PDA8A2 via a 250 mA,
LUMBERG RSMV3 connector.
4
Technical Data . External neutral density filters or attenuators are
7
power supply prior to connecting
2
is 3.6 V for high impedance loads
out
2
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