Chapter 4 Operation; Output; Gain Adjustment - THORLABS PDA10PT User Manual

Amplified InAsSb Detector
Operation
Chapter 4
This device is a photovoltaic detector and requires a chopped or pulsed input source with a wavelength range
from 1.0 to 5.8 µm. The AC-coupled amplifier circuit is designed to minimize noise.
Power Toggle Switch
4.1.

Output

The maximum output of the PDA10PT is 10 V for high impedance loads (i.e. R
loads. Adjust the gain so that the measured signal level out of the PDA10PT is below 10 V (5 V for a 50 Ω load) to
avoid saturation. If necessary, use external neutral density filters to reduce the input light level. The BNC output
signal is buffered with an amplifier capable of driving 50 Ω loads. A 50 Ω series resistor is included on the output
to impedance match a 50 Ω coax cable. For best performance, we recommend operating the PDA10PT with a 50
Ω terminating load located at the end of the coax cable. While this is not necessary, it eliminates ringing and
distortion due to impedance mismatches.
4.2.

Gain Adjustment

The PDA10PT includes a low-noise, low-offset, high-gain amplifier that allows gain adjustment over a 40 dB
range. The gain is adjusted by rotating the gain control knob located on the side of the unit. There are 8 gain
positions incremented in 6 dB steps. To adjust the gain, follow the steps below.
1) Set the Gain Switch to 0 dB.
2) Turn on the light source.
3) Adjust the gain setting so the output of the detector is below the saturation level as indicated by section 4.1 above.
Rev F, March 11, 2019
Figure 2 Gain Control, LPF Control, and Power Selector
Chapter 4: Operation
Bandwidth Filter
Selector Switch
Gain Selector
Switch
> 5 kΩ) and 5 V for 50 Ω
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