THORLABS PDA10JT, User Manual

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Amplified MCT Detector Chapter 5: Operation
Page 6 21417-D02
Chapter 5 Operation
This devices is a photoconductive detector and requires a chopped or pulsed input
over a wavelength range from 2.0 to 5.4 µm. The AC-coupled amplifier circuit is
designed to minimize noise.
Figure 2 Gain Control, LPF Control, and Power Selector
5.1. Output
The maximum output of the PDA10JT is 10 V for high impedance loads
(i.e. R
LOAD
> 5 k
Ω) and 5 V for 50 Ω loads. Adjust the gain so that the measured
signal level out of the PDA10JT 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, it is recommended operating the PDA10JT 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.
5.2. Gain Adjustment
The PDA10JT 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 5.1 above.
LPF Selector Switch
Gain Selector
Switch
Power Toggle Switch