THORLABS PDAPC4 User manual

PDAPC4
InGaAs Switchable Gain
Photodetector,
OEM Package
User Guide

InGaAs Switchable Gain Detector, OEM
Table of Contents
Chapter 1 Warning Symbol Definitions ...........................................1
Chapter 2 Description........................................................................2
Chapter 3 Setup..................................................................................3
Chapter 4 Operation...........................................................................8
4.1. Theory of Operation......................................................8
4.2. Responsivity .................................................................8
4.3. Dark Current.................................................................8
4.4. Bandwidth and Response ..............................................9
4.5. Terminating Resistance.................................................9
4.6. Gain Adjustment...........................................................9
Chapter 5 Troubleshooting.............................................................10
Chapter 6 Specifications.................................................................11
6.1. Response Curve...........................................................12
6.2. Mechanical Drawing ...................................................13
Chapter 7 Regulatory.......................................................................14
Chapter 8 Thorlabs Worldwide Contacts.......................................15

InGaAs Switchable Gain Detector, OEM Chapter 1: Warning Symbol Definitions
Rev A, May 7, 2021 Page 1
Chapter 1 Warning Symbol Definitions
Below is a list of warning symbols you may encounter in this manual or on your
device.
Symbol
Description
Direct Current
Alternating Current
Both Direct and Alternating Current
Earth Ground Terminal
Protective Conductor Terminal
Frame or chassis Terminal
Equipotentiality
On (Supply)
Off (Supply)
In Position of a Bi-Stable Push Control
Out Position of a Bi-Stable Push Control
Caution, Risk of Electric Shock
Caution, Hot Surface
Caution, Risk of Danger
Warning, Laser Radiation
Caution: ESD Sensitive Components

InGaAs Switchable Gain Detector, OEM Chapter 2: Description
Page 2 TTN239793-D02
Chapter 2 Description
The PDAPC4 is an amplified, switchable-gain, Indium Gallium Arsenide (InGaAs)
photodetector in an OEM package with an operating wavelength range of 800 to
1700 nm. A DIP switch allows the user to vary the gain in 10 dB steps. A buffered
output drives 50 Ωload impedances up to 5 V. The output signal is readable from
the MMCX connector. We provide MMCX to BNC cables (Item # CA3339) or
MMCX to SMA cables (Item # CA3439). Users can also access the digital pins of
the gain switch or the output through an on-board header.
ESD Caution
This product is ESD sensitive. Take all appropriate precautions to
discharge personnel and equipment before making any electrical
connections to the unit.

InGaAs Switchable Gain Detector, OEM Chapter 3: Setup
Rev A, May 7, 2021 Page 3
Chapter 3 Setup
1. The pin out table for the on-board header (J2), Figure 1, is shown in the
two tables below:
Figure 1 J2 Header
J2 PIN OUT
Pin
Designation
Pin
Designation
1
+V
2
GND
3
GND
4
OUTPUT
5
-V
6
N.C.
7
A2
8
A1
9
A0
10
N.C.
Note:
Pins 1 & 5: ±V refers to the power supply positive/negative voltages.
Pins 7, 8, & 9: A0-A2 refers to the three digital pins for the gain adjustment.
Gain Switch Table
A2
A1
A0
Gain
0
0
0
0 dB
0
0
1
10 dB
0
1
0
20 dB
0
1
1
30 dB
1
0
0
40 dB
1
0
1
50 dB
1
1
0
60 dB
1
1
1
70 dB
Pin 10
Pin 1

InGaAs Switchable Gain Detector, OEM Chapter 3: Setup
Page 4 TTN239793-D02
2. Connect a power supply to pins 1, 3, and 5 of the J2 header. The required
power supply voltages are:
J2 Pin
Voltage
1
+12 VDC
3
GND
5
-12 VDC
Thorlabs offers the LD1255-SUPPLY as one compatible power supply
option. Connection to the board is shown below:
Figure 2 Power Supply Connection

InGaAs Switchable Gain Detector, OEM Chapter 3: Setup
Rev A, May 7, 2021 Page 5
3. Digital gain can be adjusted through the J2 header shown in Figure 1 or
using the on-board DIP switch shown below. Each switch is ‘Off’/0 when
in the up position and ‘On’/1 when in the down position.
Figure 3 Location of the On-Board DIP Switches
The following table describes what each switch does:
Switch Number
Function
1
Enable
2
A0
3
A1
4
A2
To enable the DIP switch settings, set switch # 1 to ‘On’/1. See the table
on page 3 for the corresponding gain settings.
Note: The default DIP switch settings are all in the ‘Off’/0 position and
customer could only use J2 Header for gain setting purposes. When the
DIP switch is enabled, it would override the seetings of the J2 Header.
On-Board DIP
Switches

InGaAs Switchable Gain Detector, OEM Chapter 3: Setup
Page 6 TTN239793-D02
4. The side adjusted potentiometer is used to adjust the voltage output’s
offset at high gain settings (e.g. 70 dB). This part is factory pre-adjusted
so normally the user does not need to adjust it. However, if the output
offset value has fallen out of spec, for example drift over time or
temperature, then it is possible to adjust it back by turning this
potentiometer. Turning the screw head clockwise decreases the offset
voltage and adjusting the screw head conterclockwise increases it.
Figure 4 Side adjusted potentiometer
5. Attach a 50 Ωcoax cable to the output of the PDAPC4 detector. Thorlabs
offers two suitable cable options, the CA3339 MMCX to BNC cable or the
CA3439 MMCX to SMA cable.
When running cable lengths longer than 12", Thorlabs recommends
terminating the opposite end of the coax with a 50 Ωresistor for optimal
performance. Thorlabs Item # T4119 is suitable for this purpose.
Potentiometer
Adjustment
Screw Head
MMCX
Connector