THORLABS PDA30B User Manual

PDA30B
Ge Switchable Gain Detector

User Guide

InGaAs Biased Detector

Page 1 August 2, 2012

Table of Contents

Chapter 1 Warning Symbol Definitions ............................................. 2

Chapter 2 Description ......................................................................... 3

Chapter 3 Setup ................................................................................... 3

Chapter 4 Operation ............................................................................ 4

4.1. Theory of Operation ................................................... 4

4.2. Responsivity ............................................................... 4

4.3. Dark Current ............................................................... 5

4.4. Bandwidth and Response ............................................ 5

4.5. Terminating Resistance .............................................. 5

4.6. Gain Adjustment ......................................................... 6

Chapter 5 Troubleshooting ................................................................. 7

Chapter 6 Specifications ..................................................................... 8

6.1. Response Curve ........................................................ 10

6.2. Mechanical Drawing ................................................. 11

Chapter 7 Certificate of Conformance ............................................. 12

Chapter 8 Regulatory ........................................................................ 13

Chapter 9 Thorlabs Worldwide Contacts ........................................ 14

Chapter 1: Warning Symbol Definitions

23155-D02, Rev A Page 2

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, Spinning Blades May Cause Harm

InGaAs Biased Detector

Page 3 August 2, 2012

Chapter 2 Description

The PDA30B is an amplified, switchable-gain, silicon detector designed for
detection of light signals over 800 – 1800nm wavelength range. An eight-position
rotary switch allows the user to vary the gain in 10 dB steps. A buffered output
drives 50 load impedances up to 5 volt. The PDA30B housing includes a
removable threaded coupler (SM1T1) and retainer ring (SM1RR) that is
compatible with any number of Thorlabs 1” threaded accessories. This allows
convenient mounting of external optics, light filters, apertures, as well as
providing an easy mounting mechanism using the Thorlabs cage assembly
accessories.

Chapter 3 Setup

The detector can be set up in many different ways using our extensive line of
adapters. However, the detector should always be mounted and secured for best
operation.

1. Unpack the optical head, install a Thorlabs TR-series ½” diameter post
into one of the #8-32 (M4 on -EC version) tapped holes, located on the
bottom and side of the head, and mount into a PH-series post holder.

2. Connect the power supply 3-pin plug into the power receptacle on the
PDA30B.

3. Plug the power supply into a 50-60Hz, 100-120VAC outlet (220-240VAC
for -EC version).

4. Attach a 50 coax cable (i.e. RG-58U) to the output of the PDA. When
running cable lengths longer than 12” we recommend terminating the
opposite end of the coax with a 50 resistor (Thorlabs p/n T4119) for
maximum performance. Connect the remaining end to a measurement
device such as an oscilloscope or high speed DAQ card. Caution: Many
high speed oscilloscopes have input impedances of 50. In this case,
do not install a 50 terminator. The combined loads will equal 25
which could allow ~135mA of output current. This will damage the
output driver of the PDA30B.

5. Power the PDA30B on using the power switch located on the top side of
the unit.

6. Install any desired filters, optics, adapters, or fiber adapters to the input
aperture. Caution: The PDA30B was designed to allow maximum
accessibility to the photodetector by having the front surface of the
diode flush with the outside of the PDA housing. When using fiber
adapters, make sure that the fiber ferrule does not crash into the
detector. Failure to do so may cause damage to the diode and / or the
fiber. An easy way to accomplish this is to install a SM1RR retaining

Chapter 4: Operation

23155-D02, Rev A Page 4

ring (included with the PDA30B) inside the 1” threaded coupler before
installing the fiber adapter.

7. Apply a light source to the detector. Adjust the gain to the desired
setting.

Caution!

The PDA30B was designed to allow maximum accessibility to the

photodetector by having the front surface of the diode flush with the

outside of the PDA housing. When using fiber adapters, make sure that the

fiber ferrule does not crash into the detector. Failure to do so may cause

damage to the diode and or the fiber. An easy way to accomplish this is to

install a SM1RR retaining ring (included with the PDA30B) inside the 1"

threaded coupler before installing the fiber adapter

Chapter 4 Operation

4.1. Theory of Operation

Thorlabs PDA series are ideal for measuring both pulsed and CW light sources.
The PDA30B includes a reverse-biased PIN photo diode, mated to a switchable
gain transimpedance amplifier, and packaged in a rugged housing.

4.2. Responsivity

The responsivity of a photodiode can be defined as a ratio of generated
photocurrent (I

PD

) to the incident light power (P) at a given wavelength:

󰇛󰇜=







Photodetector

Transimpedance Amp

Out

Feedback

R

F

A

B

-V

BNC

GND

GND GND

R

LOAD

!

!

InGaAs Biased Detector

Page 5 August 2, 2012

4.3. Dark Current

Dark current is leakage current which flows when a bias voltage is applied to a
photodiode. The PDA with Transimpedance Amplifier does control the dark
current flowing out. Looking at the figure 1 above, it can be noted that Point B is
held at a “Virtual Ground” and will try to hold point A to the same value. This
minimizes the amount of dark current present in the system.

The dark current present is also affected by the photodiode material and the size
of the active area. Silicon devices generally produce low dark current compared
to germanium devices which have high dark currents. The table below lists
several photodiode materials and their relative dark currents, speeds, sensitivity,
and costs.

Material

Dark

Current Speed

Sensitivity1

(nm) Cost

Silicon (Si) Low High 400 – 1000 Low
Germanium (Ge) High Low 900 – 1600 Low
Gallium Phosphide (GaP) Low High 150 – 550 Med

Indium Gallium Arsenide
(InGaAs)

Low High 800 – 1800 Med

Extended Range: Indium
Gallium Arsenide (InGaAs)

High High 1200 – 2600 High

4.4. Bandwidth and Response

A load resistor will react with the photodetector junction capacitance to limit the
bandwidth. For best frequency response, a 50  terminator should be used in
conjunction with a 50  coaxial cable. The gain of the detector is dependent on
the feedback element (R

F

). The bandwidth of the detector can be calculated

using the following:

󰇛−3󰇜=





4



×



Where GBP is the amplifier gain bandwidth product and C

D

is the sum of the

photodiode junction capacitance and the amplifier capacitance.

4.5. Terminating Resistance

A load resistance is used to convert the generated photocurrent into a voltage
(V

OUT

) for viewing on an oscilloscope:

Depending on the type of the photodiode, load resistance can affect the
response speed. For maximum bandwidth, we recommend using a 50  coaxial

1.Approximate values, actual wavelength values will vary from unit to unit

Chapter 4: Operation

23155-D02, Rev A Page 6

cable with a 50  terminating resistor at the opposite end of the cable. This will
minimize ringing by matching the cable with its characteristic impedance. If
bandwidth is not important, you may increase the amount of voltage for a given
light level by increasing R

LOAD

. In an unmatched termination the length of the
coaxial cable can have a profound impact on the response, so it is recommended
to keep the cable as short as possible.

The maximum output of the PDA30B is 2 volts for high impedance loads (i.e.
R

Load

> 5 k) and 1 volts for 50  loads. Adjust the gain so that the measured
signal level out of the PDA30B is below 2 volts (1 volts with a 50  load) to avoid
saturation.

For low terminating resistors, <5 k or 1% error, an additional factor needs to be
included in the above formula. As described above the output includes a 50
series resistor (RS). The output load creates a voltage divider with the 50 series
resistor as follows:

=









+







=

ℜ

󰇛󰇜

∗∗

4.6. Gain Adjustment

The PDA30B includes a low noise, low offset, high gain transimpedance amplifier
that allows gain adjustment over a 70dB range. The gain is adjusted by rotating
the gain control knob, located on the top side of the unit. There are 8 gain
positions incremented in 10dB steps. It is important to note that the bandwidth
will decrease as the gain increases. See the specifications table in Chapter 6 to
choose the best gain vs. bandwidth for a given input signal.

InGaAs Biased Detector

Page 7 August 2, 2012

Chapter 5 Troubleshooting

Problem Suggested Solutions

There is no signal response. Verify that the power is switched on and all

connections are secure.
Verify the proper terminating resistor is installed if

using a Voltage measurement device.
Verify that the optical signal wavelength is within the

specified wavelength range.
Verify that the optical signal is illuminating the

detector active area.

Output Voltage will not increase.
Detector Output is skewed.

Check to make sure the detector is not saturated.
Refer to the Output Voltage spec. in the
Specifications table.

Install a 1” Lens Tube(SM1L10) to the thread
coulpler (SM1T1) to baffle any external light sources
to see if this improves the response.

Chapter 6: Specifications

23155-D02, Rev A Page 8

Chapter 6 Specifications

Performance Specifications

0 dB Setting

40 dB Setting

Gain2 (Hi-Z) 1.51 x 103 V/A ±2% Gain1 (Hi-Z) 1.51 x 105 V/A ±2%

Gain1 (50 Ω) 0.75 x 103 V/A ±2% Gain1 (50 Ω) 0.75 x 105 V/A ±2%

Bandwidth 460 kHz Bandwidth

6.50 kHz

Noise (RMS) 223 µV Noise (RMS)

220 V

NEP (@ λp) 4.44 x 10

-11

W/√Hz NEP (@ λp)

3.10 x 10

-12

W/√Hz

Offset 15mV (20mV max) Offset 15mV (20mV max)

10 dB Setting

50 dB Setting

Gain1 (Hi-Z) 4.75 x 103 V/A ±2% Gain1 (Hi-Z) 4.75 x 105 V/A ±2%

Gain1 (50 Ω) 2.38 x 103 V/A ±2% Gain1 (50 Ω) 2.38 x 105 V/A ±2%

Bandwidth

230 kHz

Bandwidth

2 kHz

Noise (RMS)

240 V

Noise (RMS)

220 V

NEP (@ λp)

2.08 x 10

-11

W/√Hz

NEP (@ λ

p

)

1.95 x 10

-12

W/√Hz

Offset

15mV (20mV max)

Offset

15mV (20mV max)

20 dB Setting

60 dB Setting

Gain1 (Hi-Z) 1.5 x 104 V/A ±2% Gain1 (Hi-Z) 1.5 x 106 V/A ±5%

Gain1 (5 0Ω) 0.75 x 104 V/A ±2% Gain1 (50 Ω) 0.75 x 106 V/A ±5%

Bandwidth 80 kHz Bandwidth 630 Hz

Noise (RMS)

223 V

Noise (RMS)

250 V

NEP (@ λp)

9.87 x 10

-12

W/√Hz

NEP (@ λ

p

)

4.79 x 10

-12

W/√Hz

Offset

15mV (20mV max)

Offset:

15mV (20mV max)

30 dB Setting

70 dB Setting

Gain1 (Hi-Z) 4.75 x 104 V/A ±2% Gain1 (Hi-Z) 4.75 x 106 V/A ±5%

Gain1 (50 Ω) 2.38 x 104 V/A ±2% Gain1 (50 Ω) 2.38 x 106 V/A ±5%

Bandwidth 20 kHz Bandwidth 200Hz

Noise (RMS) 220 V Noise (RMS) 500 µV
NEP (@ λp)

4.36 x 10

-12

W/√Hz

NEP (@ λ

p

)

3.38 x 10

-12

W/√Hz

Offset

15mV (20mV max)

Offset

15mV (20mV max)

2

All measurements performed with a 50 Ω load unless stated otherwise.

3

The PDA30B has a 50 Ω series terminator resistor (i.e. in series with amplifier output). This forms a

voltage divider with any load impedance (e.g. 50 Ω load divides signal in half).

InGaAs Biased Detector

Page 9 August 2, 2012

Electrical Specifications

Detector Ge
Active Area Ø3.0mm (7.0mm2)
Wavelength Range  800 to 1800 nm
Peak Wavelength  p 1550 nm (Typ)

Peak Response

ℜ( 

p

)

0.88 A/W (Typ)

Output Impedance 50 
Max Ouput Current I

OUT

100 mA

Load Impedance 50  to Hi-Z
Gain Adjustment Range 0 dB to 70 dB
Gain Steps 8 x 10dB Steps
Output Voltage V

OUT

0 to 5 V (50 )

0 to 10 V (Hi-Z)

General

On/Off Switch Slide
Gain Switch 8 Position Rotary
Output BNC (DC Coupled)
Package Size 2.76" x 2.06" x 0.88"

(70.1 mm x 52.3 mm x 22.4 mm)

PD Surface Depth 0.16" (4.1 mm)
Weight 0.15 kg
Accessories SM1T1 Coupler

SM1RR Retainer Ring

Storage Temp -20 to 125 °C
Operating Temp 0 to 70 °C
AC Power Supply AC – DC Converter
Input Power 31W

100-200 VAC (50 to 60Hz)

220-240 VAC (50 to 60 Hz)

3

1. Although the power supply is rated for 31W the PDA30B actual usage is <5W over the full

operating range.

Chapter 6: Specifications

23155-D02, Rev A Page 10

6.1. Response Curve

0.0

0.2

0.4

0.6

0.8

1.0

800 1000 1200 1400 1600 1800

Responsivity (a/w)

Wavelength (nm)

DET30B Spectral Response

InGaAs Biased Detector

Page 11 August 2, 2012

6.2. Mechanical Drawing

Please visit the web for a more detailed mechanical drawing.

A

2.06"

(52.3 mm)

1.08"

(27.4 mm)

0.88"

(22.4 mm)

Detail A

Scale 2:1

1.035"-40 External Threading
Mates with SM1 Line

Indicator Power

LED

Output BNC

0.08"
(1.9 mm)

Power Supply Connector

0.70"

(17.8 mm)

2.76"

(70.1 mm)

#8-32 x 0.25" Thread

1.70"

(43.2 mm)

0.79"

(20.1 mm)

1.87"

(47.5 mm)

Ø9.8 mm Aperture

0.535"-040 Internal Thread
Mates with SM05 Line

Chapter 7: Certificate of Conformance

23155-D02, Rev A Page 12

Chapter 7 Certificate of Conformance

InGaAs Biased Detector

Page 13 August 2, 2012

Chapter 8 Regulatory

As required by the WEEE (Waste Electrical and Electronic Equipment Directive)
of the European Community and the corresponding national laws, Thorlabs offers
all end users in the EC the possibility to return “end of life” units without incurring
disposal charges.

• This offer is valid for Thorlabs electrical and electronic equipment:

• Sold after August 13, 2005

• Marked correspondingly with the crossed out

“wheelie bin” logo (see right)

• Sold to a company or institute within the EC

• Currently owned by a company or institute

within the EC

• Still complete, not disassembled and not

contaminated

As the WEEE directive applies to self contained
operational electrical and electronic products, this end of
life take back service does not refer to other Thorlabs products, such as:

• Pure OEM products, that means assemblies to be built into a unit by the

user (e.g. OEM laser driver cards)

• Components

• Mechanics and optics

• Left over parts of units disassembled by the user (PCB’s, housings etc.).

If you wish to return a Thorlabs unit for waste recovery, please contact Thorlabs
or your nearest dealer for further information.

8.1. Waste Treatment is Your Own Responsibility

If you do not return an “end of life” unit to Thorlabs, you must hand it to a
company specialized in waste recovery. Do not dispose of the unit in a litter bin
or at a public waste disposal site.

8.2. Ecological Background

It is well known that WEEE pollutes the environment by releasing toxic products
during decomposition. The aim of the European RoHS directive is to reduce the
content of toxic substances in electronic products in the future.

The intent of the WEEE directive is to enforce the recycling of WEEE. A
controlled recycling of end of life products will thereby avoid negative impacts on
the environment.

Wheelie Bin Logo

Chapter 9: Thorlabs Worldwide Contacts

23155-D02, Rev A Page 14

Chapter 9 Thorlabs Worldwide Contacts

USA, Canada, and South America

Thorlabs, Inc.
56 Sparta Avenue
Newton, NJ 07860
USA
Tel: [phone]
Fax: [phone]
www.thorlabs.com
www.thorlabs.us (West Coast)
Email: [e-mail]
Support: [e-mail]

Europe

Thorlabs GmbH
Hans-Böckler-Str. 6
85221 Dachau
Germany
Tel: [phone]
Fax: [phone]
www.thorlabs.de
Email: [e-mail]

UK and Ireland

Thorlabs Ltd.
1 Saint Thomas Place, Ely
Cambridgeshire CB7 4EX
Great Britain
Tel: [phone]
Fax: [phone]
www.thorlabs.com

Email: [e-mail]
Support: [e-mail]

France

Thorlabs SAS
109, rue des Côtes
78600 Maisons-Laffitte
France
Tel: [phone]
Fax: [phone]
www.thorlabs.com
Email: [e-mail]

Scandinavia

Thorlabs Sweden AB
Mölndalsvägen 3
412 63 Göteborg
Sweden
Tel: [phone]
Fax: [phone]
www.thorlabs.com
Email: [e-mail]

Japan

Thorlabs Japan, Inc.
Higashi-Ikebukuro Q Building 1F
2-23-2, Higashi-Ikebukuro,
Toshima-ku, Tokyo 170-0013
Japan
Tel: [phone]
Fax: [phone]
www.thorlabs.jp
Email: [e-mail]

China
Thorlabs China
Room A101, No. 100
Lane 2891, South Qilianshan Road
Putuo District
Shanghai
China
Tel: [phone]
Fax: [phone]
www.thorlabs.hk
Email: [e-mail]

www.thorlabs.com