THORLABS PDA100A Manual de usuario

PDA100A(-EC)

Si Switchable Gain

Detector

User Guide

Si Amplified Detector with Switch Gain

Table of Contents

Chapter 1Warning Symbol Definitions ...........................................1

Chapter 2Description........................................................................2

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..................................................6

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

Chapter 5Trouble Shooting..............................................................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

Si Amplified Detector with Switch Gain Chapter 1: Warning Symbol Definitions

Rev F, June 30, 2017 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

Si Amplified Detector with Switch Gain Chapter 2: Description

Page 2 13055-D03

Chapter 2 Description

The PDA100A(-EC) is an amplified, switchable-gain, Silicon (Si) detector designed

for detection of light signals ranging from 340 nm to 1100 nm. 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 V. The PDA100A(-EC) 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 Thorlabs’ cage assembly accessories. Also included

is a ±12 V power supply.

ESD Caution

The components inside this instrument are ESD sensitive. Take all appropriate

precautions to discharge personnel and equipment before making any electrical

connections to the unit.

Si Amplified Detector with Switch Gain Chapter 3: Setup

Rev F, June 30, 2017 Page 3

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

PDA100A(-EC).

3. Plug the power supply into a 50 to 60Hz, 100 to 120 VAC outlet (220 to

240 VAC 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 ~135 mA of output current. This will damage the output

driver of the PDA100A(-EC).

5. Power the PDA100A(-EC) on using power switch located on top side of

unit.

CAUTION

The PDA100A(-EC) 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 PDA100A(-EC)] inside the 1" threaded coupler

before installing the fiber adapter.

6. Install any desired filters, optics, adapters, or fiber adapters to the input

aperture.

7. During alignment, take appropriate precautions, such as using reduced

radiation power, or other precautions, and use proper eye and/or skin

protection as recommended by the radiation source manufacturer.

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

Si Amplified Detector with Switch Gain Chapter 4: Operation

Page 4 13055-D03

Chapter 4 Operation

4.1. Theory of Operation

Thorlabs PDA series are ideal for measuring both pulsed and CW light sources.

The PDA100A(-EC) 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 (IPD) to the incident light power (P) at a given wavelength:

󰇛󰇜



Photodetector

Transimpedance Amp

Out

Feedback

-V

BNC

GND

GND GND

LOAD

Si Amplified Detector with Switch Gain Chapter 4: Operation

Rev F, June 30, 2017 Page 5

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 above, it can be noted that Point B is held at

ground and the amplifier will try to hold point A to “Virtual Ground”. This minimizes

the effects 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 (RF). The bandwidth of the detector can be calculated using

the following:

󰇛3󰇜

4

Where GBP is the amplifier gain bandwidth product and CDis the sum of the

photodiode junction capacitance and the amplifier capacitance.

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

Si Amplified Detector with Switch Gain Chapter 4: Operation

Page 6 13055-D03

4.5. Terminating Resistance

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

(VOUT) 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 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 RLOAD. 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 PDA100A(-EC) is 10 volts for high impedance loads

(i.e. RLoad > 5 k) and 5 volts for 50 loads. Adjust the gain so that the measured

signal level out of the PDA100A(-EC) is below 10 volts (5 volts with a 50 load)

to avoid saturation.

For low terminating resistors, <5 kor 1% error, an additional factor needs to be

considered. 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:

 







󰇛󰇜∗∗∗󰇛󰇜

4.6. Gain Adjustment

The PDA100A(-EC) includes a low noise, low offset, high gain transimpedance

amplifier that allows gain adjustment over a 70 dB 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 10 dB steps. It is important to note that the bandwidth will

decrease as the gain increases. See the specifications table on page 8 to choose

the best gain verse bandwidth for a given input signal.

Si Amplified Detector with Switch Gain Chapter 5: Trouble Shooting

Rev F, June 30, 2017 Page 7

Chapter 5 Trouble Shooting

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 table on page 8.

Install a 1" Lens Tube (SM1L10) to the thread

coulpler (SM1T1) to baffle any external light

sources to see if this improves the response.

Si Amplified Detector with Switch Gain Chapter 6: Specifications

Page 8 13055-D03

Chapter 6 Specifications

All performance specifications are typical, performed at 25 °C ambient

temperature, and assume a 50 load, unless stated otherwise.

2The PDA100A(-EC) has a 50 Ωseries terminator resistor (i.e. in series with amplifier

output). This forms a voltage divider with any load impedance (e.g. 50 Ωload divides

signal in half).

3For NIR wavelengths, the rise time of the photodiode element will become slower which

may limit the effective bandwidth of the amplified detector.

Performance Specifications2

0 dB Setting 40 dB Setting

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

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

Bandwidth32.4 MHz Bandwidth4 225 kHz

Noise (RMS) 254 V Noise (RMS) 799 V

NEP (@ p) 2.7. x 10-11 W/Hz NEP (@ p) 3.55 x 10-12 W/Hz

Offset ±5 mV (10 mV max) Offset ±8 mV (15 mV max)

10 dB Setting 50 dB Setting

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

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

Bandwidth41.6 MHz Bandwidth478 kHz

Noise (RMS) 261 V Noise (RMS) 998 V

NEP (@ p) 1.1 x 10-11 W/Hz NEP (@ p) 2.42 x 10-12 W/Hz

Offset ±6 mV (12 mV max) Offset ±8 mV (15 mV max)

20 dB Setting 60 dB Setting

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

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

Bandwidth4860 kHz Bandwidth420 kHz

Noise (RMS) 349 V Noise (RMS) 1163 V

NEP (@ p) 8.91 x 10-12 W/Hz NEP (@ p) 1.22 x 10-12 W/Hz

Offset ±6 mV (15 mV max) Offset ±8 mV (15 mV max)

30 dB Setting 70 dB Setting

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

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

Bandwidth4480 kHz Bandwidth45.9 kHz

Noise (RMS) 561 V Noise (RMS) 1490 µV

NEP (@ p) 4.65 x 10-12 W/Hz NEP (@ p) 9.73 x 10-13 W/Hz

Offset ±8 mV (15 mV max) Offset ±30 mV (Max)

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