DC Bias Module for Mounted Photodiodes

Overview
Photodiode
Example Circuits
Feedback

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Female SMA Photodiode Output Connector (Top) and 2.5 mm Phono Jack DC Input (Bottom)

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Female BNC Photodiode Input Connector

Features

Module for Biasing Our Mounted Photodiodes
Maximum Bandwidth: 350 MHz
Post Mountable via Bottom-Located 8-32 and M4 Taps
Compact Size: 2.48" x 1.40" x 0.80" (63.0 mm x 35.6 mm x 20.3 mm)

The PBM42 Bias Module allows a DC bias voltage from a user-supplied, external source to be applied to photodiodes. Designed for use with our mounted photodiodes, the module can accept an input bias voltage from -25 to +25 V from a user-supplied source and has a maximum bandwidth of 350 MHz (dependent on the photodiode). By adding a reverse bias to a photodiode, the width of the depletion junction in the photodiode is increased, thereby increasing the responsivity, decreasing the junction capacitance, and improving the linearity of the response. Operating under these conditions can produce a larger dark current, depending on the photodiode material.

The input side of the bias module has a BNC connector that can be connected to any of our mounted photodiodes equipped with the same connector by using a BNC cable or T3533 BNC adapter. Alternatively, the input side can be connected to any of our mounted photodiodes with SMA connectors by using an SMA-to-BNC cable or T4288 SMA-to-BNC adapter.

The bias module has an SMA connector on the output side and a 2.5 mm phono jack for the DC voltage input. A 36"-long cable with a 2.5 mm phono plug on one end and bare wires on the other is included with the module. Please note that the photodiode should be operated with a reverse bias. Forward biasing the photodiode can cause damage. For cathode-grounded photodiodes, the tip of the phono plug must be positive. For anode-grounded photodiodes, the tip of the phono plug must be negative. We recommend using a low-noise power supply with the module. For grounding and reverse bias voltage information on all our mounted photodiodes, please see the Photodiode tab.

For best frequency performance, the output of the bias module should be terminated with a 50 Ω cable and a 50 Ω impedance device or terminator, such as our T4119. For flexibility in output voltage, the VT2 variable terminator can also be used.

To ensure electrical isolation of the connectors and to protect the photodiode, the compact housing of the PBM42 is constructed from Delrin^®. Additionally, the housing offers one 8-32-tapped hole and one M4-tapped hole for mounting on our Ø1/2" posts, as shown in the photo at the top of the page.

Specifications
Item #	Bias Voltage	Cutoff Frequency^a	Photodiode Input Connector	Output Connector	DC Input Connector	Housing Dimensions	Operating/Storage Temperature
PBM42	-25 to +25 V	350 MHz	Female BNC	Female SMA	2.5 mm Phono (Cable Included)	2.48" x 1.40" x 0.80" (63.0 mm x 35.6 mm x 20.3 mm)	0 to 40 °C

Determined by the Photodiode Used

Thorlabs' Mounted Photodiodes Key Specifications

Item #	Material	Grounding	Reverse Bias Voltage (Max)	Bandwidth^a
SM1PD1A	Silicon	Cathode Grounded	25 V	8.8 MHz
SM1PD1B	Silicon	Anode Grounded	25 V	8.8 MHz
SM1PD2A	UV-Enhanced Silicon	Cathode Grounded	5 V	7.8 MHz
SM1PD5A	Germanium	Cathode Grounded	1 V	0.12 MHz
SM05PD1A	Silicon	Cathode Grounded	25 V	35 MHz
SM05PD2A	Silicon	Cathode Grounded	30 V	350 MHz
SM05PD4A	InGaAs	Cathode Grounded	5 V	50 MHz
SM05PD5A	InGaAs	Cathode Grounded	3 V	5.3 MHz
SM05PD6A	Germanium	Cathode Grounded	3 V	0.70 MHz
SM05PD7A	GaP	Cathode Grounded	5 V	350 MHz
SM05PD1B	Silicon	Anode Grounded	20 V	35 MHz
SM05PD2B	Silicon	Anode Grounded	30 V	350 MHz

Bandwidth is calculated from the rise time of the photodiode, which is specified at the peak responsivity wavelength and may vary at other wavelengths. Note that the PBM42 module can support photodiode bandwidths up to 350 MHz; hence, it is an appropriate module for use with any of Thorlabs' mounted photodiodes.

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Example Circuit Diagram for Attaching the PBM42 Bias Module to a Cathode-Grounded Photodiode

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Example Circuit Diagram for Attaching the PBM42 Bias Module to an Anode-Grounded Photodiode

Posted Comments:

henry.ke (posted 2018-09-11 02:22:10.69)

我使用SM1PD5A detector +PBM42,逆向偏壓3V,但發現電流增加到3mA就飽和了,若沒有使用PBM42時,detector電流可以非常線性的到10mA沒有問題請教一下使用逆向偏壓的目的不就是要增加線性度嗎?

YLohia (posted 2018-10-05 01:54:29.0)

Hello, thank you for contacting Thorlabs. Inside the PBM42 is an RC circuit used for cleaning up the noise from the power supply but also to current limit and protect the PD in the case it is reverse connected. The resistor is limiting the current in your case that causes saturation. Please note that the bandwidth is also affected since the voltage drop across the resistor lowers the bias voltage, which results in a larger junction capacitance and lowers the bandwidth.

juyoungk (posted 2015-02-18 15:55:03.613)

Hi, I am confused of what the proper polarity is for the reverse bias of my photodiode. In manual page 6, it says, "For Cathode grounded diodes center pin of phone plug is positive. For Anode grounded diodes center pin of phone plug is negative." I purchased Cathode grounded diode (SM1PD1A). Should I apply positive voltage on the center pin of phone plug? I would appreciate your help. Thank you.

jlow (posted 2015-02-24 04:45:07.0)

Response from Jeremy at Thorlabs: The SM1PD1A is cathode grounded so you should apply a positive voltage to the tip of the phono plug.

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DC Bias Module for Mounted Photodiodes

Features

Thorlabs' Mounted Photodiodes Key Specifications