# How to amplify voltage to meet the needs of a photodiode/APD

• Robert Dietrich
In summary, the individual needs to find a way to run two photodiodes for two hours off of a lightweight battery with a bias voltage of at least 40V. They are considering using op amps, but are concerned about the battery draining too quickly. The photodiodes being used have a peak reverse voltage of 40V and can possibly work at a lower voltage, according to the data sheet. A web search revealed potential circuit examples using op amps for this purpose.

## Homework Statement

I need to be able to run two photodiodes that require a bias voltage of at least 40V (this might need to be a little bigger, as I'm planning on using them for scintillation detection). They need to be able to run for two hours off of a lightweight battery. This is because they will be on a weather balloon for a long ride (this is my senior seminar project) and the weight of the payload can't be too high.

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## The Attempt at a Solution

I was thinking of using a series of op amps, but I'm concerned that simply using op amps to increase the output voltage of (for example) a 9V battery will drain the battery too quickly. A link to the specific photodiodes I'm using is http://www.mouser.com/ProductDetail/First-Sensor/PS10-5B-TO52S13/?qs=sGAEpiMZZMt9rZLnhhqRzxxh2B7IPT45 [Broken]

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The data sheet for that photodiode (at the site you reference) shows that 40V is the peak reverse voltage for that part. Are you sure you want to exceed that?

A brief web search on photodiode circuit examples turned up something that might be of interest here. Check out items 9 and 10.

For an opamp to produce a 40 V output its power source must already be equal to or greater than 40 V unless you're doing something with current pumps (voltage doublers or triplers).

Your photodiode is specified to work at 3.5V reverse voltage with a bit better bandwidth at 20V. Most probably works fine at 3.5V.

## 1. How does a photodiode/APD work?

A photodiode or avalanche photodiode (APD) is a semiconductor device that converts light into electrical current. When light strikes the diode, it creates electron-hole pairs, which can then be collected as current. APDs use an internal avalanche multiplication process to amplify this current.

## 2. What is the purpose of amplifying voltage for a photodiode/APD?

The purpose of amplifying voltage for a photodiode/APD is to increase the sensitivity of the device. By amplifying the current produced by the diode, the signal can be stronger and easier to detect, allowing for more accurate measurements of light intensity.

## 3. How do you choose the appropriate voltage amplification for a photodiode/APD?

The appropriate voltage amplification for a photodiode/APD depends on the desired sensitivity and the specifications of the diode. It is important to consider the maximum voltage and current ratings of the diode, as well as the noise level and dynamic range of the signal. A higher amplification may increase sensitivity, but it can also introduce more noise into the signal.

## 4. What types of circuits are commonly used to amplify voltage for a photodiode/APD?

There are several types of circuits that can be used to amplify voltage for a photodiode/APD, including transimpedance amplifiers, operational amplifiers, and voltage amplifiers. The choice of circuit will depend on the specific application and requirements for the device.

## 5. Are there any considerations when designing a voltage amplification circuit for a photodiode/APD?

Yes, there are several considerations when designing a voltage amplification circuit for a photodiode/APD. These include the frequency response of the circuit, the input and output impedance, and the stability of the circuit. It is also important to carefully choose the components and ensure proper grounding to minimize noise in the signal.