Hello, friends, I hope you all are doing great. In today’s tutorial, we will discuss the Difference Between Photodiode & Phototransistor. The basic difference between a photodiode and a phototransistor is that for the transformation light in the current in photodiode, pn junction diode is used while in a phototransistor transistors is used to transform light in the current. The operation of these two devices is based on the inner photoelectric effect.
In a photodiode, a general diode is used that has 2 terminals called anode and cathode. While in a phototransistor normal NPN or PNP transistor is used. The main difference between a transistor and a phototransistor is that in a phototransistor there is no base terminal. This part of the phototransistor is used to get light from the light source. In today’s post, we will have a detailed look at both photodiodes and phototransistors and compare them to find their differences. So let’s get started with the Difference Between a Photodiode & Phototransistor.
Difference Between Photodiode & Phototransistor
Photodiode
- The device that transforms light into electrical energy belongs to the semiconductor family called the photodiode.
- It consists of a PN junction like a normal diode.
- The electric current is produced through this device when light photons collide with the body.
- For light collection, there is an optical filter, and lenses are configured on it.
- Due to the large surface area, they show less value in the response.
- Its example is a solar cell
- Their configuration is like the normal diode with the difference that they can sense light.
- Photonidioe has a PIN junction in place of a PN junction to increase operation response.
- Photondie diode operates in a reverse-biased state.
- When light falls on the PN junction of diode electrons hole pairs are created. This process is called the photoelectric effect.
- The hole goes to the cathode and electrons to the anode and the current produces
- There are two modes of operation: photovoltaic and photoconductive mode
- The output of the photodiode is only current.
- Its output response is faster than the phototransistor.
- It is less sensitive than the phototransistor.
- 2 types of biasing occur in the photodiode forward and reverse bias.
- It used in the solar system for, the detection of UV and infrared rays, for light measurements.
Phototransistor
- The transistor that senses the absorbed light and causes the current flow between the emitter and collector is called a phototransistor.
- There are 3 main parts it has with the base region that is configured to detect light.
- Its structure is like a transistor with the difference it operates on light
- The output mode of the phototransistor is larger than the photodiode
- It generates both current and voltage.
- Its output response is slower than the photodiode.
- It is used in Smoke detectors, compact disc players, invisible light receivers, in laser, etc.
- Its sensitivity level is larger than the photodiode.
- It can only biased in forwarding biased conditions.
Difference between Photodiode and Phototransistor
- The photodiode is a pn junction diode converts the light energy to electrical energy and the phototransistor BJT that transforms the light energy into electrical energy.
- There are two terminals for photodiode and phototransistor has three terminals
- The anode and cathode are terminals of the photodiode and the base, emitter, and collector are terminals of the phototransistor
- Photodiode comes with P and N structure and the transistor has three regions base emitter and collector. The collector is larger and the base is smaller.
- The photodiode has one pn junction and the phototransistor has two pn junction
- PNP and NPN are types of transistors and photodiode has no subtype
- Phototransistors work through forward biased state and photodiodes work in a reverse-biased state
- Photodiodes are only used for light-to-energy conversion and photodiodes are used as switch and amplifier
- The phototransistor is highly sensitive to the photodiode
- The response time of the photodiode is less than the phototransistor
- Prices of the photodiode is less than the transistor
What are the advantages of phototransistor over photodiode?
- The phototransistor is high sensitive than the photodiode with less noise level. High amplification can provided through the use of a photodarlington-type transistor. It is a phototransistor that comes with an emitter output that is configured with a base pin of neibouring.
Is a phototransistor a photodetector?
- The phototransistor is a photodetector that can modulate channel conductance through light absorption causing low dark current high responsivity and good detectivity.
How do phototransistors and photodiodes operate?
- Photodiodes coms with two pins and phototransistors have 3 pins. Phototransistors can used for forward biased mode and photodiode work on reverse biased state. Phototansisor connected with power supply for working ad photodiodes not needed power source.
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That is a detailed post about the difference between phototransistors and photodiodes. If you have any queries ask in comments. I tried my level best to make simple this post for you. Have a good day.