Difference Between Photodiode & Phototransistor

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

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.