What is the working principle of phototransistor?

The principle of operation of a phototransistor is similar to a photodiode in combination with an amplifying transistor. The light incident on the base of a phototransistor will induce a small current. This current is then amplified by normal transistor action, which results in a significantly large.

What is the characteristic of a phototransistor?

Definition: A Phototransistor is a device that has the ability to detect the level of the incident radiation and accordingly change the flow of electric current between emitter and collector terminal. It is a 3-layer semiconductor device that consists of a light sensitive base region.

What is phototransistor physics?

3 Phototransistors. A phototransistor is a bipolar or unipolar transistor where light can reach the base, creating optically generated carriers.

What is dark current in phototransistor?

When the phototransistor is placed in the dark and a voltage is applied from collector to emitter, a certain amount of current will flow. This current is called the dark current (ID). This current consists of the leakage current of the collector-base junction multiplied by the dc current gain of the transistor.

What is photodiode and its application?

A photodiode is a semiconductor p-n junction device that converts light into an electrical current. The current is generated when photons are absorbed in the photodiode. Photodiodes may contain optical filters, built-in lenses, and may have large or small surface areas.

What are the applications of phototransistor?

The Areas of application for the Phototransistor include:

• Punch-card readers.
• Security systems.
• Encoders – measure speed and direction.
• IR detectors photo.
• electric controls.
• Computer logic circuitry.
• Relays.
• Lighting control (highways etc)

What are the advantages of phototransistor?

Advantages of Phototransistor Phototransistors produce a higher current than photodiodes. Phototransistors are relatively inexpensive, simple, and small enough to fit several of them onto a single integrated computer chip. Phototransistors are very fast and are capable of providing nearly instantaneous output.

Is phototransistor a photodiode?

A photodiode consists of a semiconductor diode, that generates current when exposed to light. On the other side, phototransistor consists of a junction transistor that when exposed to light energy generates current. A phototransistor is more efficient as compared to a photodiode.

What is the principle of photodiode?

A photodiode is a semiconductor p-n junction device that converts light into an electrical current. The current is generated when photons are absorbed in the photodiode….Photodiode.

What is the working principle of a phototransistor?

Phototransistor Working Principle. A phototransistor is similar to a regular BJT except that the base current is produced and controlled by light instead of a voltage source.

How is a phototransistor similar to a BJT?

Phototransistor Working Principle. A phototransistor is similar to a regular BJT except that the base current is produced and controlled by light instead of a voltage source. The phototransistor effectively converts light energy to an electrical signal.

What happens when there is no light falling on a phototransistor?

When there is no light falling on the phototransistor, a small amount of leakage current known as Dark Current flows from collector to emitter. When there is enough light falling on the base terminal, a base current is produced, which is proportional to the intensity of the light.

What is the dark cur-rent of a phototransistor?

When there is no incident light, there is only a small thermally generated collector-to-emitter leakage current, I CEO; this dark cur- rent is typically in the nA range. When light strikes the collector-base pn junction, a base current, Iλ, is produced that is directly proportional to the light intensity.