Light Dependent Resistor vs. Phototransistor

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On the other hand, a phototransistor is a light sensitive transistor that can amplify the current produced by a photodiode, making it more sensitive. However, it has slower response times compared to photodiodes. It is recommended to post this question in an Engineering forum for more accurate information. In summary, a phototransistor is a light sensitive transistor that combines the properties of a photodiode and a normal transistor, making it more sensitive and having a greater amplification capability. On the other hand, an LDR is a resistor whose resistance changes based on the intensity of light. It is recommended to seek further information in an Engineering forum.
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Hi,
I'm wondering what the difference between a light dependent resistor and a phototransistor is. Am i correct in assuming they are the same if the third lead of the phototransistor is not connected to anything?
Thanks!
 
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From my somewhat limited experience with electronics I seem to recall that phototransistors can amplify the current produced and therefore have a greater sensitivity that of a photodioide, the response times are slower however. This question may be better placed in the Engineering forums (perhaps Berkeman could take a look).
 
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Yes, this question should be in one of the Engineering forums.
A photodiode has an ability to produce large light to dark current ratio. The current produced by a photodiode is of few micro-amperes. A normal transistor has a property to amplify the input current by [itex]\beta[/itex] times where [itex]\beta[/itex] ranges from 50 t0 300 and is known as current amplification factor. A Phototransistor combines the advantages of a photodiode as well as a normal transistor.

LDR as the name suggests is a Light Dependent Resistor whose resistance changes according to the intensity of the light incident on it.
 

FAQ: Light Dependent Resistor vs. Phototransistor

1. What is a Light Dependent Resistor (LDR)?

A Light Dependent Resistor (LDR) is a type of resistor that changes its resistance in response to the amount of light that falls on it. It is also known as a photoresistor or photocell. The resistance of an LDR decreases as the light intensity increases.

2. What is a Phototransistor?

A Phototransistor is a type of transistor that is activated by light. It is a light-sensitive device that is used to detect light and convert it into an electrical signal. When light falls on a phototransistor, it causes a change in the amount of current flowing through it.

3. What is the main difference between an LDR and a phototransistor?

The main difference between an LDR and a phototransistor is that an LDR is a passive component, meaning it does not require an external power source to function. On the other hand, a phototransistor is an active component and requires a power source to operate.

4. In what applications are LDRs and phototransistors commonly used?

LDRs are commonly used in light sensors, camera exposure control, and automatic street light systems. Phototransistors are used in applications such as light meters, burglar alarms, and optocouplers for electrical isolation.

5. Which one is more sensitive, an LDR or a phototransistor?

It depends on the application and the specific components. Generally, phototransistors tend to be more sensitive than LDRs. However, LDRs have a wider range of resistance and can be used in a broader range of light intensities.

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