Light Dependent Resistor vs. Phototransistor

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SUMMARY

The discussion clarifies the distinctions between a Light Dependent Resistor (LDR) and a phototransistor. An LDR changes resistance based on light intensity, while a phototransistor combines the properties of a photodiode and a standard transistor, allowing for current amplification with a current amplification factor (β) ranging from 50 to 300. Phototransistors exhibit greater sensitivity compared to photodiodes but have slower response times. The conversation suggests that the question may be more appropriate for engineering-focused forums.

PREREQUISITES
  • Understanding of basic electronic components, specifically LDRs and phototransistors.
  • Knowledge of current amplification factors in transistors.
  • Familiarity with photodiode functionality and characteristics.
  • Basic principles of light intensity measurement in electronics.
NEXT STEPS
  • Research the operational principles of phototransistors and their applications in circuits.
  • Explore the characteristics and uses of photodiodes in comparison to phototransistors.
  • Investigate current amplification factors (β) in various transistor types.
  • Learn about the design considerations for circuits utilizing LDRs and phototransistors.
USEFUL FOR

Electronics enthusiasts, engineering students, and professionals involved in circuit design and light-sensing applications will benefit from this discussion.

flash
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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).
 
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.
 

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