Draw the symbol of LED & photodiode. 
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Symbol of LED & photodiode


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Description : Draw symbol of LED and explain it’s working principle.

Answer : Construction of LED: The basic structure of LED is shown in fig.(a). The active region exists between the p and n regions. The light emerges from the active side in all the directions when electron hole-pairs ... fig.(c). In this way an LED emits light. This is the principle of operation of LED.

Description : What is photodiode? Draw the symbol and explain operation of photodiode. 

Answer : A photodiode is a light detector that converts light into an electrical current. A photodiode is a semi-conductor device, with a p-n junction and an intrinsic layer between p and n layers ... current is independent of reverse bias voltage. Reverse current is mostly depends on the light intensity.

Description : Define resistor and draw symbol of variable resistor.

Answer : Resistor: A resistor is an electrical component that limits or regulates the flow of electrical current in an electronic circuit. Symbol of variable resistor:   

Description : Draw & explain operation of phase detector.

Answer : In phase detector, the op-Amp basically acts as a zero crossing detector. If a sine wave is applied at the i/p, we get square wave at the op-Amp o/p (at point ... to two channel of the CRO. The time duration between the pulses corresponding to voltages represent the phase between them. 

Description : Analyze the effect of supply voltage on performance of LED as regards current, Lumen output, efficacy and life. 

Answer : 1) Effect on Current:- In LED current depends upon supply voltage, if voltage get changes then current also change but this change in current will be control by resistors which are connected in series.  2) ...   4) Effect on Life:- If supply voltage is not stable then life of LED get reduced.