Advertisements
Advertisements
Question
The current in the forward bias is known to be more (~mA) than the current in the reverse bias (~μA). What is the reason, then, to operate the photodiode in reverse bias?
Advertisements
Solution
The photodiode always work under reverse biasing conditions although the current produced is less. This is because in reverse bias, the width of the depletion layer increases which reduces the capacitance across the junction, thereby increasing response time. The sensitivity of a photodiode is thus very high, a property that is certainly desired.
APPEARS IN
RELATED QUESTIONS
Colour of light emitted by LED depends upon__________________ .
- its forward bias
- its reverse bias
- the band gap of the material of semiconductor
- its size
Explain with the help of a diagram, how depletion region and potential barrier are formed in a junction diode.
If a small voltage is applied to a p-n junction diode, how will the barrier potential be affected when it is (i) forward biased
Write briefly the important processes that occur during the formation of p−n junction. With the help of necessary diagrams, explain the term 'barrier potential'.
Draw V − I characteristics of a p-n junction diode. Answer the following questions, giving reasons:
(i) Why is the current under reverse bias almost independent of the applied potential up to a critical voltage?
(ii) Why does the reverse current show a sudden increase at the critical voltage?
Name any semiconductor device which operates under the reverse bias in the breakdown region.
Write the important considerations which are to be taken into account while fabricating a p-n junction diode to be used as a Light Emitting Diode (LED). What should be the order of the band gap of an LED, if it is required to emit light in the visible range? Draw a circuit diagram and explain its action.
With reference to Semiconductor Physics,
Name the process that causes depletion region in a p-n junction.
What is the magnitude of the potential barrier across a Ge p-n junction?
Name the device which converts the change in intensity of illumination to change in electric current flowing through it. Plot I-V characteristics of this device for different intensities. State any two applications of this device.
Pressure P varies as P = `alpha/beta "exp" (- (alpha x)/"k"_"BT")`, where x denotes the distance, kB is the Boltzmann's constant, T is the absolute temperature and α and β are constant. The dimension of β is ______.
