Question

2. Sketch Vout VS Vin and Vout if Vin-10sin(2TT60t) for each of the following circuits. You may assume that the forward diode drops for the diodes equals zero Vout s v out Vin 5 V Vout out 3. Repeat problem 2 but with forward diode drops equal to 0.7 V 4. What are the primary mechanisms for current flow in a. A forward biased diode. b. A reverse biased diode not in breakdown. c. A reverse biased diode in breakdown 5. Why is the forward biased voltage for a typical red LED so much greater than the forward biased voltage for a typical silicon diode? 6. What is the depletion region in a diode and why does it form?

Answer 1

Answen 2 ven in tlo ーラ·t 七 닌0 t) lo 0 to O- 7 ラも o门 -lov 3) Vour -SV. 十ちv -0-7 Vau (5) tio lov 0-7也

See the characteristics of the diode for the answer of question 4

NIP athode (K) Anode (A) +I (mA) Forward Current Forward Bias Conventional Current Flow Reverse Breakdown Voltage knee Reverse Voltage Forward Voltage 50mA Germanium 20mA Silicon 0.3v Germaniunm 0.7v Silicon Zene Breakdown or Avalanche Region Rever se Bias Reverse Current

in the characteristics all the 3 mode are shown.

Answer 5-

Red LED is made up of GaAsP (Gallium arsenide phosphate) it have many impurity so the forward biasing voltage increases but simple silicon diode has low biasing voltage.

6.

Formation of Depletion Layer in Diode There is greater concentration of holes in P-region and electrons in N-region. This difference in concentration establishes a density mismatch across the junction resulting in majority carrier diffusion Holes diffuse from P to N and electrons from N to P regions causing the recombination PN Juntion Diffusion Deplition Layer Formation of Depletion Layer In PN Junction This recombination of electrons and holes produces a narrow region at junction called depletion layer Potential Barrier As the depletion layer built up a different of potential appears across the junction this difference of potential at junction is called potential barrier. The value of potential barrier VB is 0.3 volt for germanium and 0.7 Volts for Silicon orward Blas When a P-region of a semiconductor diode is connected with the positive terminal of battery and the N-region with negative terminal of the battery then the PN Junction is said to be forward biased

Reverse Bias When a P-region of a semiconductor diode is connected with the negative terminal and N-region with the positive terminal of the battery then the PN Junction is said to be reverse biased In reverse bias the holes are attracted toward the negative terminal of the battery and the electrons are attracted towards the positive terminal of the battery causing the majority carrier both holes and electrons move away form the unction and each other Characteristics of PN Junction Forward Bias 70 60 50 40 30 20 10 12-10 -8 -6 4 10 15 -20 25 Break Down Voltage VBR Reverse Bias mA When the diode is forward biased and the applied voltage is increased from zero hardly any current flows through the diode in beginning, because the external voltage is being oppose by the internal barrier voltage (VB) whose value is 0.7 Volt for silicon and 0.3 Volt for Germanium. It is seen that when the voltage approaches to one volt (1V)

a high forward current flows through the diode. When the diode is in reverse bias majority carrier are block and only a small current due to minority current flows through the diode. As the reverse voltage is increase from zero the reverse current very quickly reaches its maximum or saturation value lo which is known as leakage. When reverse voltage exceeds a certain value whiclh break down the the diode and huge amount of current flow through diode. This voltage is called break down voltage

Maximum Forward Current The highest current which a junction can conduct with out damaging it is called maximum forward current Peak Inverse Voltage (PIV) Peak inverse voltage PIV is the maximum reverse voltage that can be applied to the PN Junction with out damaging the junction. Maximum Power Rating It is maximum power rating is the maximum power that junction dissipate with out being over heated Applications of PN Junction Diode It is mostly used as rectifier . In Communication for modulation and demodulation

any doubt comment.