Chapter 2.1 Diode application Flashcards
Learn how to use a voltage to cause the diode to conduct current in one direction and block it in the other direction. This process is called biasing.
Define a diode.
A diode is a semi-conductor device with a single on junction and metal connections to leads. It has the ability to pass current in only one direction.
The type of material of a diode?
Semi-conductor
The example of semi-conductor a diode use.
A diode usually use a Silicon.
What is the p region called?
Anode
What is the n region called?
Cathode
What are the regions connected to?
To the conductive terminal
Draw the basic structure and schematic symbol of a diode.
Draw it on a paper and make sure you know all the labels.
What is a semi-conductor?
Semi-conductors are between conductors and insulators in their ability to conduct electricity.
What do you call the region that is between the pn junction?
Depletion region
Name the examples of Typical Diode packages.
DO - 14 , DO - 21 ,60 - 01
Marked by a band, a tab or some other feature.
Cathode
What shows the typical diode packages surface mounting on a printed circuit board?
Surface - Mount Diode Packages
Types of Surface - Mount Diode Packages
SOT, SMA and SOD
What is an SOT type?
The SOT type is a
three-terminal package in which there are either one or two diodes.
Name the L- shaped Diode Package.
SMA
Name the Gull-wing shaped leads Package .
The SOD and SOT packages
Define Forward-bias.
Forward bias is the condition that allows
current through the pn junction.
What does it mean to bias a diode.
To bias a diode, you apply a dc voltage across it
Another term for DC voltage source
An external bias voltage
What is the external bias voltage designed as?
V bias
Explain why a series resistor is necessary when a diode is forward-biased.
The resistor limits the forward cur-
rent to a value that will not damage the diode
Explain how to forward-bias a diode.
The first requirement is that the negative side of VBIAS is con-
nected to the n region of the diode and the positive side is connected to the p region.
The Second Requirement is that the bias voltage, VBIAS,
must be greater than the barrier potential.
What are the two conditions under which a diode is operated?
forward bias and reverse bias
Explain The Effect of Forward Bias on the Depletion Region
As more electrons flow into the
depletion region, the number of positive ions is reduced. As more holes effectively flow
into the depletion region on the other side of the pn junction, the number of negative ions
is reduced. This reduction in positive and negative ions during forward bias causes the de-
pletion region to narrow.
Define barrier potential.
The electric field
between the positive and negative ions in the depletion region on either side of the junction
creates an “energy hill” that prevents free electrons from diffusing across the junction at
equilibrium.
Effect of the Barrier Potential During Forward Bias
When a diode isforward-biased, the externalbiasvoltage provides energy to the free electrons so that they can overcome thebarrierpotential. Now, these electrons give up an amount of energy equal to thebarrierpotentialwhen they will cross the depletion region.
Define dynamic resistance
The internal resistance which is usually ignored since it’s very small.
Define the Reverse bias
Reverse bias is the condition that essentially prevents current through the diode.
Define avalanche effect as applied to diodes.
The multiplication of the conduction with a high reverse bias voltage
FORWARD BIAS: PERMITS MAJORITY-CARRIER CURRENT
■ Bias voltage connections: positive to anode (A); negative to cathode (K).
■ The bias voltage must be greater than the barrier potential.
■ Barrier potential: 0.7 V for silicon.
■ Majority carriers provide the forward current.
■ The depletion region narrows.
REVERSE BIAS: PREVENTS MAJORITY-CARRIER CURRENT
■ Bias voltage connections: positive to cathode (K); negative to anode (A).
■ The bias voltage must be less than the breakdown voltage.
■ There is no majority carrier current after transition time.
■ Minority carriers provide a negligibly small reverse current.
■ The depletion region widens.
What would you expect to see displayed on an oscilloscope connected across RL in the limiter
The diode is forward-biased and conducts when the input voltage goes below -0.7V so for the negative limiter determine the peak output voltage across RL. Vp(out) = (RL/R1+RL)Vp(in)
When does reverse breakdown occur in a diode?
When it exceeds the breakdown voltage of the diode
