Electrironic device

2. The width of the depletion region increases with the
increase in voltage only up to a certain value or
point.
If the reverse voltage applied on the p-n junction
diode is increased beyond that value or point, the
junction breaks down and allows a large reverse
current.
At this point, a small increase in the voltage will
rapidly increase the electric current.

3. When the reverse voltage reaches breakdown voltage in normal PN junction diode, the current
through the junction and the power dissipated at the junction will be high. Such an operation is
destructive and the diode gets damaged.
Whereas diodes can be designed with adequate power dissipation capabilities to operate in the
breakdown region

4. Zener Diode
A Zener diode is a silicon semiconductor
device that permits current to flow in either a
forward or reverse direction. The diode
consists of a special, heavily doped p-n
junction, designed to conduct in the reverse
direction when a certain specified voltage is
reached.
Zener diodes are used for voltage regulation,
switching applications and clipper circuits.

5. Varactor Diode
As the capacitance is inversely proportional to the
distance between the plates the transition capacitance
CT varies inversely with the reverse voltage
Consequently, an increase in reverse bias voltage
will result in an increase in the depletion region width and
a subsequent decrease in transition capacitance CT.
At zero volt, the varactor depletion region W is small and
the capacitance is large at approximately 600 pF.
When the reverse bias voltage across the varactor is 15
V, the capacitance is 30 pF
The varactor diodes are used in FM radio and TV
receivers, AFC circuits, self adjusting bridge circuits and
adjustable bandpass filters

6. Tunnel Diode
Exhibits negative resistance under low forward
bias conditions
The width of the junction barrier varies
inversely as the square root of the impurity
concentration
the electrons will penetrate
through the thin junction rather
than surmounting them
A – Peak Voltage
B Velley Voltage
Peak Current 2 mA
P to V Current : 10m A
Negative
resistance

7. Schottky Diode

8. A transistor is a device that regulates current or voltage flow and acts as a switch or gate for electronic
signals
Unipolar : Current Conduction only by one type of charge carriers – Majority
Bipolar : Current Conduction by both type of charge carriers – Majority / Minority
Advantages of BJT
1. Low operating voltage
2. Higher efficiency
Transistor

9. Types of BJT
Two diode Transistor Analogy
Transistor Symbol
Transistor Construction

10. Biasing - NPN
Biasing - PNP
BJT Biasing
IE = – (IC + IB)
IE = (IC + IB)

11. Configuration in BJT
Common Base Common Emitter
Common Collector
CB
This is also called grounded base configuration.
In this configuration, emitter is the input terminal, collector is the output
terminal and base is the common terminal.
CE
This is also called grounded emitter configuration.
In this configuration, base is the input terminal, collector is the output
terminal and emitter is the common terminal.
CC
This is also called grounded collector configuration.
In this configuration, base is the input terminal, emitter is the output
terminal and collector is the common terminal

12. Compare the performance of Transistor in different configuration

13. Draw the two-port model of a CB CONFIGURATION of BJT. Obtain the expressions for input impedance, current gain,
voltage gain and output admittance