Tunnel Diode OLED Varactor Diode

1. Assignment 1
Made by –
Jannet Mathew 17BEC100__
Mahesh Kumar 17BEC10025
Nikhil Singh Hada 17BEE10029
Shivani Gupta 17BEC10031
Vikram Pratap Singh Sengar 17BEC10035
Vishnu Narayanan K 17BEE10020

2. Tunnel Diode

3. A Tunnel diode is a heavily doped p-n junction
diode in which the electric current decreases as
the voltage increases.
In tunnel diode, electric current is caused by
“Tunneling”. The tunnel diode is used as a very
fast switching device in computers. It is also used
in high-frequency oscillators and amplifiers.
The circuit symbol of tunnel diode is shown in the
below figure. In tunnel diode, the p-type
semiconductor act as an anode and the n-type
semiconductor act as a cathode.


4. A tunnel diode is also known as Esaki diode which
is named after Leo Esaki for his work on the
tunneling effect. The operation of tunnel diode
depends on the quantum mechanics principle
known as “Tunneling”. In electronics, tunneling
means a direct flow of electrons across the small
depletion region from n-side conduction band into
the p-side valence band.
 The germanium material is commonly used to make
the tunnel diodes. They are also made from other
types of materials such as gallium arsenide, gallium
antimonide, and silicon.

5. OLED(Organic Light Emitting Diode)

6.  An organic light-emitting diode (OLED) is a light-emitting
diode (LED) in which the emissive electroluminescent layer is a film
of organic compound that emits light in response to an electric
current. This layer of organic semiconductor is situated between two
electrodes; typically, at least one of these electrodes is transparent.
OLEDs are used to create digital displays in devices such
as television screens, computer monitors, portable systems such
as mobile phones, handheld game consoles and PDAs. A major area
of research is the development of white OLED devices for use
in solid-state lighting applications.
 There are two main families of OLED: those based on small
molecules and those employing polymers. Adding mobile ions to an
OLED creates a light-emitting electrochemical cell (LEC) which has a
slightly different mode of operation. An OLED display can be driven
with a passive-matrix (PMOLED) or active-matrix (AMOLED) control
scheme. In the PMOLED scheme, each row (and line) in the display is
controlled sequentially, one by one,[4] whereas AMOLED control uses
a thin-film transistor backplane to directly access and switch each
individual pixel on or off, allowing for higher resolution and larger
display sizes.

7.  A typical OLED is composed of a layer of organic materials
situated between two electrodes, the anode and cathode, all
deposited on a substrate. The organic molecules are electrically
conductive as a result of delocalization of pi electrons caused
by conjugation over part or all of the molecule. These materials
have conductivity levels ranging from insulators to conductors,
and are therefore considered organic semiconductors. The
highest occupied and lowest unoccupied molecular orbitals
(HOMO and LUMO) of organic semiconductors are analogous to
the valence and conduction bands of inorganic semiconductors.
Schematic of a bilayer OLED: 1. Cathode
(−), 2. Emissive Layer, 3. Emission of
radiation, 4. Conductive Layer, 5. Anode
(+)

8. Varactor Diode

9.  A tuning diode, also known as a varactor diode, variable
capacitance diode, varicap diode or variable reactance diode, is a
diode that has a variable capacitance which is a function of the
voltage that is impressed on its terminals. Tuning / varactor diodes
are operated reverse-biased, and therefore no current flows.
However, since the thickness of the depletion zone varies with the
applied bias voltage, the capacitance of the diode can be made to
vary. Usually, the capacitance is inversely proportional to the
depletion region thickness and the depletion region thickness is
proportional to the square root of the applied voltage. Therefore,
the capacitance is inversely proportional to the square root of the
voltage applied to the diode.
 The most common sizes for nominal diode capacitance are 22 pF
and 33 pF. We also carry tuning / varactor diodes with nominal
diode capacitance up to 100 pF. Minimum breakdown voltage can
be up to 30 V, with the most common size being 25 V.

10. Applications
 Tuning / varactor diodes are often used in RF design. They
provide a way of varying the capacitance within a circuit by
applying a control voltage. Due to this capability, tuning /
varactor diodes are widely used in the RF industry. They can
be found in voltage controlled oscillators such as in a phase
locked loop and are used in almost all radio, cellular and
wireless receivers. They can also be found in RF filters for
tuning purposes (for example, as tuners of television sets to
electronically tune the receiver to different stations),
parametric amplifiers, parametric oscillators and frequency
synthesizers.

11. Thank you