Comparison on devises

Comparison between FET & BJT

FET symbols

FET is a Field Effect Transistor.	BJT is Bi-polar Junction Transistor.
F ET does not suffer from minority carrier storage effects.	BJT suffers from minority carrier storage effects.
FET is a uni polar device. i.e the current conduction due to majority charge carriers only.	BJT is a Bi polar device. i.e The current  conduction is due to majority and minority charge carriers.
FET  has no junctions.	BJT has two junctions.
There are two types of FET’s .  They are 1. N-Channel FET 2. P-Channel FET	There are two types  of Transistors. They are 1. N-P-N Transistor. 2. P-N-P Transistor.
FET  has very high input resistance  ( i.e 100MΩ ) .	BJT has very low input impedance.
The noise level in a FET is comparatively lower than that in a BJT.	The noise level of BJT is high , when compared t FET.
FET amplifiers  have low  gain band width Product.	BJT amplifiers have high gain band width product , when compared to FET.
FET is a Voltage-Controlled device.	BJT is a Current-Controlled device.
It has a negative temperature co-efficient at high current levels.	It has a positive temperature co-efficient at high current levels.
FET’s are much easier to fabricate .	BJT is not much suitable than FET to fabricate in IC’s.
They occupy less space than BJT.	BJT occupy more space than FET.
FET has higher switching speeds and cut-off frequencies.	BJT has lower switching speed and cut-off frequencies.
FET is used as a buffer, RF amplifier, TV receivers, oscillator circuits, digital circuits etc….	BJT is used as a switches, amplifiers, communication, digital circuits, oscillator      circuits, buffers etc…….

 Difference between Depletion MOSFET &  Ehancement MOSFET

E-MOSFET	D-MOSFET
This will work with positive Gate Voltage	This will work with negative and zero gate voltage
At zero gate voltage the channel conductance is zero. i.e There is no conducting path.	At zero gate voltage, the channel conducting path is exist.
At zero gate voltage, ID=0 which is independent of VDS.	At zero gate voltage, ID has some value, this value depends upon VDS
Minimum threshold voltage is needed for the flow of drain current to start.	Depletion MOSFET conducts at 0 volt.
In symbol there will be a broken channel between S to D terminals. There is no channel in this type to conduct.	In symbol there will be no broken channel between S to D terminals. There is a channel in this type to Conduct.
It prefers positive voltage to conduct.	It  less prefers positive voltage to conduct.
It contains leakage current	It does not have any kind of leakage current.
Its operations are opposite to Depletion MOSFET	Its operations are opposite to Enhancement MOSFET
In enhancement MOSFET ,channel does not exist initially and is created by applying a voltage to Gate terminal.	In depletion MOSFET, channel is fabricated permanently at the time of construction of MOSFET.
Normally known as OFF transistors.	Normally known as ON transistors.

  Comparison between Photo diode and Photo transistor

PHOTO TRANSISTOR

Photo diode	Photo transistor
It is more responsive to incident light than photo transistor.	It is not as more responsive to incident light than photo diode.
It has more linear response than photo transistor	It has not more linear response than photo diode.
It passes less current.	It passes more current than photo diode.
It consumes more less current.	It consumes more current than photo diode.
Less dark current than photo transistor.	Higher dark current than photo diode.
It can be constructed by a reverse bias P-N junction diode.	It can be constructed by BJT or FET
It is used in light detectors, demodulators and encoders.	It is used as light sensitive device, light measurement, opto-coupler.
Less sensitivity  and its output response  is fast	More sensitivity and its output response is slow.
It is used for light operated switches	It is used in light detection systems
It generates current	It generates current and voltage

 Comparison between LCD and LED

LED	LCD
LED means light emitting diode	LCD means liquid crystal device
Requires high power. So used for external interface circuit, when driven from IC’s.	Can be driven directly from IC-Chips.
Good brightness level.	Moderate brightness level.
Operating Temp range is -40 to 850C	Operating Temp range is -20 to 600C.
Life time is nearly [20 years (or) 1,00,000 Hrs]	Life time is limited [50,000 Hrs]
Emits light in red, orange, yellow, green, blue& white	Invisible in darkness requires external illumination.
Response time is 50 to 500 ns	Has a slow decay time response time is 50 to 200 ms
Viewing angle 1500	Viewing angle 1000
Operating voltage range is 1.5 to 5 V d.c	Operating voltage range is 3 to 20V A.C
Used in shop watches, Display devices, all toys, T.V & Computer Screens.	Used in Display devices Eg:- T.V & Computer Screens.
Designed by S.C device.	Designed by liquid Crystal material.
Consumes  more power	Essentially acts as a capacitor & consumes very less power
They are small in size and light in weight.	They are large in size
They can be switched ON & OFF at a fast speed.	They can be switched ON & OFF are quite large time.
It requires 10-250 m W power per digit.	It requires 10-200 µW power per digit.