This document provides an overview of transistors, including: - Transistors have three regions - the emitter, base, and collector. The base is thinner than the emitter and collector. - Transistors allow for faithful amplification, maintaining the shape of a weak signal as it is strengthened. Proper biasing of the base-emitter and collector-emitter voltages is needed. - Transistor biasing ensures the base-emitter junction is forward biased and collector-base junction is reverse biased during signal application. Stabilization is also needed to make the operating point independent of temperature or parameter variations.

1. WELCOME TO OUR PRESENTATION
আর হ্যা, অবশ্যই আইডি কািড সাথে ডিথে আসবা৷ ✌
Electrical Device and Circuit

2. TRANSISTOR
A transistor consists of two pn junctions formed by *sandwiching either
p-type or n-type semiconductor between a pair of opposite types.
Accordingly ; there are two types of transistors, namely;
(i) n-p-n transistor (ii) p-n-p transistor

3. SOME FACTS ABOUT THE TRANSISTOR
(i) The transistor has three regions, namely ; emitter, base and collector. The base is
much thinner than the emitter while collector is wider than both. However, for the
sake of convenience, it is customary to show emitter and collector to be of equal
size.
(ii) The emitter is heavily doped so that it can inject a large number of charge carriers
(electrons or holes) into the base. The base is lightly doped and very thin ; it
passes most of the emitter injected charge carriers to the collector. The collector is
moderately doped.

4. ADVANTAGES
• No cathode heater reducing power consumption, eliminating delay as tube heaters warm
up, and immune from cathode poisoning and depletion.
• Very small size and weight, reducing equipment size.
• large numbers of extremely small transistors can be manufactured as a single integrated
circuit.
• Low operating voltages compatible with batteries of only a few cells.
• Circuits with greater energy efficiency are usually possible. For low-power applications
in particular, energy consumption can be very much less than for tubes;
• Complementary devices available, providing design flexibility including complementary-
symmetry circuits, not possible with vacuum tubes.
• Very low sensitivity to mechanical shock and vibration, providing physical ruggedness
and virtually eliminating shock-induced spurious signals.
• Not susceptible to breakage of a glass envelope, leakage, outgassing, and other physical
damage.

5. FAITHFUL AMPLIFICATION
The process of raising the strength of a weak signal without any change in
its general shape is known as faithful amplification.

6. CONDITIONS FOR FAITHFUL
AMPLIFICATION
i. Proper zero signal collector current
ii. Minimum proper base-emitter voltage (VBE) at any instant
iii.Minimum proper collector-emitter voltage (VCE) at any
instant

7. TRANSISTOR BIASING
The proper flow of zero signal collector current and the maintenance of proper
collector-emitter voltage during the passage of signal is known as transistor
biasing.
Biasing ensures base-emitter junction is properly forward biased and collector-
base junction is properly reverse biased during the application of signal.

8. The process of making operating point independent of temperature changes or
variations in transistor parameters is known as stabilisation.
Stabilisation
Why should we need stabilization???
i. Temperature dependence of I
ii. Individual variations
iii. Thermal runaway
c

9. METHODS OF TRANSISTOR BIASING
(i) Base resistor method
(ii) Emitter bias method
(iii) Biasing with collector-feedback resistor
(iv) Voltage-divider bias

10. BASE RESISTOR METHOD
1. Circuit analysis
2. Stability factor
3. Advantages
4. Disadvantages

11. VOLTAGE DIVIDER BIAS METHOD
1. Circuit Analysis
2. Stability Factor
3. Advantages
4. Disadvantages

12. THE END