Comprehensive notes for Chapter 18 Electronics. Covers PN Junction, Rectification, LED, Photodiode, Transistors (BJT), Operational Amplifiers (Op-Amp), and Digital Logic Gates.
P-N Junction: Formed by doping one half of crystal with trivalent and other with pentavalent impurity. Depletion Region: Charge-less region around junction.
Forward Bias: P connected to +ve, N to -ve. Current flows.
Reverse Bias: P connected to -ve, N to +ve. No current (except leakage).
Conversion of AC to DC. Half Wave: Conducts only during positive half cycle. Full Wave (Bridge): Conducts during both cycles using 4 diodes.
LED: Emits light when forward biased (GaAs). Used in displays.
Photodiode: Detected light when reverse biased. Resistance decreases with light intensity.
Photovoltaic Cell: Converts light to electricity. No external bias needed.
Structure: Bipolar Junction Transistor (BJT). Three regions: Emitter, Base, Collector. Types: PNP, NPN.
Current Equation: $$ I_E = I_B + I_C $$. Current Gain $$ \beta = I_C / I_B $$.
As Amplifier: Uses small base current to control large collector current. $$ V_{out} = -\beta I_B R_C $$. Phase shift of 180 degrees.
As Switch: ON (Saturation) and OFF (Cut-off) states.
High gain electronic amplifier with two inputs: Inverting (-) and Non-Inverting (+).
Characters: High input resistance, Low output resistance, High open loop gain ($$ 10^5 $$).
Inverting Amplifier Gain: $$ G = -R_2 / R_1 $$
Non-Inverting Amplifier Gain: $$ G = 1 + R_2 / R_1 $$
Comparator: Compares two voltages. Used in Night Switch (LDR circuit).
Deals with quantities having two discrete states: High (1) and Low (0). Boolean Algebra: Mathematical tool for digital circuits.