Title BASIC ELECTRONICS.pdf ✅

LECTURERS NOTES ON BASIC ELECTRONICS (1ST SEM/2ND SEM) DEPARTMENT OF ELECTRONICS AND COMMUNICATION
MODULE-I INTRODUCTION TO ELECTRONICS: Electronics is the branch of science and engineering dealing with the theoty and use of a class of devices in which electrons are transported through a vacuum, gas or semiconductor. Signals: It contains information about a variety of things and activities. Example - Voice of the radio announcer, weather information Analog Signal: The signal magnitude can be represented at any instant of time by a sequence of numbers. Discrete Signal: It is a sequence of numbers that represent the magnitudes of the successive signal samples. Digital Signal: Signal is in the form of 0 and 1. Frequency Spectrum of Signal: Any arbitrary signal is characterized by its frequency spectrum. The signal is represented in frequency domain. Fourier series: It is an expansion of periodic signal as a linear combination of sine and cosine with different frequencies and amplitudes. It is applied to periodic signals. Fourier transform: Fourier transform can be applied to aperiodic signals to find the frequency spectrum.
Low Pass Filter: · Filter that passes low frequency components of a signal but rejects the high frequency components of a signal is called as low pass filter. · Filters designed with passive components (Resistor, capacitor, inductor) are called as passive filters. Behaviour of capacitor to frequency can be described as follows For f=0 (Low frequency) capacitive reactance of capacitor Xc= I fC V 2p 1 = =∞, So it acts as a open circuit For f=∞ (High Frequency) capacitive reactance of capacitor Xc= I fC V 2p 1 = =0So it acts as a short circuit Operation For low frequency since capacitor is open circuited, current flowing in the circuit is zero. So the output voltage vout= vin For high frequency since capacitor is short circuited, the output voltage across a short is zero So the output voltage vout= 0 The frequency response curve can be shown as below
Calculation of cutoff frequency: vout= C C R X X + vin vout = 2 C2 C R X X + vin If R=Xc Vout= 2 1 vin=0.707 vin At the frequency of which R=Xc, the output will be 70.7% of the input. Xc=R= 2pfC 1 Cutoff frequency fc= 2pRC 1 LPF as Integrator: · Output voltage (current) is directly proportional to the integration of the input voltage(current) · The time constant RC of the circuit should be very large as compared to the time period of the input wave. · The value of R should be 10 or more times larger than Xc. For high frequencies the capacitor has insufficient to charge up, its voltage is small. So the voltage across the resistor is approximately equal to the input voltage. vin=VR i= R v R VR in = The charge q on the capacitor at any instant is q= Ú idt output voltage vout= vc= v dt C RC idt C q in Ú Ú = = 1 High Pass Filter: · Filter that blocks low frequency components of a signal but passes the high frequency components of a signal is called as high pass filter. · Filters designed with passive components (resistor, capacitor, inductor) are called as passive filters.