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Showing posts from February, 2020

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Q1. What is detector? Draw the block diagram of a receiver of AM wave.  Solution Detection or Demodulation is the process of retrieval of information from the modulated carrier wave at the receivers end . The device used for this purpose is called a detector or a demodulator.   The block diagram of an AM wave receiver has been shown in the figure above. As the received signal from receiving antenna is a weak one, the signal is amplified by the use of an amplifier. To facilitate further processing, the carrier frequency is usually changed to a lower frequency by the use of an intermediate frequency stage (IF). After this the carrier is supplied to the detector. As the detected signal may not be strong enough to be made use of, we again amplify the detected modulating (message) signal before converting it into proper voice or video format. Q2. Briefly explain the ground wave propagation of radio waves. Solution Radiowaves in medium band of radio broadcast are ...

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Q1. Write the truth table for the combination of gates shown below Solution Q2. Draw a circuit diagram for use of NPN transistor as an amplifier in common emitter configuration. The input resistance of a transistor is 1000 Ω. On changing its base current bv 10 uA. the collector current increases bv 2  mA. If a load resistance of 5 k Ω is used in the circuit, calculate: (i) The current gain (ii) Voltage gain of the amplifier Solution   Numerical: Given R in = 1000 Ω Δ I B = 10 μA = 10 -5 A ΔI C = 2mA = 2 x 10 -3 A R out = 5 kΩ = 5 x 10 3 Ω (i) Current gain (ii) Voltage gain   Q3. Name the p-n junction diode which emits spontaneous radiations when forward biased. How do we choose the semiconductor, to be used in these diodes, if the emitted radiation is to be in the visible region? Solution The p-n junction diode, which emits spontaneous radiation when forward biased, is known as the light emitting diode or LED. The visible light is fr...