JNTU Hyderabad
JNTU Hyderabad B.Tech II Year ANALOG ELECTRONICS Previous Question Paper (August/September - 2022 - R16)
Answer any five questions. All questions carry equal marks.
Main
Answer the following:
What is the working principle of CE amplifier? Mention its applications. Consider a single stage CE amplifier with RS = 1K and RL = 1.2K. Using typical values of h-parameters find Ai, AV, Ri and Ro.
Answer
The Common Emitter (CE) amplifier operates on the principle of current-controlled voltage amplification. A small base current variation causes a large collector current variation due to the transistor's current gain (β), which flows through a load resistor to produce an amplified voltage output. It provides a 180-degree phase shift between input and output.
Applications:
- Used as a voltage amplifier in audio frequency stages.
- Employed in radio frequency (RF) receivers for signal amplification.
- Used as a building block in multi-stage amplifier designs.
Calculation:
Typical h-parameters for a CE configuration: hie = 1.1 KΩ, hfe = 50, hre = 2.5 × 10-4, hoe = 25 µA/V. Given RS = 1 KΩ, RL = 1.2 KΩ.
Draw the circuit of two stage R-C coupled transistor amplifier and explain its working.
Answer
A two-stage R-C coupled amplifier consists of two CE amplifier stages connected in cascade using a coupling capacitor (CC) and a biasing network. The capacitor blocks the DC component of the first stage from reaching the base of the second stage while allowing the AC signal to pass.
Working:
- The input signal is applied to the base of the first transistor.
- The amplified signal at the collector of the first transistor is coupled to the base of the second transistor via the coupling capacitor.
- The second stage provides further amplification.
- The R-C network (resistors for biasing and capacitors for coupling/bypass) ensures stable operation and frequency response.
- The total gain of the system is the product of the individual gains of the two stages (Atotal = Av1 × Av2).
Answer the following:
List out the characteristics of emitter follower amplifier. For the emitter follower with RS = 0.5 K and RL = 5K, calculate AI, Ri, AV, AVS and Ro. Assume hfe = 50, hie = 1K, hoe = 25μA/V.
Answer
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Discuss about Darlington pair circuit and mention its purpose.
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Answer the following:
The h-parameters of a transistor at IC = 8mA, VCE = 10V, and at room temperature are hie = 1K, hoe = 2 × 10-5 A/V, hfe = 50, hre = 2.5 × 10-4. At the same operating point, fT = 60 MHz, and Cob = 2PF. Compute the values of hybrid-π parameters.
Answer
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How is the High frequency gain of a single stage amplifier dependent on frequencies f1 and f2?
Answer
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Answer the following:
Prove that in Hybrid-π model, the diffusion capacitance is proportional to emitter bias current.
Answer
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Define fT and what is its physical significance? If a silicon p-n-p transistor has fT = 400MHz. What is the base thickness? [Assume Diffusion constant as 13 cm2/sec]
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Answer the following:
Define and compare the performance of FET amplifier with BJT amplifier.
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Derive expression for AV and Ro for common gate amplifier.
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Answer the following:
Draw and explain the CS amplifier with current source load. Derive an expression for AV.
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Discuss the input and output characteristics of a folded cascade amplifier with NMOS input.
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Answer the following:
Explain with the help of mathematical expressions, how the negative feedback in amplifiers increases amplifier bandwidth and reduces distortion in amplifiers?
Answer
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In a transistorized Hartley oscillator, the two inductances are 2mH and 20μH while the frequency is to be changed from 950 KHz to 2050 KHz. Calculate the range over which the capacitor is to be varied.
Answer
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Answer the following:
Design a class B power amplifier to deliver 25 W to a load resistor RL=8 Ω using transformer coupling, Vm=VCC=25 V. Assume reasonable data where ever necessary.
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Draw the circuit of double-tuned transformer-coupled amplifier. Discuss the nature of responses of the amplifier for different values of KQ=1; KQ>1 and KQ<1.
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