Electronic Circuits-I 2022 Question Paper — Government College of Eng…
The 2022 Electronic Circuits-I previous year question paper (Government College of Engineering and Technology, Jammu), with every question and its marks.
- University: Government College of Engineering and Technology, Jammu
- Subject: Electronic Circuits-I
- Course: Electronics Circuits- I
- Branch: E&C Engineering
- Year: 2022
- Paper: end-term
- Duration: 180 minutes
- Total marks: 100
Instructions
- Attempt five questions in all, selecting at least two questions from each section.
- Use of calculator is allowed.
- Assume suitable data, wherever missing.
- Each question carries 20 marks.
Questions
Section - A
- Q1. What are the advantages of hybrid model? Develop a hybrid model of a transistor CE configuration in line with two port network. Prove that for two port network: i. $A_i = \frac{-h_f}{1 + h_o Z_L}$ ii. $Z_i = h_i - \frac{h_f h_r}{h_o + Y_L}$ iii. $A_v = A_i \frac{Z_L}{Z_i}$ iv. $Y_o = h_o - \frac{h_f h_r}{R_s + R_i}$ Where symbols have their usual meanings. State the Miller's theorem and its dual and explain its applications. [20 marks]
- Q2. Draw and explain the frequency response of a RC coupled amplifier. The transistor amplifier shown in fig.1 uses a transistor with typical h-parameter values. Calculate: i. $A_i, A_v, A_{vs}$ ii. $R_i & R_i'$ iii. $R_o$ and $R_o'$ For the circuit shown in fig. 1. [20 marks]
- Q3. What is the need of the cascading in the amplifiers? Explain the various coupling schemes used in the multistage amplifiers. Draw a two stage RC coupled amplifier and explain its operation. Discuss the effect of cascading on the bandwidth of the amplifier. A multi stage amplifiers consists of three stages, The voltage gains of the stages are 30, 50 and 80. Calculate the overall voltage gain in 'db'. [20 marks]
- Q4. Draw the hybrid-$\pi$ model and explain its components. Define the parameters $f_T$ and $f_\beta$ and prove that $f_T \approx h_{fe} f_\beta$. When a transistor is biased at 10mA, 10V, it has the following h-parameters at room temperature. $H_{ie} = 500\Omega, h_{fe} = 100, h_{re} = 10^{-4}, h_{oe} = 4 \times 10^{-5}$. It has $f_T = 50Mhz$ and $C_{ob} = 3PF$. Find the values of all hybrid-$\pi$ parameters. [20 marks]
Section - B
- Q5. Give the classification of power amplifiers. Differentiate between a voltage amplifier and a power amplifier. Draw & explain the push - pull amplifier (class A). How the harmonic distortion can be reduced in the push-pull system? Explain the advantages of push-pull class A operation. [20 marks]
- Q6. What are the properties of feedback amplifiers? Mathematically show the effect of feedback on the following topologies: i. Voltage - shunt ii. Current - series iii. Voltage series The effect need to be analysed on input resistance only. An amplifier with open loop voltage gain of $1000 \pm 100$ is available. However, we desired to build an amplifier whose gain does not vary by more than $0.1\%$. Find the required feedback ratio '$\beta$' and the corresponding closed loop voltage gain. [20 marks]
- Q7. An amplifier of 60 db gain has an output resistance $R_o = 10K$. It is required to modify its output impedance to $500\Omega$ by negative feedback. Calculate the value of the feedback factor. Also find the percentage change in the overall gain, for $10\%$ change in the gain of the internal amplifier. Draw a feedback amplifier in block diagram form and explain each block giving its function. What are the four topologies of the feedback amplifiers? Identify all the signals and transfer gains of each topology. [20 marks]
- Q8. What are the various types of distortions in any power amplifiers? Explain the harmonic distortion. Define the distortion components $D_1, D_2, D_3, D_4$ etc hence find the distortions factor D. Derive the expression for output power in terms of power delivered at fundamental frequency and distortion factor. A sinusoidal signal $Vs = 1.95 \sin 400t$ is applied to a power amplifier. The resulting output current is $I_o = 12 \sin 400t + 1.2 \sin 400t + 0.9 \sin 1200t + 0.4 \sin 1600t$. Find i. Total harmonic distortion ii. Percentage increase in power because of distortion. [20 marks]