JNTU
JNTU B.Tech II ELECTRONIC CIRCUITS Previous Question Paper (March/April - 2021 - R15)
Answer any Five Questions. All Questions Carry Equal Marks.
Main
Define various h-parameters, draw the generic hybrid parameter model of a transistor at low frequencies and also draw the hybrid models for CE, CB and CC Configurations.
Answer
The h-parameters (hybrid parameters) are defined based on the relationship between input voltage, input current, output voltage, and output current in a two-port network. The governing equations are:
The parameters are defined as follows:
- h11 (Input Impedance): V1/I1 with V2 = 0 (output short-circuited).
- h12 (Reverse Voltage Transfer Ratio): V1/V2 with I1 = 0 (input open-circuited).
- h21 (Forward Current Gain): I2/I1 with V2 = 0 (output short-circuited).
- h22 (Output Admittance): I2/V2 with I1 = 0 (input open-circuited).
The generic hybrid model consists of a series voltage source (h12V2) and input resistor (h11) at the input port, and a parallel current source (h21I1) and output conductance (h22) at the output port. For specific configurations, the parameters are denoted with a second subscript (e, b, or c):
- CE Configuration: Uses hie, hre, hfe, and hoe. The input is base current and output is collector current.
- CB Configuration: Uses hib, hrb, hfb, and hob. The input is emitter current and output is collector current.
- CC Configuration: Uses hic, hrc, hfc, and hoc. The input is base current and output is emitter current.
A negative feedback amplifier has A=100, β=0.04 and Vs=50 mV. Find:
i) Gain with feedback (Af)
ii) Output Voltage (Vo)
iii) Loop gain.
Answer
Given: A = 100, β = 0.04, Vs = 50 mV.
i) Gain with feedback (Af):
ii) Output Voltage (Vo):
iii) Loop gain:
With neat diagram, explain the concept of feedback. Also explain each block used in feedback concept.
Answer
Sign in to view the complete answer paper.
Explain the frequency response of BJT amplifier analysis at low and high frequencies.
Answer
Sign in to view the complete answer paper.
Write a short note on Miller effect capacitance.
Answer
Sign in to view the complete answer paper.
Draw the small-signal high frequency CE model of a transistor.
Answer
Sign in to view the complete answer paper.
What is the relationship between fT and fβ? Discuss the significance of fT.
Answer
Sign in to view the complete answer paper.
Explain the response of the clamping circuit when a square wave input is applied under steady state conditions.
Answer
Sign in to view the complete answer paper.
Explain the operation of Bi-stable Multivibrator with circuit diagram and wave forms.
Answer
Sign in to view the complete answer paper.
Explain the effect of diode characteristics on clamping voltage.
Answer
Sign in to view the complete answer paper.
Explain the operation of Astable Multivibrator with circuit diagram and wave forms.
Answer
Sign in to view the complete answer paper.
Explain the Class-B push pull amplifier and its advantages, with neat diagram.
Answer
Sign in to view the complete answer paper.
A series fed class-A amplifier uses a supply voltage of 10V and load resistance of 20Ώ. The A.C input voltage results in a base current of 4 mA peak. Assume β=50, RB=1KΏ. Calculate the efficiency.
Answer
Sign in to view the complete answer paper.
Define all switching times of Diode as a switch.
Answer
Sign in to view the complete answer paper.
Draw a circuit diagram to show how a BJT can be used as switch. Identify all currents and voltages, Show typical input and output voltages.
Answer
Sign in to view the complete answer paper.