Question Paper: Electronic Devices and Circuits 1 Question Paper - May 18 - Electronics And Telecomm (Semester 3) - Mumbai University (MU)

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## Electronic Devices and Circuits 1 - May 18

### Electronics And Telecomm (Semester 3)

Total marks: 80

Total time: 3 Hours
INSTRUCTIONS

(1) Question 1 is compulsory.

(2) Attempt any **three** from the remaining questions.

(3) Draw neat diagrams wherever necessary.

**Q1) Attempt any five questions**

**1(a)**Prove that for a JFET the gate-source bias for zero temperature drift of drain current is at | Vp | = - 0.63 volts.

**1(b)**Explain the hybrid pi model of BJT.

**1(c)**Explain Zener as voltage regulator.

**1(d)**Consider a BJT has parameters $fT =500MHz$ at $IC = 1mA$, $β = 100 and Cμ = 0.3pF$. Calculate bandwidth of $fβ$ and capacitance $Cπ$ of a BJT.

**1(e)**Draw and explain small signal model of a diode.

**1(f)**Why should RC be as large as possible in the design of CE amplifier?

**2(a)**Design a voltage divider bias network using a supply of 24 V, a transistor with $β=110 $ and an operating point of $I_{CQ} = 4 mA$ and $V_{CEQ} = 8V$. Assume

$$ V_E = \frac{1}{8} V_{CC}$$

**2(b)**Explain the fabrication steps of passive elements

**2(c)**What are the important JFET parameters and define it from characteristics.

**3(a)**Design the resistors of a single stage CS amplifier for audio frequency with BFW11 with $I_{DS} = (3.3 \pm 0 .6 ) mA $ and $| A_V | = 12.$

**3(b)**Draw CS JFET amplifier with self bias circuit and derive the expression for voltage gain input impedance and output impedance.

**4(a)**Draw small signal hybrid parameter equivalent circuit for CE amplifier and define the same. What are the advantages of h parameters?

**4(b)**For the circuit shown below in Fig.4b, the transistor parameters are $V_{BE(on)} = 0.7 V$, $β = 200$ and $V_A = \infty$.

- i) Derive the expression for lower cut-off frequency (or time constant) due to input coupling capacitor.
- ii) Determine lower cut-off frequency and midband voltage gain.

**5(a)**Design an L section LC filter with full wave rectifier to meet the following specifications: The DC output voltage $V_{DC} = 220 V$, deliver $I_L = (70 \pm 20) mA$ to the resistive load and the required ripple factor is 0.04.

**5(b)**For the circuit shown below in Fig.5(b), the transistor parameters are $V_{BE(on)} = 0.7 V$, $β = 100$ and $V_A = \infty$. Determine Zi, Zo and Av.

**Q6) Short notes on: (Attempt any four)**

**6(a)**BJT high frequency equivalent circuit

**6(b)**Types of resistors and capacitors

**6(c)**Stability factors of various biasing techniques of BJT

**6(d)**Different types of filters

**6(e)**Comparison of BJT CE and JFET CS amplifier