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Microelectronics Question Paper - May 19 - Electronics And Telecomm (Semester 5) - Mumbai University (MU)

## Microelectronics - May 19

### Electronics And Telecomm (Semester 5)

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.

**1.a.**Compare constant voltage scaling and full voltage scaling.

**1.b.**Compare single ended and differential power amplifiers.

**1.c.**Why folded cascode is very popular building block in CMOS amplifier? Explain its advantages over double cascade.

**1.d.**Derive output resistance of MOS current source.

**1.e.**What are the advantages of active load?

**2.a.**Design an NMOS current source to provide a bias current of $I_{Q}=100 \mu A$ and an output resistance greater than 20 $\mathrm{M} \Omega$ . The reference current is to be $I_{\text {ref}}=150 \mu A$ . The circuit is to be biased at $\pm 3.3 \mathrm{V}$ and the voltage at the drain of the current source transistor is to be no smaller than $-2.2 \mathrm{V}$ . The minimum width to length ratio of transistor is to be unity.

**2.b.**Explain cascode current mirror in detail.

**3.a.**For CS amplifier with current source load find intrinsic gain $A_o$ and explain the effect of output resistance on gain.

**3.b.**For CS stage with resistive load amplifier prove that Gain $=-g_{m} r_{d}$

**3.c.**Compare double cascade with folded cascade.

**4.a.**Explain PMOS fabrication process with suitable diagrams.

**4.b.**Explain with proper diagram CLASS F power amplifier.

**5.a.**Explain in detail fabrication of transformer.

**5.b.**Explain short channel effects in MOSFET.

**6.a.**Explain DC transfer characteristics of MOS differential amplifier.

**6.b.**Calculate the DC characteristics of MOSFET differential amplifier shown in Fig .6$(b)$ the transistor parameters are $k_{n 1}=k_{n 2}=0.1 \frac{\mathrm{mA}}{\mathrm{v}^{2}}, k_{n 3}=k_{n 4}=0.3 \frac{\mathrm{m} A}{\mathrm{v}^{2}},$ and for all transistor $\lambda=0$ and $V_{\mathrm{tn}}=1 \mathrm{V}$ . Determine the maximum range of common-mode input voltage.

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