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KNCET, TRICHY Page 1 KONGUNADU COLLEGE OF ENGINEERING AND TECHNOLOGY Tholurpatti (Po), Thottiam (Tk), Trichy (Dt) – 621 215 M.E APPLIED ELECTRONICS II SEMESTER/ I-YEAR AP 7201 Analysis and Design of Analog Integrated Circuits Two Marks Q&A Prepared by PG Student 2013 Batch
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ANALYSIS AND DESIGN OF ANALOG IC

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Page 1: ANALYSIS AND DESIGN OF ANALOG IC

KNCET, TRICHY Page 1

KONGUNADU COLLEGE OF ENGINEERING AND TECHNOLOGY

Tholurpatti (Po), Thottiam (Tk), Trichy (Dt) – 621 215

M.E APPLIED ELECTRONICS

II SEMESTER/ I-YEAR

AP 7201 Analysis and Design of Analog Integrated

Circuits

Two Marks Q&A

Prepared by PG Student 2013 Batch

Page 2: ANALYSIS AND DESIGN OF ANALOG IC

KNCET, TRICHY Page 2

UNIT-I SINGLE STAGE AMPLIFIERS

1. Draw the input output characteristic of an non linear system.

2. Write the non linear system function equations.

The non linear system function equation can be written as For a

sufficiently narrow of x

Where

Y(t) = a0 + a 1x(t) + a2x2(t)+...........+anxn(t) x1<x<x2

3. What are the types of single stage amplifiers?

Common source

Common drain

Common gate

Cascade and folded amplifiers

4. Draw the analog design octagon.

5. What are the different types of loads used in an amplifiers?

Resistive load

Diode connected load

Current source load

Triode load

Source degeneration

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6. What are the two parameters of an amplifier?

Small signal model analysis

Large signal model analysis

7. Define voltage gain.

The ratio of the output voltage to the input voltage is called as voltage gain.

Av = Vout / Vin

8. What are the two types of common source amplifiers?

Without source degeneration(no body effect)

With source degeneration( body effect)

9. Draw the circuit diagram of common source amplifier.

10. Write the small signal gain equation.

Where,

gm = un COx w/L(Vin - VTH)

11. What are the types of diode connected load?

PMOS diode connected load

NMOS diode connected load

12. What is diode connected device?

A MOSFET can operate as a small signal resistor. If its gate and drain

are shorted it is called as diode connected load

13. What are the models is to be analysed in common source stage with

source generation?

Small signal model

Lemma model

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14. Define source follower.

The common source stage can achieve high voltage gain with limited

supply voltage and the load impedance is large. If this stage is to drive a low

impedance load the buffer must be placed after an amplifier. The source

follower can operated as a voltage buffer

15. What is common gate stage?

In the common source and drain the input voltage is applied to the gate

terminal but in the common gate stage the input is applied to the source

terminal. It produces the output at the drain terminal

16.Define Cascode stage.

The combination of CS stage and CG stage is called a cascade

Topology

17. What is shielding property?

If the output node voltage is changed by the resulting change at the source

of the cascade device is much less in this the cascade transistor “shields” the

input device from voltage variations at the output

18. Draw the folded circuit diagram.

19. How do we choose sufficient accurate device?

1. Break the circuit down into a number of familiar topology

2. Concentrate on each sub circuit and use the simplest transistor model for

all the transistors

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20. Define single ended signal and differential signal.

1.It is measured with respect to a fixed potential (i.e)ground

2.It is measured between two nodes it have equal and opposite signals

21. Define differential amplifier.

The function of differential amplifier is to amplify the difference between

two signals

22. What are needs of differential amplifier?

The need of differential amplifier is assign in many physical measurements

where response from dc to many MHZ of frequency is required

23. What are all the properties of differential amplifier?

Excellent stability

High versatility

High immunity to interference signals

24. What are the advantages of differential amplifier as a building block

of the op amp?

Low cost

Easy to fabricate

Closely matched components

25. Define CMRR.

The ratio of the differential voltage gain ADM to the common mode

Voltage gain ACM.

CMRR = 20 log [ADM/ACM]

26. Define figure of merit.

The differential amplifier is to cancel or reject the noise signal that appears

as a common input signal in both the input terminals of the differential

amplifier. The figure of merit is also called as CMRR

27. Define Differential mode gain and common mode gain.

Two different signals are applied to the two transistors. The output is

v1+v2/2 the input signals are equal to both the transistor v1=v2 this is called

as common mode gain

28. What are the types of analysis used in the differential pair?

Qualitative analysis

Quantitative analysis

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29. Draw the small signal differential gain of the differential pair as a

function of the input cm level.

30. Draw the Input output characteristic curve of CS stage.

1.Resistive load 2.Diode connected load

31. Draw the input output characteristic curve of an single stage

Amplifier.

1. CS stage 2.CG stage

3. source follower 4.cascode stage

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UNIT -2 FREQUENCY RESPONSE OF AMPLIFIERS

1. State and prove the miller effect.

If the circuit of (a) is converted into circuit of (b) then Z1=Z/(1-Av) and

Z2=Z/(1-Av^-1) where Av=Vy/Vx

Proof:

The current following through Z from X to Y is equal to (Vx-Vy)/Z for

the two circuits to be equivalent, the same current must flow through Z1.

Vx-Vy/Z=vx/Z1

Z1=Z/1-(Vy/Vx)

Similarly,

Z2= Z/1-(Vy/Vx)

2. Write the transfer function of a cascade of amplifiers by the

association of poles with nodes.

The transfer function is written as,

(Vout/vin)(s)=(A1/1+RsCins)(A2/1+r1CnS)(1/1+R2cpS)

Where,

Cp - load capacitance

Cn – input capacitance

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3. Write the transfer function of common source stage.

The transfer function is written as,

(Vout/Vin)(s)= (-gmRD)/(1+(s/win))(1+(s/wout))

4. Write the transfer function of source follower.

The transfer function is written as,

5. Mention the input and the output impedance of source follower.

6. Write the transfer function of a common gate stage

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7. Mention the pole frequency of common gate stage.

The pole frequency of common gate stage is,

Wp,in = 1/ (Rs|| (1/gm+gmb)Cin)

8. Write the input impedance of a cascade stage.

9. Draw the high frequency model of a cascade stage.

10. Explain the lemma model.

These circuits are equally at low frequencies if Vn^2=In^2/gm^2 and the circuits are driven by a finite impedance.

This Lemma suggests that the noise source can be transformed from a drain to source current to a gate series voltage for qzs.

11. Define the expression of noise bandwidth.

Where Bn is called “noise bandwidth”

V0 is the low frequency noise.

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12. Define power spectral density.

The power spectral density Sx(f) of a noise waveform x(t) is defined as

the average power carried by x(t) in a one – hertz bandwidth around f.

The spectrum shows how much power the signal carries at each

frequency.

13. What is meant by white noise spectrum?

The white spectrum is also called as white noise. The PSD displays the

same value at all frequencies.

The White noise doesnot exist because the total area under the power

spectral density i.e the total power carried by the noise, is infinite any noise

spectrum that is flat in the band of interest is usually called white.

14. Which theorem is used to analyzing the effect of noise in the

circuits?

If a signal with spectrum Sx(f) is applied to the linear time –invariant

system with the transfer function H(s),then the output spectrum is given by,

Sy(f)=Sx(f)|H(f)|^2

Where,

h(f)=H(s)=H(s=2*3.14jf)

15. Define the probability density function of x(t).

The probability density function (PDF), the distribution of X(t) is defined as,

Px(x)dx=probability of x<X<x+dx,

Where,

X is the Measured value of x(t)at some point in time.

16. Define Gaussian pdf.

The gaussian PDF is defined as,

Where,

Sigma and M are the standard deviation and Mean of the Distribution.

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UNIT-3 OPERATIONAL AMPLIFIERS

1. What are the four elements in the feedback system?

The feed forward amplifier A means of sensing the output The feedback network

A means of generating the feedback error 2. What are the properties of feedback circuits?

Gain desensitization

Terminal impedance modification

Bandwidth modification

3. Draw the general feedback system and its equations.

4. What are the types of amplifiers?

Voltage amplifier Trans impedance amplifier Transconductance amplifier Current amplifier

5. What are the different properties of four amplifiers?

A circuit sensing a voltage must exhibit a high input impedance (as a

voltmeter), whereas those sensing a current must provide a low input

impedance (as a current meter).

A circuit generating a voltage must exhibit a low output impedance (as

a voltage source) while those generating a current must provide a high

output impedance (as a current source).

6. What are the feedback topologies?

Voltage-voltage feedback

Current –voltage feedback

Voltage –current feedback

Current-current feedback

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7. Draw and write the equations for two port network models.

For the Z model For the Y model

8. What are the parameters required for op-amp?

Gain Large signal BW Output swing Linearity Noise and offset Supply rejection

9. When we go for two stage op-amp instead of one stage?

The gain and the output swing provided by some cascode op amps are not

adequate.

10. What is the objective of one stage op amp?

The objective is to maximize the output impedance so as to attain a high

voltage gain.

11. What is the idea behind the gain boosting?

To further increase the output impedance without adding more cascode

devices.

12. Define slewing.

Op amps used in feedback circuits exhibit a large signal behaviour called as slewing. Intensive property of linear system vanishes during slewing.

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13. Define power supply rejection.

The ratio of the change in supply voltage in the op amp to the equivalent output voltage it produces. It is expressed in decibels.

14. What is meant by buffer amplifier?

A buffer amplifier is one that provides electrical impedance transformation

from one circuit to another. Two main types of buffer exist: the voltage

buffer and the current buffer.

15. What is output voltage swing of an op amp?

Output voltage swing is defined as the maximum positive or negative

peak output voltage that can be obtained without wave form clipping.

16. Draw the gain roll-off with frequency.

17. What’s the difference between voltage-feedback And current

Feedback Op Amps?

Operational amplifiers (op amps) are analog circuits that amplify voltage. They may be constructed so their output voltage is based on the voltage difference across their differential inputs (voltage-feedback amplifiers, or VFAs) or on the current flowing between those inputs (current-feedback amplifiers, or CFAs). There are advantages and disadvantages to both types of op amps. They are used to condition and amplify analog signals in many applications.

18. Draw the diagram of voltage to voltage feedback.

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19. Draw the diagram of current to voltage feedback.

20.Draw the diagram of voltage to current feedback.

21. Draw the diagram of current to current feedback.

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Unit – IV STABILITY AND FREQUENCY COMPENSATION

1. Define Barkhausen criteria.

If βH(jω1) = -1, then the circuit may oscillate at frequency ω1. The condition

can be expressed as,

| βH(jω1) | = 1

βH(jω1) = -1800ے

Which are called Barkhausen criteria.

2. Define phase margin.

It is the difference between the phase measured in degrees and 1800 for

amplifier’s output signal as a function of frequency.

3. Define root locus analysis.

It is a graphical method for examining how the roots of a system change

with variation of certain parameter commonly gain within a feedback system.

4. Define frequency compensation. It is a technique used in amplifiers employing negative feedback. To avoid

unintentional creation of positive feedback and to control overshoot and ringing

in the amplifier’s step response. To improve the bandwidth of single pole

systems.

5. What is dominant pole? It is a pair of complex conjugate pole which decides transient response of

system.

6. What are the different methods of frequency compensation? Miller compensation

Feed forward

Self compensating

7. What is pole splitting? Pole splitting is a phenomenon used in an electronic amplifier. When a

capacitor is introduced between the input and sides of the amplifier and it

moves the output pole away from the origin. This effect is called pole splitting.

8. What is miller compensation?

It accounts for the increase in the equivalent input capacitance of an inverting

voltage amplifier due to amplification of the effect of capacitance between the

input and output. The increased input capacitance is given by,

CM = CC (1+Av2)

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9. Define slew rate.

It is defined as the rate of change of output voltage per unit of time.

SR = Max ( |dvout/dt| )

10. What are poles and zeros? Transfer function ,

H(S) = N(S) / D(S)

Where, N(S) & D(S) are polynomials

Zeros are the roots of N(S) obtained by setting N(S) = 0 and solving for S.

Poles are the roots of D(S) obtained by setting D(S) = 0 and solving for S.

11. What is non-dominant pole?

When the sum of loop poles is smaller than the sum of required system

poles, the loop poles cannot be placed in the desired position at least one loop

pole is too far away from the origin. Such a pole is called non- dominant pole.

12. What is the need for compensation? It arises because |βH| does not drop to unity before ےβH reaches -1800.

Then stability can be achieved by

i) Minimizing the overall phase shift, thus pushing phase crosses out. ii) Dropping the gain, thus pushing the gain crossover in.

13. Write the Poles for common gate.

14. Draw the Simplified Circuit In Positive Slewing (Two-Stage Op-

Amp).

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15. Draw the Simplified Circuit in negative Slewing (Two-Stage Op-

Amp).

16. Draw the Compensation technique using common gate.

17. Draw the common gate positive slewing.

18. Draw the Common gate negative slewing.

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19. Draw the Simplified circuit for the source follower.

20. Write the Poles equation for common drain.

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UNIT 5 BIASING CIRCUITS

1. Draw the basic current mirror circuit.

2. Draw the cascade current mirror circuit .

3. Write the voltage gain equation .

4. Write the over all voltage gain equation of the small signal analysis .

5. Write the CMRR equation.

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6. What are the three required temperature dependence forms? Proportion to absolute temperature. Constant Gm behaviour. Temperature independence.

7. Draw the generation of a PTAT current.

8. Write the bias current equation.

9. What are the problems occurred by addition of starts-up device?

The problem of start-up generally requires careful analysis and simulation. The

supply voltage must be ramped from zero in a DC sweep simulation as well as

in a transient

Simulation and the behaviour of the circuit examined for each supply voltage.

10. Write temperature coefficient of the base emitter voltage ?

11 .Define positive TC voltage

If two bipolar transistor operate at unequal current densities , then the

difference between their base-emitter voltages is directly proportional to the

absolute temperature.

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12. Write the equation for the negative feedback factor.

13. Write the equation for the positive feedback factor.

14. Write the equation for the bandgap reference.

15. Draw the graph of curvature in temperature dependence of a bandgap

volatage.

16. Draw the graph for the variation of the zero TC temperature for

difference samples.