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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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