analysis and design of analog ic
DESCRIPTION
ADAIC TWO MARKS QUESTIONS AND ANSWERSTRANSCRIPT
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
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.