Interview Questions : Analog Circuit Designing

Hi Friends

Welcome to the world of analog designing, I am Ravi, I did my M.tech. from HBTI Kanpur & presently I am working in a MNC as an Analog Circuit Designer.
As u all know that analog designing is one of the most challenging as well as highly paid jobs in VLSI industries, so getting Job as an analog designer is not so easy, below I have some collection of Analog Questions which may help you during your interview of analog designing.

For Analog designing interview, you should know

Analog Designing
the basics theorems of network systems
Analysis of Second order systems (Peak overshoot, Settling time, damping factor etc)
Stability analysis by the help of nyquist & bode plot
Analysis of Z,Y,H & G Parameters in two port network
Concepts of poles & zeros
Miller theorem (very important)
Diode & BJT characteristics
MOS transfer characteristics, Small & large signal analysis.
Basic CMOS inverter output vs input characteristics , region of operation & small signal analysis  
Small signal analysis of  various amplifiers ( common source, common Gate, Common Drain & cascode )
differential Amplifiers ( small signal analysis & input vs output plot )
current mirror
Bandgap Reference, Regulator & V2I
OPAMP, stability analysis of OPAMP, Miller compensation & Method to cancel positive zero
Types of Noise
 Oscillator & Phase lock loop
 ADC & DAC ( at least theoretical analysis )

Analog Backend
Analog Layouts techniques (Match transistors patterns, Match routing, shielding nets , resistors & capacitors layouts )
latchup, electro migration, Hot electrons, Antenna Effects, OPC, Phase shift mask & CMP etc
short channel effects in mosfets
Worked on various simulators, layout editors & layout verification tools
Worked on DRC,LVS,DFM,PERC,LFD & parasitic extraction flow
Knowledge of scripting language like TCL, shell & awk commands

Analog Verification
Knowledge of Verilog-A, Verilog AMS, Verilog
Worked on Analog Simulator & AMS Simulator
    Analog Simulator like : eldo,hspice,spectre etc
    Fast Analog Simulator :- Ultrasim, ADiT etc
    Mixed signal Simulator :- Cadence AMS irun env. etc

Analog Validation (if u know these then it will give u added advantage)
knowledge of instruments like Data Generators, High Bandwidth Scope & probes, Logic analyzer, time domain reflectometry, thermostream etc

Good books on Analog CMOS

Title: CMOS Analog Circuit Design-Phillip
Author: E. Allen, Douglas R. Holberg, Allen

Title: Analysis and Design of Analog Integrated Circuits
Author: Paul R. Gray, Paul J. Hurst, Stephen H. Lewis, Robert G. Meyer

Title: Design of analog CMOS Integrated Circuits
Author: Behzad Razavi

Analog Interview Questions
  1. State whether True or False

     a)     Electro migration depends on current.
b)     In LOCOS selective oxide growth is achieved using Silicon dioxide.
CVD process does not consume underlying silicon

         2.       To remove antenna effect which method is used
                   (i) Metal Splitting    (ii) Putting Antenna diode    (iii) Metal Slotting    (iv) Metal Over   Etching

                        (a)        (i) and (iii) are true
                        (b)        (i) and (ii) are true
                        (c)        (i) (ii) and (iii) are true
                        (d)        (ii) and (iv) are true

       3.          In an Inverter circuit if the following condition lies for input voltage

                      Vin = Vdd/2                            then

                        (a) n-mos will be in cut off and p-mos will be in linear region
                        (b) n-mos will be in linear and p-mos will be in cut off region
                        (c) n-mos and p-mos both will be in cut off region
                        (d) None of these

4)                Calculate Rz for both circuits ? ( NMOS are connected  in diagrams shown below )       


           Figure 1


5)                If Vg1 is fixed to  2.5V  and Vg2 is sweep from 0 to 5V, Draw Vout waveform  ( assume VDD = 5V )


Figure 2 


6)    Assume threshold voltage of PMOS is Vt   & NMOS is Vt   , a input pulse from VSS to VDD is given to circuit shown           

      below, Draw the output waveform  

   Figure 3 


7)      Which of these two amplifiers (in fig 4)have higher Gain? ( assume W/L of all transistors are same ), If Bias Current through M5 increase, what happens to gain ?

8)      Which of these two amplifiers (in fig 4)have higher bandwidth? ( assume W/L of all transistors are same ), If Bias Current through M5 increase, what happens to Bandwidth ?

(Figure 4)


9)      Tell me the advantages of amplifier shown in figure 5 over those shown in figure 4 ? 


                                                                                (Figure 5)


10)  What is a miller compensation technique? 

11)  Draw an OPAMP & tell me various poles & zeros associated with the circuit you draw ? How you will stabilize your system?  

12)  Which OPAMP is easy to design, OPAMP with capacitive load or OPAMP with resistive load ?  

13)    What is DIBL effect in MOSFET? Describe it with energy band diagram? 

14)    What are main advantages of making CMOS circuits working in sub threshold regions? 

15)   Describe Electro migration effect? & ways to reduce Electro migration during layouts? 

16)    What is CMP dishing?  How metal slotting & dummy metal help in reducing CMP dishing ? 

17)    Describe OPC techniques & phase shift mask? 

18)   What is Latch up? Tell me at least 5 ways how we can reduce probability of a latchup in ur circuit ? 

19)  Draw the layout of M1 & M2 transistor in figure 5 (hint : - take care of Matching pattern , Match routing & guard ring etc ) .

20 ) how you can match you resistor & capacitor layouts ? 

21 ) what are advantages of Common centroid & interdigitized patterns

22) Calculate Vout/Vin ?(in fig 6)

(Figure 6)


23) Calculate Rin(input Resistance) ?(in Fig 7)

(Figure 7)

24) Calculate Vout ?

(Figure 8)



Analog Interview Questions Download-I
 Analog Questions 2 (Dowload  pdf)

Analog Interview Questions Download-II
Analog Questions 2 (Dowload  pdf)


Good books on Analog Layout


Title : Excellent book for engineering students
Author : Alan Hastings

Good books on Electronics Circuits

Title: Microelectronic Circuits
Author: Adel S. Sedra, Kenneth C. Smith

Title: Integrated electronics

Title : Electronic Devices and Circuit Theory
Author : Robert L. Boylestad, Louis Nashelsky

Important & useful links

Lecture Series

Analog Notes

Notes on Analog and Mixed Signal VLSI Circuit Design
Dr. Navakanta Bhat
Professor, ECE Department
Indian Institute of Science, Bangalore-56001

CMOS Analog Quick reference Guide






Hi Friends you can send me analog question asked during your interview, I will include your mails in this webpage.
My Email is analog.ravi@gmail.com


2006 Learn Analog