Design engineer Interview Questions


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Software Design Engineer was asked...19 March 2009

Given a string find the first non-repeated character.

12 Answers

@Rajiv : Your solution is completely wrong. It will fail for input of "aaa" Reason: on first check, you insert "a". On next check you remove it. On next check you again insert it and return that as your answer, even though it was repeated thrice. Less

program to find first non repeating character in a string c# - three ways

My python implementation: def firstNonRepeatingCharacter(inputString): hashmap = {} for x in inputString: if (x in hashmap): hashmap[x] = hashmap[x] + 1 else: hashmap[x] = 1 for x in inputString: if (hashmap[x] > 1): continue else: return x return "No nonrepeating character found" Less

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Dolphin Technology

Basic MOSFET, CMOS questions were asked.

11 Answers

Hey, you should feel glad that you weren't accepted by them. This company is very cheap and doesn't treat its employees well. Less

I guess...but it is not the right way to interview candidates don't you think?

That's really sad. They should rather go with Skype or any other means to interview. Now,. I have got an on-site call for Digital circuit design and I am giving it a serious thought 🤔 Less

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need to join tomorrow are you ready?

11 Answers


Yes sir

Yes I am ready to join

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There is a refrigerator in a perfectly insulated room. The door is then opened. Is it an open or closed system? After a long time has passed, has the temperature in the room increased or decreased?

8 Answers

It is a closed system as electricity is adding energy into the room. After a long time passes, the temperature increases as there's energy going in, but not leaving. Less

Since there is energy going into the room, it is open system without mass transfer. The room temperature will increase. Less

closed system; draw the p-h diagram; condenser power = evaporator power + compressor power; as long as compressor works; there is always more heat rejected through condenser than the cooling power provided by evap; it has nothing to do with isentropic efficiency (even compressor works at 100% efficiency and no loss through the system) Thus, locally air temp in front of the door decreases; overall average temp in the closed system keep increasing; Less

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Create a 8 input AND gate using 3 4:1 muxes

8 Answers

Without an enable bit on at least one of the mux's the maximum inputs would be 7. Less

I don't see it being possible with three standard 4-1 muxes... Using 4, this question is straight forward... The two selects of each mux are your 8 inputs... tie out put of each mux to the (11) case input to the mux. Less

We need 3 4:1 MUX and a And gate. Are we allowed to use 'and' gate?

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Show me the back of an iPhone and asked me how it might have been manufactured.

8 Answers

Automated CNC milling

A cast polymere

Still don’t get it

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design a full adder with 2-1 mux

6 Answers

full adder can be got by 2 half adders and one OR gate; one half adder can be got by XOR, AND. Therefore, we need only OR, AND, XOR. All these three gates can be got by using MUX.? Less

sum = a xor b xor cin carry = (a xor b) cin + ab You can easiy make XOR, OR AND, NOT using 2:1 mux. So 8 mux ?!? Less

if Mux(I1,I2,S) is a 2x1 mux module, then Sum = Mux( (Mux(C,C',B), Mux(C',C,B), A) which requires 3 2x1 mux. Carry = Mux( (Mux(0,C,B), Mux(C,1,B), A) which requires 3 2x1 mux. Less

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Intel Corporation

CMOS Inverter , how to reduce the drive strength of Minimum size inverter

6 Answers

"more the Ids, the lesser the drive strength is" This is exactly opposite of the actual fact...! Less

Use body effect, reverse biasing, this will reduce the drain current. another way can be change the gate input, according to the I-V characteristic Less

the first answer is definitely wrong, to decrease the driving capacity, please size down the ratio! Less

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You have 5kg of Aluminum and 5kg of Steel. You can make whatever cross section beam you want with these materials. If you have to make a cantilever beam 1m long with a load at the end. And you want to minimize the deflection. What material would you use?

6 Answers

Aluminum. While the previous post on Sep 5th is correct in stating that P, L are the same, since you are given a mass of both metals, you need to find you allowable "volume" of material, which you can estimate using 2700kg/m3 for Al and 7800kg/m3 for steel. MoI is given by (1/12) b h^3 if you assume b (base) is the same for both materials, you'll find that h for aluminum is greater than h of steel, and since h is cubed, it actually makes a big difference. In my test case, E of steel ~3x greater (200 GPa vs 70 GPa), but the moment of inertia of the Aluminum was ~3.75x than steel, meaning that deflection of aluminum would be less than steel! Less


Why is it being assumed that the base be the same for both materials. Since the question allows to choose whatever cross section we are allowed, can we not just assume that we'll come up with a MoI that's comparable? Or we simply switch the b and h values for both materials. Given these assumptions, one could argue that the deflection is a function of E and thus, higher in aluminum and lower in steel. Less

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If you and a large brick are in a boat floating in a pool, will the water level rise or fall when the brick is tossed into the water? What if the brick is a large piece of Styrofoam and thrown into the water?

6 Answers

Your answer indicated the necessity of this question.

The water level will decrease ( if the brick has a density greater than water, which of course a conventional brick does). When in the boat, the brick will displace a mass of water equal to it's own. So if it has a mass of 1kg it will displace 1kg of water. When thrown overboard it will now displace an amount of water equal to it's volume. As it sinks, it's density must be grater than water and therefore it's 1kg mass will take up a smaller volume than 1kg of water. Therefore the water level will decrease. As a styrofoam brick has a lower density than water it will not sink when thrown overboard. When floating it will displace a mass of water equal to that of the brick and therefore the water level will remain the unchanged. Less

A powerful tool in looking at questions like these intuitively rather than by the raw physics is to go to the extreme. Say the brick were of normal brick size but were made of some ultra-dense dense that it would push an aircraft carrier down in the water to the brink of sinking. This would obviously cause the carrier to displace many thousands of gallons more water than it had been displacing before the brick was added. When the brick is thrown overboard, the carrier would come shooting up out of the water, now not displacing those additional thousands of gallons of water The volume of water displaced by the brick once it's in the water is comparatively insignificant. So clearly the water level will fall. Less

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