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Few questions (multiple-choice)

Joao Fonseca

Oct 10, 2017
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Hello all,

I have some doubts in the following multiple-choice quesitons. Can you please help me to get the correct answer?
Images attached.

Maybe I'll have more in the following days but for now these are my doubts.


Thank you!
 

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AnalogKid

Jun 10, 2015
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Tell us your answers and we'll tell you if they are correct. Don't just guess; explain your thinking.

ak
 

Joao Fonseca

Oct 10, 2017
3
Joined
Oct 10, 2017
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Hi there!

For the transformer question I would choose a) because if there is the need to increase impedance than the secondary has to have more turns than the primary. Zp/Zs=(Np/Ns)^2

For the RC active filter question, I'd choose b) due to the fact that there is no perfect capacitor and some inductance will be present, which may have a significative effect at higher frequencies.

For the picture, I'd pick the a) just because all of the other answers are not correct for my thinking. Even for a) I have still doubts because if it is a DC-DC regulator for me the C1 is there just to filter the input DC signal which may contain some voltage fluctuations.
 

AnalogKid

Jun 10, 2015
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Transformer question - correct.

Voltage regulator question - I agree, none of the choices are great. It might be a mis-translation (to go with the misspelling).

There is no active filter question. For the active oscillator question - incorrect. Surface mount ceramic capacitors have self-resonant frequencies in the hundreds of MHz, way outside the bandwidth of the vast majority of opamps (interesting spelling).

ak
 

Joao Fonseca

Oct 10, 2017
3
Joined
Oct 10, 2017
Messages
3
First of all thanks for the quick reply!

For the active RC oscillator question... I'd pick c) as I understand that there is no ideal OpAmp so there is a limitaion on high frequency response of them. In the real world, there's a limit on the highest frequency (bandwidth) and fasted edge the opamp can process.

Am I right?
 
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