Bunch of questions I need answers to

[blackdragon12]

Hey guys so Ive been studying upon these topics recently and these are some questions that I was presented with from discussing these topics with other electronic engineers.. any help is appreciated

1. How do you lay a PCB board out?

2. Define Gain margin and Phase Margin

3. What is sampling frequency corresponding to 10kHz signal?

4. What is CMOS capacitance?

5. Describe what a short circuit is and how to solve it?

6. How would you amplify 100mV to 1V?

7. Why does a ring oscillator oscillate?

8. Design a 128:1 MUX from 4:1 MUX. How many MUX and selection lines are needed?

9. How do you test a regulator?

10. Can you draw an inverting op-amp?

11. Build a 2NAND out of MUXs

12. Convert a 2’s complement 16-bit string to compute its absolute value

 

[godfreyl]

Nice questions. I hope you don't expect quick answers to all of them. Where are they from - a homework assignment, a job application, or what?

 

[snishanth512]

Answer to 1st question:
Using Eagle software or other PCB designing software. Before you design make sure that you know all measurement (holes diameter using screw gauge).

Answer to 3nd question:
Sampling frequency should be decided based on nyquist rate. (Note: refer communication systems by proakis)

Answer to 4th question:
Refer VLSI Technology by SZE (2nd Ed.)

 

[blackdragon12]

Nice questions. I hope you don't expect quick answers to all of them. Where are they from - a homework assignment, a job application, or what?

No no, not a homework assignment. The topics are too broad to be honest to be covered in a single course.

But this is just to help me revise the basics and have a reference to go to when I need a refresher, should help others too!

 

[snishanth512]

Answer to 5th question:
(i) Short circuit is a part of the circuit where the current becomes infinite (if it is a battery powered ckt then the battery wil drain soon).
(ii) Can be found by checking all the loops of the circuit. If you are not confident about the circuit design to try to implement in simulation software.

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Answer to 6th question:
Use an non-inverting amplifier with a grain of 10. (Note: refer microelectonics circuits by sedra smith or opamps by sergio franco)

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Answer to 8th question:
you need 43 (4x1) muxes to implement a (128x1) mux.
or
You need 42 (4x1) muxes and a (2x1) mux to implement a (128x1) mux.

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Answer to 12th question:
Take 1's complement and add one.
or
XOR the 16-bit value with 1111 1111 1111 1111.
And add with 1.

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Answer to 10th question:


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Answer to 11th question:

 

[blackdragon12]

Answer to 5th question:
(i) Short circuit is a part of the circuit where the current becomes infinite (if it is a battery powered ckt then the battery wil drain soon).
(ii) Can be found by checking all the loops of the circuit. If you are not confident about the circuit design to try to implement in simulation software.

- - - Updated - - -

Answer to 6th question:
Use an non-inverting amplifier with a grain of 10. (Note: refer microelectonics circuits by sedra smith or opamps by sergio franco)

- - - Updated - - -

Answer to 8th question:
you need 43 (4x1) muxes to implement a (128x1) mux.
or
You need 42 (4x1) muxes and a (2x1) mux to implement a (128x1) mux.

- - - Updated - - -

Answer to 12th question:
Take 1's complement and add one.
or
XOR the 16-bit value with 1111 1111 1111 1111.
And add with 1.

- - - Updated - - -

Answer to 10th question:
View attachment 91272

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Answer to 11th question:
View attachment 91273

Wow thanks! I have updated the main post and bolded the remaining questions

 

[godfreyl]

I'll take a shot at #2

This refers to the loop gain of a negative feedback system.

• Phase margin = the phase at the frequency where gain = 0dB
• Gain margin = (1 / gain) at the frequency where phase = 0
  Expressed in decibels, that's (0 - gain in dB)

In the example below, Gain margin = 50 degrees and Gain margin = 5dB.

NB: We're talking about the magnitude and phase of the loop gain, not the open loop gain or the closed loop gain.

 

[BradtheRad]

Re question #9:

You test a regulator either by changing the supply voltage, or by changing the load resistance.

How it responds depends on whether it is a voltage regulator or current regulator.