# basic analog integrated circuits test

Thread Starter

#### Ondroid

Joined Apr 15, 2014
3
Hello,
i would like to ask for your help with these two problems :

I've got the answers i'm just not quite sure how to get to those answers.I've got the basic knowledge in analog electronics i just have a difficult time putting it all together.I would like to know if there are any things in particular to watch out for when dealing with these kinds of problems or better yet if there's any kind of a general algorithm i should follow when solving them.
I guess the bottom line is how do i go about solving this ?

Thank you for your help.

Ondroid.

#### Alec_t

Joined Sep 17, 2013
11,651
Whenever you have a npn transistor in circuit, remember that it begins to turn on when the base-emitter voltage is > about 0.6V.
With an inductor, remember that it resists change in current through it, so current will ramp up or down.

#### WBahn

Joined Mar 31, 2012
26,156
You SAY you have the answers, but don't give them. How do WE know you actually have the answers versus just saying that to try to trick us into providing them for you? People do that here, so you are going to get painted with that brush unless you do differently.

You need to show your best effort at working the problems. Which figures do you know can't be the answer, and why? What characteristics must the correct figure have, and why?

Thread Starter

#### Ondroid

Joined Apr 15, 2014
3
Well, it's C and B (from left to right), but i wasn't asking about that ... i'm just interested in any kind of pointers or "good habits" if you will, when solving these types of problems.Maybe if there's a step by step approach to it, or if there's something i should always start with.. Anything really.

#### WBahn

Joined Mar 31, 2012
26,156
So, let me reiterate, which answers can't be correct, and why? What characteristics must the correct answer have, and why?

Also, consider the behavior at the extreme ends of the range.

Consider things like whether the characteristic has to be monotonic or not.

Often time those qualitative measures are sufficient to narrow the choice to a single option. That's the case with the first one.

Consider the second problem. You have two solutions in which the current is always positive and two in which it is both positive and negative. Can you determine whether the actual current can be both positive and negative? Can you determine if it must always be positive? Or if it must be both positive and negative? That might eliminate half the possibilities right there.

If that isn't enough, you can always simply analyze the circuit (if you have enough time).

Thread Starter

#### Ondroid

Joined Apr 15, 2014
3
Thanks a lot ! This is exactly what i was looking for.This quote popped up in my head instantly :"Knowledge is having the right answer, Intelligence is asking the right question"

Well i gues i have but one more question.
Is there any book with more examples like these ? I should really think about this stuff more, but i don't have any other examples to practice on.
Any ideas ?

And again, thank you !

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