## aaban 2 years ago The resistances of commercially-available discrete resistors are restricted to particular sets. For example, the available values of resistors with 10% tolerance are selections from the E12 set multiplied by a power of ten from 100 through 105. The E12 set is: E12={10,12,15,18,22,27,33,39,47,56,68,82} Thus, you can buy 10% resistors with a nominal resistance of 330Ω or 33kΩ, but not 350Ω. Furthermore, the "tolerance" means that if you buy a 10% 390Ω resistor you can be sure that its resistance is between 351Ω and 429Ω. In this problem we need to choose 10% resistors to make a current divi

1. abdullatif92211

whats then problem in this problem??

2. aaban

need help how to start solving it? even an hint will be appreciated

3. abdullatif92211

A little help: H2P1 Hints: The goal of this Problem is that you can learn how to choose normalized values based on some data :). In the statement, they give you the following circuit and they request you to find the values of RS and RL, and the maximun and minimun current that you will have in the load (iLmax and iLmin): They give you as data Iin (current of input) and IL (current of load) - in my case I have Iin=100uA and IL=40uA, you can have another random value :p An additional requirement is that the Thevenin resistance as seen from the load terminals is between 60kΩ and 80kΩ - this are my specific range values given in my statement, you can have another random ones-. So, they are telling you that your thevenin resistance (take a look at the green box), is between 60kOhms and 80k0hms.

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Hint 1: How can you calculate a thevenin resistance? Take a look at page 157 of the Textbook read here . What do you have to do with your current or your voltage sources in order to get your thevenin resistance? What happens ifyou don`t have your current source? What value of resistance do you have? :) Take a look at the examples of the page 171 of the Textbook read here - example 3.28 :p Now is your turn. Try to find the thevenin resistance of the green box. You can call it as Rth.

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Hint 2: A clue, try to adopt a value of Rth betwee the given range :p. You will get an equation in terms of your resistances :).

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Hint 3: Can you relate Iin and IL with your resistances of the circuit? Take a look at this page, page 80 of the Textbook read here . Does current dividers rings you a bell? :p So can you relate RS, RL and Iin and IL? Yes! Do you have your Iin? Yes. Do you have your IL? Yes. So, can you find the ratio IL/Iin? Yes!

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Hint 4: If you have two equations with two incognits can you find the system? :) Yes! So, now it is your turn Try to find your Rs and RL. Remember that you have to choose standard values.

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What about iLmax and iLmin? Once you have calculated your standard RS and RL, you will find that RS will have maximun value and a minimun value, also RL. That is because the tolerance of the 10% -remember that RL and RS are the standard values that you have chosen:

9. aaban

thanks you very much, i'll start solving it now

10. abdullatif92211

So, try to think, when you will have your maximun current in your load and when you will have your minimun current in your load - Remember that if you buy a resistor with some tolerance you can have a range of possible value , eg., the "tolerance" means that if you buy a 10% 390Ω resistor you can be sure that its resistance is between 351Ω and 429Ω.: Try it . Last Hint. Hint 5: Your previous current divider with your new data it will be a good help ;)