# resistor on top of each other....?

Discussion in 'General Electronics Chat' started by supermankid, Jul 21, 2014.

1. ### supermankid Thread Starter Member

May 26, 2013
36
1
Why is the resistor placed one on top of other...instead of using a separate voltage divider from the battery to compare the voltage....this resistor one on top of other just makes it look more complex and complex for calculation too....

Is there a special reason....a hidden trick in this circuit....I don't see the meaning of just complicating(besides saving...3 resistors)....

FYI: MAX8214

2. ### alfacliff Well-Known Member

Dec 13, 2013
2,449
428
it is a voltage devider. just has a lot of taps probably a adc (analog to digital converter) why would you want individual voltage devders? it sis a voltage devider ladder.

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3. ### Dodgydave AAC Fanatic!

Jun 22, 2012
5,139
767
Its a voltage ladder,each junction has a different voltage going lower from top to bottom,so that each comparator switches on as the battery voltage decreases,it uses less resistors than your conversion.

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4. ### crutschow Expert

Mar 14, 2008
13,474
3,361
By my count it save one resistor, but that's the reason it's preferred. Never use more components then you have too, especially just to simply a calculation.

To simplify the calculation of the string and avoid having to solve any simultaneous equations, you can start out by deciding what current you want through the network (it looks like about 7 microamps for the network shown). Then calculate the resistor values to give each of the desired trip-point voltages for 7 microamps through each resistor starting from the bottom and going to the top. That way you only have to solve one or two simple equations for each resistor value.

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5. ### MrChips Moderator

Oct 2, 2009
12,623
3,451
Because if you use n voltage dividers you will have severe non-linearity and possible non-monotonicity.

Using a ladder network reduces the non-linearity.

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6. ### NorthGuy Active Member

Jun 28, 2014
611
121
For n-tap ladder you need n+1 resistors. For n individual dividers you need 2n resistors. So you save 2n - (n+1) = n-1 resistors.

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7. ### wayneh Expert

Sep 9, 2010
12,371
3,224
Personally, I find the ladder simpler to understand, draw and build as well. To my eye, it's not more complicated, just the opposite. One glance and you see all the reference voltages at once. And it's not just numerical, the ladder arrangement actually gives a graphical cue about how the reference voltages are related.

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