Voltage divider

Voltage divider is just two resistor connected is series, but powerful tool for calculating electrical potential of some nodes. Instead of solving sys tem of equations, all we need to do in order to calculate output voltage of an voltage divider is to find quotient of resistor value and sum of two re sistors that makes voltage divider, and then to find product of this quotie nt and input voltage.

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Reply to
Patrick Chung
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Lately I use Spice to work out resistor networks past two resistors or so. Saves a lot of algebra, especially when I'm trying to use values in stock.

One trick, when actually calculating, is to start with 1 ohm or whatever is easiest to do the math on, and normalize once all the values are worked out.

Reply to
John Larkin

Seems like whipping up a little Python script where you plug in the output fractions you need from each tap and it spits out a list of what the resistors should be from whatever series shouldn't be too hard...

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Reply to
bitrex

(1) Patrick Chung is a troll with a website where he envisions himself an expert on electronics. Killfile him.

(2) Spice _is_ actually more convenient than having to conjure up a script. I presently have a "schematic" that takes information from an OpAmp datasheet and generates 12 parameters (numeric) allowing the OpAmp's behavior to be described with _just_two_ behavioral equations:

DC Gain, Gain Bandwidth, Slew+, Slew- and integrator (compensation) hang-up.

I'm pondering a similar approach to output stages.

Already complete are excess phase, secondary pole and noise modules.

When complete, modeling will be as simple as pasting modules together. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

I wrote a little Windows program that prowls the resistors that we have in stock, to try to hit a given ratio and Thevenin impedance. It's in PowerBasic.

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Output looks something like...

RUGRAT Resistor ratio report 10-16-2015 09:05:47

Target ratio 5.640000 Accuracy limit 0.200 per cent Thevenin 500.000 to 2,000.000 Types 0603

Ratio 5.643478 Error 0.062 pct Thevenin 976.898

131-5781 RES 0603 6.49K 1% PANASONIC ERJ-3EKF6491V 0.00 83 131-5061 RES 0603 1.15K 1% MOUSER 302-1.15K-RC 0.00 339

Ratio 5.643478 Error 0.062 pct Thevenin 976.898

131-5781 RES 0603 6.49K 1% PANASONIC ERJ-3EKF6491V 0.00 83 131-5062 RES 0603 1.15K 0.5% SUSUMU RR0816P-1151-D-07 0.01 334

Ratio 5.629032 Error -0.194 pct Thevenin 1,052.944

131-5811 RES 0603 6.98K 1% VISHAY DALE CRCW06036K98FKEA 0.01 82 131-5092 RES 0603 1.24K 0.1% KOA RN731JTTD1241B25 0.14 213

Ratio 5.639098 Error -0.016 pct Thevenin 1,129.672

131-5840 RES 0603 7.5K 5% MOUSER 301-7.5K 0.01 95 131-5121 RES 0603 1.33K 1% MOUSER 660-RK73H1JLTD133 0.00 94

Ratio 5.639098 Error -0.016 pct Thevenin 1,129.672

131-5842 RES 0603 7.5K 0.1% 0.14 58 131-5121 RES 0603 1.33K 1% MOUSER 660-RK73H1JLTD133 0.00 94

Ratio 5.633333 Error -0.118 pct Thevenin 1,273.869

131-5891 RES 0603 8.45K 1% MOUSER 660-RK73H1JLTD845 0.02 58 131-5170 RES 0603 1/16W 1.5K 5% DIGIKEY P1.5KGCT-ND 0.02 81

Ratio 5.633333 Error -0.118 pct Thevenin 1,273.869

131-5891 RES 0603 8.45K 1% MOUSER 660-RK73H1JLTD845 0.02 58 131-5172 RES 0603 1.5K 0.05% 0.44 37

Ratio 5.633333 Error -0.118 pct Thevenin 1,273.869

131-5892 RES 0603 25PPM 8.45K 0.1% VISHAY TNPW06038K45BEEA 0.37 23 131-5170 RES 0603 1/16W 1.5K 5% DIGIKEY P1.5KGCT-ND 0.02 81

Ratio 5.633333 Error -0.118 pct Thevenin 1,273.869

131-5892 RES 0603 25PPM 8.45K 0.1% VISHAY TNPW06038K45BEEA 0.37 23 131-5172 RES 0603 1.5K 0.05% 0.44 37
Reply to
John Larkin

Spice? Python? Why bother with all that when the world is at your fingers in Excel or LibreOffice Calc as the case may be? I've done the optimal resistor ratio search a number of times using a simple table with resistor values on both axes and ratios calculated in the body. Scan the table along a diagonal to look for the ratios of interest. Works great for standard values. If you want to customize it you can use conditional formatting to highlight close values making it easier to find them quickly.

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Reply to
rickman

Is he?

He does post links to his site here occasionally. I think he's more welcome here than political or gun talk.

I figured he was a student documenting what he learnt as he went.

Reply to
Oltimer

He's just clickbaiting - trying to get eyeballs on his shitty site so he can make ad revenue. It's likely that most of the 'content' isn't even his but pulled from somewhere without permission.

Fuck him

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Reply to
bitrex

What are you doing talking sense?

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Rick
Reply to
rickman

Your secret's out now

NT

Reply to
tabbypurr

I have seen no evidence to suggest otherwise

which s worse, trolls or spam, that's a tough call.

If so, he's learning an a funny order.

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Reply to
Jasen Betts

I don't see this as a big deal. He does not argue with others. He just posts his stuff and goes away. You don't like it? It is easier to ignore than the persistent junk posted by AW. Which do you prefer?

Reply to
John S

Do you click on his site? If you understand his motives and do so, who is to blame?

Reply to
John S

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