voltage divider resistors
- Thread starter 2n2222
- Start date
Vague...care to expand, or direct to a source so I may educate myself, obviously I'm no electrical engineer Thanks
jessenator
Well-known member
I like this series. Going through them myself, since I'm also not an engineer.
specifically about voltage dividers:
specifically about voltage dividers:
ICTRock
Well-known member
you're looking for a factor of 10 between the two resistors but there's no harm going with something you have in stock so if you have 1M and 100K then use those. I personally wouldn't choose 430K and 43K unless I was just looking to use up some resistors I had lying around because I never use them. they're just not a very common parts call.
Thanks, I will check it out.
Aleph Null
Well-known member
Higher resistance means more heat and thermal noise, but also higher impedance and lower current. Impedance will be roughly equal to the value of the two resistors in parallel.
No sane values are going to create enough heat to cause problems. Thermal noise is very likely to be overshadowed by the guitar's high noise floor. Current probably doesn't matter unless you plan to run it on batteries. High impedance and all the high frequencies that come with it may not be desirable if you are going to slam the output into a cooking amp or some other gain stage.
Basically, in most applications, the values probably aren't critical and can be picked based on what you have in stock.
No sane values are going to create enough heat to cause problems. Thermal noise is very likely to be overshadowed by the guitar's high noise floor. Current probably doesn't matter unless you plan to run it on batteries. High impedance and all the high frequencies that come with it may not be desirable if you are going to slam the output into a cooking amp or some other gain stage.
Basically, in most applications, the values probably aren't critical and can be picked based on what you have in stock.
falco_femoralis
Well-known member
Judgment calls like that are so hard to make starting out. It's such a backwards line of reasoning when the rest of EE is so difficult and complicated. You have to learn and understand complex ideas like impedance in an AC circuit to realize it doesn't matter anyway.
What gets me is the formula for impedance as a product of resistance and reactance is the pythagorean theorem. How did they make that one line up?
Aleph Null
Well-known member
Yeah, it's tough. You have to understand enough theory to know when you should actually do the math, and when you can just hand wave away the particulars and go with "probably good enough".
Fortunately, small signal (AC) design at low frequencies (the audible range) is pretty forgiving. The ham radio and microprocessor guys have it rough!
leadfoot
Active member
I still remember my first audio circuits class after spending the previous year having to do a ton of complicated math to have the professor literally just say "none of those resistors matter, so just drop them and then just simplify this complicated looking section to another resistor, now the gain of this op amp circuit is - r1/r2" and the entire class just cried.
jessenator
Well-known member
The course on that (from the series above) had some "use Thevenin only" example problems to solve, and I'd get halfway and realize I was using Ohm's law, so I'd have to restart.
