Difference between revisions of "Passives"
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[[Image:Cap_basic_equ.png|c=q/v]] | [[Image:Cap_basic_equ.png|c=q/v]] | ||
| − | + | Where: | |
| − | C = capacitance ( units: farad = volts /coulomb ) | + | |
| − | V = voltage ( unit: volts ) | + | *C = capacitance ( units: farad = volts /coulomb ) |
| − | Q = charge in the capacitor ( unit: coulomb ) | + | *V = voltage ( unit: volts ) |
| + | *Q = charge in the capacitor ( unit: coulomb ) | ||
A simple application of the formula above occurs when a constant or near constant current flow into a capacitor: then the voltage across it increases at a constant rate, the graph of the voltage against time will be a line rising ( or falling for a negative current ) from the left to the right. If the current is constant the line is straight. | A simple application of the formula above occurs when a constant or near constant current flow into a capacitor: then the voltage across it increases at a constant rate, the graph of the voltage against time will be a line rising ( or falling for a negative current ) from the left to the right. If the current is constant the line is straight. | ||
| − | Uses | + | |
| − | ac coupling – blocking -- isolation | + | Uses: |
| − | timing | + | |
| − | Time for a capacitor to charge or discharge is very roughly RC where R is the resistor in series with the capacitor. | + | * ac coupling –- blocking -- isolation |
| − | Filter ( often power supply filter ) | + | * timing |
| − | decoupling | + | * Time for a capacitor to charge or discharge is very roughly RC where R is the resistor in series with the capacitor. |
| − | tuned circuits | + | * Filter ( often power supply filter ) |
| + | * decoupling | ||
| + | * tuned circuits | ||
There are many diferent technologies for manufacturing capacitor each with its own advantages and disadvantages. | There are many diferent technologies for manufacturing capacitor each with its own advantages and disadvantages. | ||
| − | Some capacitors manufactured between 1999 until today are made with bad electrolyte. Avoid these, see [[Capacitor plague]] for more info. | + | <BR>Some capacitors manufactured between 1999 until today are made with bad electrolyte. Avoid these, see [[Capacitor plague]] for more info. |
| + | |||
| + | External Links | ||
| + | |||
| + | # [http://en.wikipedia.org/wiki/Capacitor Capacitor From Wikipedia, the free encyclopedia] | ||
| + | # [http://en.wikipedia.org/wiki/RC_circuit RC circuit From Wikipedia, the free encyclopedia] | ||
| + | # [http://www.northcountryradio.com/PDFs/column008.pdf RC Timers and Timing Circuits] | ||
| + | # [http://en.wikipedia.org/wiki/Decoupling_capacitor Decoupling capacitor From Wikipedia, the free encyclopedia] | ||
| + | |||
=== Electrolytic === | === Electrolytic === | ||
==== Aluminum ==== | ==== Aluminum ==== | ||
Revision as of 12:51, 13 January 2008
This article is a stub. You can help Open Circuits by expanding it.Contents
Capacitors
Basics
You can think of a capacitor as sort of a rechargeable battery, connect it to a voltage and a current will flow into it charging it up, later it will have a voltage of its own that can push the current back out. The key equation for a capacitor is:
Where:
- C = capacitance ( units: farad = volts /coulomb )
- V = voltage ( unit: volts )
- Q = charge in the capacitor ( unit: coulomb )
A simple application of the formula above occurs when a constant or near constant current flow into a capacitor: then the voltage across it increases at a constant rate, the graph of the voltage against time will be a line rising ( or falling for a negative current ) from the left to the right. If the current is constant the line is straight.
Uses:
- ac coupling –- blocking -- isolation
- timing
- Time for a capacitor to charge or discharge is very roughly RC where R is the resistor in series with the capacitor.
- Filter ( often power supply filter )
- decoupling
- tuned circuits
There are many diferent technologies for manufacturing capacitor each with its own advantages and disadvantages.
Some capacitors manufactured between 1999 until today are made with bad electrolyte. Avoid these, see Capacitor plague for more info.
External Links
- Capacitor From Wikipedia, the free encyclopedia
- RC circuit From Wikipedia, the free encyclopedia
- RC Timers and Timing Circuits
- Decoupling capacitor From Wikipedia, the free encyclopedia
Electrolytic
Aluminum
Tantalum
Ceramic
Film
Polyester (Mylar)
Polystyrene
Polycarbonate
Polypropylene
Teflon
Exotics
Mica
Glass
Oil
Vacuum
Inductors
"Ferrites? I don't know much about 'em, I only use ferrites in switching regulators." --National Semiconductor's Bob Pease
Can be replaced in many circumstances with an impedance inverter using only an opamp, a capacitor, and a few resistors.
Resistors
List of standard 1% resistors. If you want 1% resistors, you must pick from this list or you will pay a fortune for the resistor, assuming you can ever get it. Interpret these numbers as the "mantissa" of the value. You can multiply the value by anything from 0.01 to about 100,000.
100 102 105 107 110 113 115 118 121 124 127 130 133 137 140 143 147 150 154 158 162 165 169 174 178 182 187 191 196 200 205 210 215 221 226 232 237 243 249 255 261 267 274 280 287 294 301 309 316 324 332 340 348 357 365 374 383 392 402 412 422 432 442 453 464 475 487 499 511 523 536 549 562 576 590 604 619 634 649 665 681 698 715 732 750 768 787 806 825 845 866 887 909 931 953 976
