1 / 41

Capacitors

Capacitors. BITX20 bidirectional SSB transceiver. A BITX20 single stage. A simplified single stage. A simplified single stage with capacitors. C4. C3. C2. C1. Illustrated applications of capacitors. Power supply decoupling : See capacitor C1 Signal decoupling : See capacitor C2

morrison
Download Presentation

Capacitors

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Capacitors

  2. BITX20 bidirectional SSB transceiver

  3. A BITX20 single stage

  4. A simplified single stage

  5. A simplified single stage with capacitors C4 C3 C2 C1

  6. Illustrated applications of capacitors • Power supply decoupling: See capacitor C1 • Signal decoupling: See capacitor C2 • Signal coupling: See capacitors C3 and C4

  7. Some other applicationsof capacitors • RC Filters: See later • Tuned circuits: In another talk (We need to discuss inductors first)

  8. Fields • Electric fields • Capacitors • Magnetic Fields • Inductors • Electromagnetic (EM) fields • Radio waves • Antennas • Cables

  9. Capacitors

  10. Discharge of a capacitor

  11. Graph of capacitor discharge from 10VR=1 Ohm, C=1 Farad (or R=1 M Ohm, C=1 uF)

  12. The same discharge from 27.18V e=2.718 10*2.718 10 10/2.718

  13. Exponential decay The RC decay time constant = R times C If R is in Ohms and C in farads the time is in seconds Every time constant the voltage decays by the ratio of 2.718 This keeps on happening (till its lost in the noise) This ratio 2.718is called “e”.

  14. Exponential decay It’s a smooth curve. We can work out the voltage at any moment. The voltage at any time t is: V = V0 / e(t/RC) V0 is the voltage at time zero. t/RC is the fractional number of decay time constants For e( ) you can use the ex key on your calculator

  15. Low pass RC filter

  16. RC = 1 secondVin = +/-10V square wave

  17. RC = 1 secondVin = +/-10V square wave

  18. RC = 1 secondVin = +/-10V square wave

  19. RC = 1 secondVin = +/-10V square wave

  20. RC = 1 secondVin = +/-10V square wave

  21. RC = 1 secondVin = +/-10V square wave

  22. RC = 1 secondVin = +/-10V square wave

  23. RC = 1 secondVin = +/-10V square wave

  24. RC = 1 secondVin = +/-10V sine wave

  25. RC = 1 secondVin = +/-10V sine wave

  26. RC = 1 secondVin = +/-10V sine wave

  27. RC = 1 secondVin = +/-10V sine wave

  28. RC = 1 secondVin = +/-10V sine wave

  29. RC = 1 secondVin = +/-10V sine wave

  30. RC = 1 secondVin = +/-10V sine wave

  31. What can we say about the phase? The voltage across a resistor is always in phase with the current through it The voltage across a capacitor lags the current through it by 90 degrees So in an RC series circuit the phases of the R and C voltages are 90 degrees different.

  32. Our low pass RC filter

  33. What can we say about the amplitude? The higher the frequency the more current is needed to charge and discharge a capacitor to the same voltage. (Ignoring phase) we could say it has less resistance the higher the frequency. This is what we call impedance. The impedance of a capacitor in Ohms is 1/(2Pi*f*C) Where f is the frequency in Hertz and C the capacitance in Farads. (2Pi*f is also known as the frequency in radians per second w)

  34. Vector diagram for the low pass Filter Leading Lagging So Vout lags (Vin-Vout) by 90 degrees. So we can calculate the filter output using Pythagoras As the frequency increases Vout moves round the circle from the top to the bottom on the right

  35. Vector diagram for the low pass Filter Leading Lagging This diagram shows the corner frequency of the filter. This is the 3dB down point and the phase lag is 45 degrees This happens when the impedance of R and C are the same. R = 1/(2Pi*f*C).

  36. Low pass gain against frequency 0.707

  37. Low pass phase against frequency -45

  38. High pass RC filter

  39. Vector diagram for the high pass Filter Leading Lagging So Vout leads (Vin-Vout) by 90 degrees. So we can calculate the filter output using Pythagoras As the frequency increases Vout moves round the circle from the bottom to the topon the left

  40. Our simplified single stage with capacitors C4 C3 C2 C1

  41. Questions?

More Related