1. Chapter 23
ELECTRONICS

2. Electronics is the study of electricity and circuits using small components such as semiconductor devices

3. Multimeters are used in electrical circuits to read:

4. Multimeters are used in electrical circuits to read:
DC/AC voltage

5. Multimeters are used in electrical circuits to read:
DC/AC voltage
DC/AC current

6. Multimeters are used in electrical circuits to read:
DC/AC voltage
DC/AC current
resistance

7. Multimeters are used in electrical circuits to read:
DC/AC voltage
DC/AC current
resistance
The latest multimeters are auto-ranging, that is, they are able to automatically sense the correct measurement range and produce an appropriate reading.

8. Power supply
power packs are generally used as laboratory power supplies
IT IS IMPORTANT THAT THE LEADS DO NOT TOUCH AND THE INSTRUMENT’S VOLTAGE IS SET TO THE LOWEST VALUE BEFORE IT IS SWITCHED ON

9. Cathode Ray Oscilloscope
uses an electron beam which strikes the face of the cathode ray tube
the electron beam passes through vertical deflection plates whose voltage is proportional to the input voltage being measured
the beam also passes through a set of horizontal deflection plates which give a sweep time (time for beam to travel from the left to right of the screen)
the CRO allows a visual display of the changing voltage and permits measurements of it to be made. It gives VPP for AC instead of the VRMS of multimeters

10. Students should neatly draw the circuit diagrams (P 505) for the potentiometer electromagnetic speaker PN diode NPN transistor PNP transistor light emitting diode (top diagram) light dependent resistor

11. A capacitor is a “storage tank” for electrons
it consists of two conducting plates separated by an insulating material (the dielectric)
information such as capacitance, tolerance and working voltage are written on the outside of the capacitor

12. A capacitor
dielectric
metal plate
If a DC voltage supply is connected to the capacitor, current will flow to the metal plates

13. When a capacitor is fully charged:
the two conducting plates have an equal and opposite charge
the voltage across the capacitor equals the supply voltage, Vs
no further flow of DC current occurs

14. The capacitance, C of the system is defined as the amount of charge in coulombs, Q, stored on each plate when the voltage, V, across the plates is 1 volt Q
C =
Farads V

15. Capacitors are normally rated in microfarads
typical capacitors in electronics range in value from one microfarad to one thousand microfarads

16. AC waveform analysis

17. AC waveform analysis
when we study AC voltage on the CRO, there appears a range of magnitudes for the voltage (see figure 23.2)

18. AC waveform analysis
when we study AC voltage on the CRO, there appears a range of magnitudes for the voltage (see figure 23.2)
the graph of voltage Vs. time is called a waveform (in this case an AC waveform) This graph is a sine wave.

19. AC waveform analysis
when we study AC voltage on the CRO, there appears a range of magnitudes for the voltage (see figure 23.2)
the graph of voltage Vs. time is called a waveform (in this case an AC waveform) This graph is a sine wave.
the DC waveform is a straight line

20. the peak voltage, VP , is the vertical amplitude from zero to the top of the sine wave

21. the peak voltage, VP , is the vertical amplitude from zero to the top of the sine wave
the peak to peak voltage, VPP , is taken from the top of a crest to the bottom of a trough

22. the peak voltage, VP , is the vertical amplitude from zero to the top of the sine wave
the peak to peak voltage, VPP , is taken from the top of a crest to the bottom of a trough
the most common way to describe a waveform magnitude is the root mean square voltage, VRMS

23. VRMS = 0.7 VP

24. VRMS = 0.7 VP
VRMS is a most useful way to describe AC voltages because the power dissipated in a resistor by any RMS voltage over a complete cycle is identical to the power dissipated in the same resistor by an equivalent DC voltage

25. Resistors

26. Resistors
first
number

27. Resistors
first
number
second number

28. Resistors
first
number
second number
third number

29. Resistors
tolerance %
first
number
second number
third number

30. Resistors tolerance % this resistor: first number second number
third number

31. Resistors tolerance % this resistor: 2500  5% - first number+
this resistor: 2500  5% -
first
number
second number
third number

32. Semiconductor Devices

33. Semiconductor Devices
semiconductors are elements which have some free electrons available for conduction

34. Semiconductor Devices
semiconductors are elements which have some free electrons available for conduction
when electrons break away from their nucleus, they leave behind a fixed ‘hole’ into which a free electron may drop

35. Semiconductor Devices
semiconductors are elements which have some free electrons available for conduction
when electrons break away from their nucleus, they leave behind a fixed ‘hole’ into which a free electron may drop
these ‘electron-hole pairs’ are being continuously created and destroyed in the crystal lattice

36. Semiconductor Devices
semiconductors are elements which have some free electrons available for conduction
when electrons break away from their nucleus, they leave behind a fixed ‘hole’ into which a free electron may drop
these ‘electron-hole pairs’ are being continuously created and destroyed in the crystal lattice
the electron-hole pairs are able to conduct electricity. This is called intrinsic conduction

37. The conduction of semiconductors can be improved by adding small amounts of impurities to the crystal

38. The conduction of semiconductors can be improved by adding small amounts of impurities to the crystal
this process is called doping

39. The conduction of semiconductors can be improved by adding small amounts of impurities to the crystal
this process is called doping
N-type silicon has elements from group V of the Periodic Table added. Since these atoms donate extra electrons we say that the majority charge carriers are electrons

40. The conduction of semiconductors can be improved by adding small amounts of impurities to the crystal
this process is called doping
N-type silicon has elements from group V of the Periodic Table added. Since these atoms donate extra electrons we say that the majority charge carriers are electrons
doping with group III elements creates extra ‘holes’ in the lattice. This is P-type silicon. The majority charge carriers are ‘holes’ while the electrons are minority charge carriers

41. When a piece on N-type silicon is fused to a piece of P-type silicon a PN junction is formed
some electrons from the N-type silicon drift over to combine with holes in the P-type silicon
this produces a small potential difference which acts as a barrier to other electrons
the area in which this barrier forms is called the depletion layer

42. This PN junction conducts in one direction only under normal conditions

43. This PN junction conducts in one direction only under normal conditions
if this PN junction diode is set up in a circuit with the P-type silicon positive and the N-type negative, it will conduct electricity.

44. This PN junction conducts in one direction only under normal conditions
if this PN junction diode is set up in a circuit with the P-type silicon positive and the N-type negative, it will conduct electricity.
this is called forward biasing

45. This PN junction conducts in one direction only under normal conditions
if this PN junction diode is set up in a circuit with the P-type silicon positive and the N-type negative, it will conduct electricity.
this is called forward biasing
if the P-type silicon is negative and the N-type positive conduction is stopped. This is called reverse biasing

46. This PN junction conducts in one direction only under normal conditions
if this PN junction diode is set up in a circuit with the P-type silicon positive and the N-type negative, it will conduct electricity.
this is called forward biasing
if the P-type silicon is negative and the N-type positive conduction is stopped. This is called reverse biasing
a PN junction diode can be made to conduct in reverse bias if a large voltage is applied. This is called avalanche breakdown and is damaging to the diode

47. AC Rectification
certain combinations of diodes can change AC to DC current
learn the circuit diagrams for half and full wave rectification and capacitor smoothing. You should also be able to describe how these circuits work and how they affect voltage and current