HSI255 ‐ Seneca College
Week 4 Lecture Topics
AC Sine Waves: Vpk , VAVG , VRMS
HSI255
Reminder: Take written notes in class.
2201‐KC
Sine Waves Calculations
2
Rectification
Half‐wave:
VPK‐to‐PK = VPK ൈ 2
VAVG = VPK ൈ 0.637
Full‐wave
Bridge:
VRMS = VPK ൈ 0.707
3
Filter the Output Voltage:
4
Example Question
 A sine wave with peak‐to‐peak voltage of 10 V is
delivered through a bridge rectifier to a load resistor.
 What is the RMS voltage across the load?
VRMS = 2.55 V
5
K.Craigs (2201)
6
1
HSI255 ‐ Seneca College
Week 4 Lecture Topics
Atomic Structure
HSI255
2201‐KC
8
Silicon Lattice – Doping
N‐type and P‐type Materials
 Q: What if you inject other types of atoms?
 P‐type = silicon lattice with missing electrons (holes)
 N‐type = silicon lattice with extra electrons (electrons)
Q: What if you place a P‐type next to an N‐type material?
9
The Diode
10
The Transistor (BJT)
 Place material NPN to get a Bipolar Junction Transistor
11
K.Craigs (2201)
12
2
HSI255 ‐ Seneca College
Week 4 Lecture Topics
The Transistor (2 Diodes)
Transistor States
 Like two back‐to‐back diodes:
1. Saturation
 Short circuit: current flows IC to IE
2. Cut‐Off
 Open circuit: no current flow
3. Active (or Reverse‐Active)
 Amplifier: proportional current flow
Transistor State is set by voltages VBE and VBC.
13
Voltages Set Transistor State
14
BJT Operating Conditions
Normal Conditions for NPN Transistor:
 Base‐Emitter is forward biased
 Base‐Collector is reverse biased
The BJT is a current amplifier.
 IE = IC + IB
 Often IB << IC, therefore IE ≈ IC
15
16
Use a Transistor as an Amplifier
Use a Transistor as a Switch
 Vcc = source voltage
 Place the desired load on the
collector side.
 Transistor goes in Saturation
 VIN = applied signal
 VOUT = output signal
Q: What is Saturation?
 IB controls the IC to IE
Q: Do we set VIN high or low?
Gain:
AV = VOUT / VIN
AP = POUT / PIN
Q: What 3 factors cause
transistor saturation?
17
K.Craigs (2201)
18
3
HSI255 ‐ Seneca College
Week 4 Lecture Topics
Example: Acts Like a Switch
Example: Saturating Q1
19
20
The Transistor (FET)
 Many other types of transistors, FET is a new category
 Field Effect Transistor – Like a hose with a clamp
HSI255
2201‐KC
21
Example: Breadboard Setup
HOMEWORK for
HSI255 Week 4
 Try solving practice problems
to find Vpk, VRMS and VAVG.
 Practice constructing circuits
on the breadboard, quickly.
 Try solving a BJT saturation
problem with an LED output.
 Answer all questions in Lab 4.
23
K.Craigs (2201)
24
4