1. TRANSISTORS
ThinkLABS
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2. TRANSISTORS
 Fundamental building block
of modern day electronics
 Used mostly as an amplifier
or switch
 Classified into two
categories:
 BJTs
 FETs
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3. TRANSISTORS: BJTS
 Bipolar Junction Transistors (BJTs) available in two
flavors
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4. TRANSISTOR ANALOGY
• Control a BIG flow of current with
a SMALL flow of current.
• Working as a Switch.
• Amount of current flow is Limited.
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5. NPN AS A SWITCH
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6. PNP AS A SWITCH
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7. TRANSISTORS
 How do we select the right transistor?
 Define and Calculate requirements
 Voltage
 Current
 Gain
 Refer datasheets
 Check availability
 Test
 Use
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8. TRANSISTORS
 How do we read transistor datasheets?
Decisive Parameters:
 Max collector-emitter voltage (Vce)
 Peak/Continuous collector current (Ic)
 DC current gain
 Transition frequency
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9. DATASHEET: PN2222
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10. TRANSISTORS
 Commonly available packages
TO-18 TO-92 TO-220 TO-3
Plastic package Metal package Plastic package Metal package
used for low used for low with heat-sink used for high
power power used mostly for power
transistors transistors with high power transistors
better thermal transistors
dissipation
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11. TRANSISTORS
 Commonly available transistors
Transistors Max Peak Collector DC current Cost Transition
Voltage Current (Ic) gain hFE(min) (Rs.) Frequency (Ft)
NPN PNP
(Vce)
2N2222 2N2907 30 800mA 100 2 300 MHz
2N3904 2N3906 40 200mA 100 2 300 MHz
BC546 BC556 65
BC547 BC557 45 100mA 300 2 100 MHz
BC548 BC558 30
TIP140 TIP145 60 10A 1000 40
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12. EXPERIMENTS
Transistor as a switch: 2N2222
Driving a LED
E B C
Rb = 1K
Rc = 500 to 1K
Calculations:
Ib= (Vin – 0.7)/Rb
Ic (max)= Ib X Hfe
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13. EXPERIMENTS
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14. ANY QUESTIONS?
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