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MALVINO

SIXTH EDITION. MALVINO. Electronic. PRINCIPLES. Transistor Fundamentals. Chapter 7. V CE = V CC - I C R C. 1 k W. R C. V CE. 12 V. V CC. R B. 12 V. V BB. 100 m A. 80 m A. 60 m A. 40 m A. 20 m A. 0 m A. V CC - V CE. A graph of this equation produces a load line.

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MALVINO

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  1. SIXTH EDITION MALVINO Electronic PRINCIPLES

  2. Transistor Fundamentals Chapter 7

  3. VCE = VCC - ICRC 1 kW RC VCE 12 V VCC RB 12 V VBB

  4. 100 mA 80 mA 60 mA 40 mA 20 mA 0 mA VCC - VCE A graph of this equation produces a load line. IC = RC 14 12 10 IC in mA 8 6 4 2 6 16 2 4 10 12 0 14 18 8 VCE in Volts

  5. 12 V IC = 1 kW 1 kW RC Mental short 12 V VCC RB 12 V VBB

  6. 12 V IC = 1 kW 100 mA 80 mA 60 mA 40 mA 20 mA 0 mA This is the saturation current. = 12 mA 14 12 10 IC in mA 8 6 4 2 6 16 2 4 10 12 0 14 18 8 VCE in Volts

  7. 1 kW RC Mental open 12 V VCC RB 12 V VBB

  8. 100 mA 80 mA 60 mA 40 mA 20 mA 0 mA VCE(cutoff) = VCC 14 12 10 IC in mA 8 6 4 2 6 16 2 4 10 12 0 14 18 8 VCE in Volts

  9. 100 mA 80 mA 60 mA 40 mA 20 mA 0 mA New load line has same slope 14 12 10 IC in mA 8 6 4 2 6 16 2 4 10 12 0 14 18 8 VCE in Volts

  10. Changing RC: 1 kW 750 W RC VCE 12 V VCC RB 12 V VBB

  11. 100 mA 80 mA 60 mA 40 mA 20 mA 0 mA Smaller RC produces steeper slope 14 12 10 IC in mA 8 6 4 2 6 16 2 4 10 12 0 14 18 8 VCE in Volts

  12. 100 mA 80 mA 60 mA 40 mA 20 mA 0 mA A circuit can operate at any point on the load line. 14 12 10 IC in mA 8 6 4 2 6 16 2 4 10 12 0 14 18 8 VCE in Volts

  13. VBB - VBE IB = RB The operating point is determined by the base current. 1 kW RC 12 V - 0.7 V = 40 mA IB = 283 kW 12 V VCC RB = 283 kW 12 V VBB

  14. 100 mA 80 mA 60 mA 40 mA 20 mA 0 mA The operating point is called the quiescent point. 14 12 10 IC in mA 8 Q 6 4 2 6 16 2 4 10 12 0 14 18 8 VCE in Volts This Q point is in the linear region.

  15. 100 mA 80 mA 60 mA 40 mA 20 mA 0 mA Saturation and cutoff are non-linear operating points. 14 12 10 IC in mA 8 6 4 2 6 16 2 4 10 12 0 14 18 8 VCE in Volts These Q points are used in switching applications.

  16. Recognizing saturation • Assume linear operation. • Perform calculations for currents and voltages. • An impossible result means the assumption is false. • An impossible result indicates saturation.

  17. Base bias • The base current is established by VBB and RB. • The collector current is b times larger in linear circuits. • The transistor current gain will have a large effect on the operating point. • Transistor current gain is unpredictable.

  18. Emitter bias: 1 kW 1 kW RC VBB - VBE IC @ IE = 1.95 mA IE = RE 15 V VCC 2.2 kW RE 5 V VBB VC = 15 V - (1.95 mA)(1 kW) = 13.1 V VCE = 13.1 V - 4.3 V = 8.8 V

  19. Comparing the bias methods • Base bias is subject to variations in transistor current gain. • Base bias is subject to temperature effects. • Emitter bias almost eliminates these effects. • The transistor current gain is not required when solving circuits with emitter bias.

  20. Linear Troubleshooting • The difference between collector and emitter should be more than 1 V but less than VCC. • VBE should be 0.6 to 0.7 V. • VBE can be 1 V or more in high-current circuits. • Both open and shorted junctions are possible.

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