N_BJT_sedra_N10 - Bipolar Junction Transistors (BJTs) (10)...

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1 Bipolar Junction Transistors (BJTs) (10)
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2 BIPOLAR JUNCTION TRANSISTORS (BJT’s) Question 5.1 : Consider an npn transistor with v BE = 0.7 volts at i C = 1 mA. Find v BE at i C = 0.1 ma and i C = 10 mA? Answer: 0.64 Volts and 0.76 Volts Question 5.2 : Transistor of a certain type are specified to have β values in the range 50 to 150. find the range of their α values? Ans. 0.980 and 0.993 Question 5.3 : Measurement of an npn BJT in a circuit shows the base current to be 14.46 μ A, the emitter current to be 1.460 mA, and the base-emitter voltage to be 0.7 V. For these conditions, calculate α, β and I S ? Ans. 0.99, 100, 10 -15 A Question 5.4: Calculate β for two transistors for which α = 0.99 and 0.98. For collector currents of 10 mA, find the base current of each transistor? Ans. 99, 49, 0.1 mA , 0.2 mA
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3 BIPOLAR JUNCTION TRANSISTORS (BJT’s) § 5.2.1 Circuit Symbols and Conventions The physical structure used thus far to explain transistor operation is rather cumbersome to employ in drawing the schematic of a multi-transistor circuit. Fortunately, a very descriptive and convenient circuit symbol exists for the BJT. Figure 5.13(a) shows the symbol for the npn transistor; the pnp symbol is given in Fig. 5.13(b). In both symbols the emitter is distinguished by an arrowhead . Figure 5.13 Circuit symbols for BJTs.
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BIPOLAR JUNCTION TRANSISTORS (BJT’s) § 5.2.1 Circuit Symbols and Conventions This distinction is important because, as we have seen in the last section, practical BJTs are not symmetric devices. The polarity of the device ------- npn or pnp -------- is indicated by the direction of the arrowhead on the emitter. This arrowhead points in the direction of normal current flow in the emitter, which is also the forward direction of the base-emitter junction. Since we have adopted a drawing convention by which currents flow from top to bottom
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This note was uploaded on 01/29/2011 for the course EE 203 taught by Professor Gp.(r)muzaffarali during the Fall '10 term at College of E&ME, NUST.

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N_BJT_sedra_N10 - Bipolar Junction Transistors (BJTs) (10)...

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