Chapter (3) Transistors and Integrated Circuits

1. Chapter (3) Transistors and Integrated Circuits B I P O L A R J U N C T I O N T R A N S I S T O R • BJTin contrast to the "unipolar" FET • Both minority and majority carries play significant roles. • Permits greater gain better high-frequency performance. • Alloy Structure consist of • Collector (C) n-type chip  less than 1 mm square • Base (B) p-type thinner than this paper • Emittern-type alloyed to the base • The result is a pair of pn junctions separated by a base region, npn junction transistor.

2. Chapter (3) Transistors and Integrated Circuits • Planar Structure • npnBJT • (n)  grown upon a heavily doped (n+) substrate. • oxidation of the surface • window  opened to diffuse impurities  (P) into the crystal to form the pn junction. • A smaller window for emitter in opened to diffuse emitter region (n). Biasing Parameters BJT C E  B VEB VCBiE iC iB

3. Chapter (3) Transistors and Integrated Circuits Operation • The emitter junction  forward biased VEB reduced the barrier at emitter  electrons injection into B where they are minority carriers. • The collector junction is reverse biased VCB increase the barrier at C • B is very thinmost electron pass from E to C • The net result transfer electron from E to C. • Large RL insertion in C large voltage voltage amplification • Variation of the base current iBlargeiCcurrent amplification • Switching operation used in digital signal processing.

4. Chapter (3) Transistors and Integrated Circuits • DC Behavior • E forward  C reverse biased. • iE consist  electron across npJ holes from B. • g almost unity iE nearly electrons. • avaries from 0.90 to 0.999 where a typical value is 0.98. iC = -aiE + ICBO iB = -iE -iC • Most of these electrons in B diffuse to C B is very narrow. • iC consist of iE and a very small current due to thermally generatedminority carrier ICBO

5. Chapter (3) Transistors and Integrated Circuits Common - Base Characteristics • CB configuration • B common input E output C. • The emitter-base section forward-biased diode. • Input Characteristics • Input characteristicsFig.( b)similar toFig. (a)  diodecharacteristics • The effect of VCB small • +VCB  emitter open-circuited  IE = 0 •  C section  reverse-biased junction

6. Chapter (3) Transistors and Integrated Circuits • Output Characteristics • The collector characteristic  reverse bias diode iE = - 5 mA,  iC = - aiE@ + 5 mA. • The slope of the curves in Fig C due to an effective increase in aas VCB increases. • a alwaysless 1

7. Chapter (3) Transistors and Integrated Circuits The common base configuration is not good for practical current amplification

8. Chapter (3) Transistors and Integrated Circuits

9. Chapter (3) Transistors and Integrated Circuits • Input and output  CECharacteristics • iBdepends on VBEonly . • iB = 0 iC = iCEO • a= 0.98  b= 49, • A very small increase in iB large increase in iC • A verysmall increase in a much greater change in b. Practice Problem 6-3

10. Chapter (3) Transistors and Integrated Circuits