Junction Transistor Amplifier Lesson-6: Detailed Study of Currents in a Transistor, Transistor Alfa and Characteristics of transistor in common base, common emitter and common collector configuration 2008 Junction Transistor Lesson 6- ", Raj Kamal, 1
1. Revision 2008 Junction Transistor Lesson 6- ", Raj Kamal, 2
PNP Three configurations PNP PNP I B I E I C BJT Common Base configuration BJT Common Emitter configuration BJT Common Collector configuration 2008 Junction Transistor Lesson 6- ", Raj Kamal, 3
2. Current Components due to holes and electrons in E, B, and C regions 2008 Junction Transistor Lesson 6- ", Raj Kamal, 4
PNP forward biased junction I E Majority Carrier I EN I EP 1 5 4 I BE I C holes electrons I E = I EP + I EN = 1 + 2 + 5 I B = I BR + I BE = I BR + I EN = (4 + 5) I C = I EP I BR = 2 I B I BR I BR Minority Carrier 2 3 Electron flux Hole flux and current 2008 Junction Transistor Lesson 6- ", Raj Kamal, 5
Current components 1 = hole current lost due to recombination in base, I BR 2 = hole current collected by collector, ~ I C 1 + 2 = hole part of emitter current, I EP 5 = electrons injected across forward biased E-B junction, ( I BE ); same as electron part of emitter current, I EN 4 = electron supplied by base contact for recombination with holes lost, I BR (= 1) 3 = thermally generated e & h making up reverse saturation current of reverse biased C-B junction. (generally neglected) 2008 Junction Transistor Lesson 6- ", Raj Kamal, 6
Formula for Collector Current Components I C = I Cmajority + I COminority Leakage component I CO = Collector Current with emitter terminal open (not connected) 2008 Junction Transistor Lesson 6- ", Raj Kamal, 7
3. Transistor Alpha 2008 Junction Transistor Lesson 6- ", Raj Kamal, 8
Alpha dc dc = I C I E = I C.. (1) I E dc 0.90 to 0.998 Leakage component I C = dc I E + I CB0..(2) 2008 Junction Transistor Lesson 6- ", Raj Kamal, 9
means small change in Alpha ac (Common base short circuit amplification factor) ac = I C I E = I C.. (1) I E ac dc 0.90 to 0.998 V CB = constant Leakage component I C = dc I E + I CB0..(2) 2008 Junction Transistor Lesson 6- ", Raj Kamal, 10
4. Input and Output Characteristics of transistor in common base 2008 Junction Transistor Lesson 6- ", Raj Kamal, 11
Emitter characteristics (input Characteristics) of base-emitter emitter region amplifier in the dc mode Common base I E (ma) Active Region Active Region V BE I E V BE (V) 0.7 V V BE (V) 2008 Junction Transistor Lesson 6- ", Raj Kamal, 12
Active region V BE 0.7 v V BE Active 0.7 v region V BE 0.7 v V BE 0.7 V BE v 0.7 v Saturation region V BE OR << 0.7 V Output Characteristics Common Base 2008 Junction Transistor Lesson 6- ", Raj Kamal, 13
First Approximation Relationship between I C and I E I C I E BJT Common Base configuration 2008 Junction Transistor Lesson 6- ", Raj Kamal, 14
Biasing Common Base V EE V CC V EE V CC I B = 0 ma I B = 0 ma 2008 Junction Transistor Lesson 6- ", Raj Kamal, 15
Amplifying action Common Base 2008 Junction Transistor Lesson 6- ", Raj Kamal, 16
Input i i input = v input / R i = 20 mv = 1 ma 20 2008 Junction Transistor Lesson 6- ", Raj Kamal, 17
Current iinput transfers from a low R i circuit to high R o circuit ac = 1, i C = i E i L = iinput = 1 ma v L = I L. R = 1 ma. 5 k = 5 V Voltage Amplification = v L /vinput = 5 V 20 mv Generally 50 to 300 = 250 2008 Junction Transistor Lesson 6- ", Raj Kamal, 18
5. Input and Output Characteristics of transistor in common emitter 2008 Junction Transistor Lesson 6- ", Raj Kamal, 19
Base-emitter emitter region amplifier in the dc mode Input Characteristics (also base characteristics) in common emitter amplifier I B ( A) V CE = 1V V BE (V) V CE = 10V V CE = 20V Active Region 0.7 V V BE I B V BE (V) Active Region 2008 Junction Transistor Lesson 6- ", Raj Kamal, 20
90 A 70 A 50 A 30 A Active region I B = 10 A Saturation region I B = 0 A I CE0 I CB0 Cut-off region region Output Characteristics (also called collector characteristics) of Common Emitter 2008 Junction Transistor Lesson 6- ", Raj Kamal, 21
pnp transistor as common emitter amplifier I C C I B B E I E I B R B B + I C p n p E C I E R C I C 2008 Junction Transistor Lesson 6- ", Raj Kamal, 22
npn transistor in a simple circuit, known as common-emitter amplifier 2008 Junction Transistor Lesson 6- ", Raj Kamal, 23
BJT Common emitter configuration Relationship between I C and I B Leakage current I B = I C I E I C = I E + I CB0 I C = ( I C + I B ) + I CB0 (1 ) I C = I B + I CB0 I C = /(1 ) I B + I CB0 /(1 ) = Current gain = [ I C / I B ] at constant V CE 2008 Junction Transistor Lesson 6- ", Raj Kamal, 24
I CEO If = 0.996 then when at I B at 0 A I C = 0.996/(0.004). 0 A + I CB0 /(0.004) = I CB0 /(0.004) = 250 I CB0 I C / I CB0 = 250 at I B = 0 I CEO = I CBO / (1 - ) at I B = 0 For linear very small distortion amplifier cut-off for common emitter configuration is at I C = I CEO 2008 Junction Transistor Lesson 6- ", Raj Kamal, 25
pnp transistor as common emitter amplifier at Cut-Off I C = I CE0 I B = 0 I C C B E I CE0 I B R B B + I C p n p E C I E R C I C 2008 Junction Transistor Lesson 6- ", Raj Kamal, 26
6. Input and Output Characteristics of transistor in common collector 2008 Junction Transistor Lesson 6- ", Raj Kamal, 27
Base-collector region amplifier in the dc mode Input Characteristics (also collector characteristics) in common collector amplifier I C (ma) V EC = 1V V BC (V) V EC = 10V V EC = 20V Active Region 0.7 V V BC I C V BC (V) Active Region 2008 Junction Transistor Lesson 6- ", Raj Kamal, 28
I E 9 ma 7 ma 5 ma 3 ma Active region Saturation region I C = 1 ma I C = 0 ma I E I EC0 Cut-off region Output Characteristics (also called emitter characteristics) of Common Collector 2008 Junction Transistor Lesson 6- ", Raj Kamal, 29
pnp transistor as common collector amplifier I B I E E B C I C I B B I E p n p E R E I E + C I C 2008 Junction Transistor Lesson 6- ", Raj Kamal, 30
BJT Common collector configuration Relationship between I C and I E Leakage current I B = I E I C I E = I C / + I EC0 I E = ( I C / ) + I EC0 I E = 1 I C + I EC0 Current gain = [ I E / I C ] at constant V CE 2008 Junction Transistor Lesson 6- ", Raj Kamal, 31
I CEO If = 0.996 then when at I B at 0 A I E = (0.996) 1. I C ma I E / I C 1 at I B = 0 For linear very small distortion amplifier cut-off for common collector configuration is at I E = I C + I ECEO 2008 Junction Transistor Lesson 6- ", Raj Kamal, 32
I B 0 pnp transistor as common collector amplifier at I CE0 B E + I C I CE0 I B C I C B p n Very High p Impedance at input E C I E R C I C low Impedance at input Current i input transfers from a high Ri circuit to low R o circuit 2008 Junction Transistor Lesson 6- ", Raj Kamal, 33
7. Transistor Beta 2008 Junction Transistor Lesson 6- ", Raj Kamal, 34
Beta dc dc = I C I B = I C.. (1) I E dc 50 to 400 range Leakage component I C = dc I B + I CE0..(2) 2008 Junction Transistor Lesson 6- ", Raj Kamal, 35
means small change in Beta ac (Common emitter forward current open circuit amplification factor) ac = I C I B = I C.. (1) I B ac dc 50 to 400 V CE = constant Leakage component I C = dc I B + I CE0..(2) Related to h FE 2008 Junction Transistor Lesson 6- ", Raj Kamal, 36
8. Relation Between Transistor Alpha and 8. Relation Between Transistor Alpha and Beta 2008 Junction Transistor Lesson 6- ", Raj Kamal, 37
BJT Alpha and Beta I E = I C + I B I C / = I C + I C / 1/ = 1 + 1 / ; = / ( + 1) = / (1 ) I C = I B I E = I B ( + 1) 2008 Junction Transistor Lesson 6- ", Raj Kamal, 38
BJT Alpha and Beta I CE0 = I CB0 / (1 ) 1/ = 1 + 1 / ; + 1= 1/ (1 ) ICE0 ICB0 2008 Junction Transistor Lesson 6- ", Raj Kamal, 39
Summary We learnt Current components in a transistor Input and output circuit characteristics in Three configurations- Common base, common emitter and Common collector Alfa dc and alpha ac Beta and beta ac 2008 Junction Transistor Lesson 6- ", Raj Kamal, 40
End of Lesson 6 2008 Junction Transistor Lesson 6- ", Raj Kamal, 41