FYSE400 ANALOG ELECTRONICS

Transcription

1 YS400 ANALOG LTONS LTU 1 ntroduction to ipolar Junction Transistor ircuits 1 NTODUTON The deal urrent-controlled urrent Source efore the detailed analyzation of transistor operation, we should examine first the circuit properties of controlled source. 1 i1 i v Ai v s - s 1 i 1 i v Ai L deal (a) current-controlled current source with (b) voltage exitation and load resistance. i 1 : input current i Ai 1 : output current (1-3) : input terminal (-3) : output terminal Parameter A is the current gain. urrent gain A relates the strength of the source to the control current. 1

2 NTODUTON The deal urrent-controlled urrent Source Unilateral behavior The current signal at the output terminals do not affect the control current. nput portion of circuit is isolated from circuit elements connected to the output. v s i1 i Ai1 s v i L 0 v s - s 1 i 1 i v Ai L v A L Ai1L vs s oltage amplification is achieved if : A L 1 v vs s 3 NTODUTON The deal urrent-controlled urrent Source s 1 A 1 i i1 v s - i 1 Ai 1 i v - L 3 3 Power dissipated by L is greater than power supplied by v s. Power gain. 4

3 NTODUTON The deal urrent-controlled urrent Source urrent-voltage characteristics The iv-characterisics is a family of curves of i versus v for different input current values i 1. 5 i The slope of the output current is zero for all ideal current sources The output current i is independent of the voltage v v i 1 0 The iv-characteristics of the ideal current-controlled current source. 5 NTODUTON The deal urrent-controlled urrent Source A switching behavior s i 1 1 Device i v s - 3 v - A circuit using the ideal current-controlled current source. 6 3

4 NTODUTON The deal urrent-controlled urrent Source A switching behavior irst we examine the iv-characteristics of the load resistor. i - v urrent i versus v urrent i versus v i v rom figure, we can write: v i v 1 v i i Slope = k v 1 i i i Slope = k v 1 v 1 Device v v 7 NTODUTON The deal urrent-controlled urrent Source A switching behavior We can write that i i Now we can draw the load line in the same picture with iv-characteristics of current source. 5 i i 15 v s - s i 1 1 i Device i v rom this picture, we find output voltages for different input currents Load line v 0 when i1 14 i A 14 v i 1 0 v when i1 0 i 0 8 4

5 NTODUTON The deal urrent-controlled urrent Source A switching behavior i slope A 5 i i Load line 13 1 t i 3 i v i 1 0 i 0 i 1 0 t i1 13 v 3 t 9 NTODUTON The deal urrent-controlled urrent Source A switching behavior Output voltage, when input voltage is a step function. v v v s s 3 i 1 The output waveform produced by step exitation. t t 10 5

6 NTODUTON The deal urrent-controlled urrent Source An amplifier behavior s 1 i A simple amplifier circuit using current-controlled current source. v si 11 - i 1 Ai 1 v The voltage 11 is used to bias the device at an operating point Q. The total input voltage : v S 11 m sint v si 1 m 1Q sint 11 s Where m is an amplitude of sinusoidal input voltage v si. Where 1Q is an input bias current at bias point Q (when v si = 0). 11 NTODUTON The deal urrent-controlled urrent Source An amplifier behavior i 1 5 i i Load line Q i i 3 11 t 1 0 Q 11 v i 1 0 i 1 t lipping v (Notice, that m < 11, for a full sinusoidal responce.) Mainly maximum m depends on t Output voltage 1 6

7 NTODUTON Transistor structure Junction transistor ipolar transistor The bipolar junction transistor is constructed with three doped semiconductor regions separated by two pn junctions, as shown in epitaxial planar structure in igure 6(a). Aluminum contacts (collector) (collector) mitter ase ollector Substrate (base) n p n ase-ollector junction ase-mitter junction (base) (emitter) (emitter) (a) (b) (c) p n p A basic bipolar junction transistor construction. 13 NTODUTON Transistor symbols (excluded special-purpose transistors) (collector) (collector) (base) n p n (base) p n p (a) (emitter) (b) (emitter) Symbols for a basic npn- and pnp-bipolar junction transistors. 14 7

8 NTODUTON Transistor urrents Positive current convention: The assumed positive direction for terminal currents, and is into the transistor. or npn : or pnp : ollector current = positive ase current = positive mitter current = negative ollector current = negative ase current = negative mitter current = positive Terminal currents for a basic npn- and pnpbipolar junction transistors. oltage drops of pnp-transistor are negative. 15 NTODUTON Transistor Operation (npn) Assumption : Transistor is biased on the linear active region. (diffusion) Majority carriers. (electrons) ma ollector n ase p mitter n Narrow depletion region due to the forward-biased pn-junction. (drift) Minority carriers. (electrons) O na - µa Leakage current. Depends on temperature Wide depletion region due to the reverse-biased pn-junction. µa ma 16 8

9 NTODUTON Transistor Operation (pnp) Assumption : Transistor is biased on the forward active region. (diffusion) Majority carriers. (holes) ma ollector p ase n mitter p Narrow depletion region due to the forward-biased pn-junction. (drift) Minority carriers. (holes) na - µa O Leakage current. ma Depends on temperature. Wide depletion region due to the reverse-biased pn-junction. µa 17 NTODUTON The bers-moll epresentation Of The JT pnp Large-signal (bers-moll) representation of a pnp transistors. D D D D ommon-base configuration pnp D D D D The two back-to-back diodes represent the junction of the bipolar transistor. The current assosiated with the emitter-base diode. The current assosiated with the collector-base diode. Portion of D that is coupled through the base to emitter. Portion of D that is coupled into the collector. Two controlled sources indicates the coupling between junctions. The emitter node : 0 D D The collector node : 0 D D D D bers-moll quations for pnp-transistor D D S S e 1 e 1 S e 1 e 1 S S and S are reverse saturation currents of the emitter-base and collector-base junctions, respectively. 18 9

10 NTODUTON The bers-moll epresentation Of The JT pnp S S and are functions of doping densities and transistor geometry. They are related by : S S eciprocity relation and (rom Millmann, rabel) S, S Order of and depens on respective junction areas. Since and are less than unity, not all current from one diode is coupled to the other junction rom KL : Subscript means forward transmission from emitter to collector for pnp-transistor. Subscript means reverse transmission from collector to emitter for pnp-transistor. 0 Note! orward active 19 NTODUTON The bers-moll epresentation Of The JT npn Large-signal (bers-moll) representation of a npn transistors. D D D D ommon-base configuration npn D D D D The two back-to-back diodes (reversed direction) represent the junction of the bipolar transistor. The current assosiated with the emitter-base diode. The current assosiated with the collector-base diode. Portion of D that is coupled through the base to emitter. Portion of D that is coupled into the collector. Two controlled sources (reversed direction) indicates the coupling between junctions. The forward diode currents needs also a forward bias voltage. Since the directions of diodes are reversed, we must insert a minus sign before and. We must also take notice of reversed direction of two controlled sources in current equations for emitter an collector nodes. 0 10

11 NTODUTON The bers-moll epresentation Of The JT npn bers-moll quations for npn-transistor The emitter node : 0 D D The collector node : 0 D D D D D D S S e 1 e 1 S e 1 e 1 S S and S are reverse saturation currents of the emitter-base and collector-base junctions, respectively rom KL : Subscript means forward transmission from collector to emitter for npn-transistor. Subscript means reverse transmission from emitter to collector for npn-transistor. 0 Note! orward active 1 NTODUTON The bers-moll epresentation Of The JT Large-Signal urrent Gain npn orward-biased transistor. Short-circuited. 0 0 npn-transistor 0 T e 1 T S e 1 S D D D D S S -M equations for npn-transistor e 1 S e 1 e 1 e 1 S ommon-base forward short-circuit current gain. The measurement of α The measurement of S 0 11

12 NTODUTON The bers-moll epresentation Of The JT Large-Signal urrent Gain npn everse-biased transistor. orward-biased. 0 0 Short-circuited. 0 D D T e 1 T S e 1 S D D S S -M equations for npn-transistor e 1 S e 1 e 1 e 1 S The measurement of S The measurement of α ommon-base reverse short-circuit current gain. 0 oles of emitter and collector are reversed 3 NTODUTON The bers-moll epresentation Of The JT Large-Signal urrent Gain D D D D S S e 1 S e 1 e 1 e 1 S pnp Short-circuited. 0 0 orward-biased. e T 1 T e 1 0 S 0 S ommon-base forward short-circuit current gain. Same for npn-jt orward-biased. 0 Short-circuited. 0 0 T e e 1 1 S 0 S ommon-base reverse short-circuit current gain. Same for npn-jt 4 1

13 NTODUTON The bers-moll epresentation Of The JT and Short-circuited orward-biased. 1 0 rom KL : 0 1 where 1 ommon-emitter forward short-circuit current gain. Typical values : And in reverse condition : 1 ommon-emitter short-circuit reverse current gain. Typical values : NTODUTON The bers-moll epresentation Of The JT ma (a) The npn-jt collector current versus base current in forwardactive region. A D-current gain β (b) Typical variation of a JT forward-active current gain with collector current for several junction temperatures. 6 13

14 NTODUTON Operation Modes in JT orward-active utoff Saturation everse-active Junction bias condition mitter-base ollector-base orward everse everse everse orward orward everse orward 7 NTODUTON Operation Modes in JT orward-active utoff Saturation everse-active Junction bias condition mitter-base ollector-base orward everse everse everse orward orward everse orward orward active orward-active region is useful for analog circuits. Nearly constant-current region (arly voltage). orward-active current gain: 100 xample of common-emitter output characteristics of npn-transistor (NA) for forward-active mode. xample of common-base output characteristics of npn-transistor (NA) for forward-active mode. 8 14

15 NTODUTON Operation Modes in JT orward-active utoff Saturation everse-active Junction bias condition mitter-base ollector-base orward everse everse everse orward orward everse orward ( 3 4 ( 3 ( 1 utoff region ( 0 0 ) ) ) ) n the cutoff region the collector current is zero. ( 0.5 ) 0 9 NTODUTON Operation Modes in JT Saturation region orward-active utoff Saturation everse-active Junction bias condition mitter-base ollector-base orward everse everse everse orward orward everse orward n the saturation region the is almost zero and independent of the collector current. ( ) xample of common-emitter output characteristics of npn-transistor (NA) for saturation region

16 NTODUTON Operation Modes in JT orward-active utoff Saturation everse-active Junction bias condition mitter-base ollector-base orward everse everse everse orward orward everse orward ( A ) n the reverse-active region the collector current and are negative. The role of emitter and collector are interchanged. everse-active current gain: everse active xample of common-base output characteristics of npn-transistor (NA) for reverse-active mode. 31 NTODUTON Maximum Transistor atings Maximum ratings max Maximum power dissipation curve SOA reakdown region O 40 O 60 O 6 00mAdc P D 0.65W Derate 5mW / T J T stg Steady state power dissipation Safe Operating Area SOA max To example data sheet The npn-jt collector characteristics. 3 16

17 NTODUTON Maximum Transistor atings Maximum Power Dissipation P D max P D(max) The P (Dmax) is specified at ambient temperature 5. P D(max) Use derating factor for higher temperatures. max With higher voltages, JT has also nd breakdown limitation. The second breakdown leads to an irreversible failure in bipolar power transistors. Large junction area max Steady state power dissipation See an example of SOA N3055 urrent concentrates to a local area A local heating leads to a destruction. Pulsed mode power dissipation 33 NTODUTON Maximum Transistor atings Thermal haracteristics Assumption: The thermal resistance between case and heatsink is low. t depends on quality of thermal connection between case and heatsink. No Heatsink Junction temp. With Heatsink Heatsink T J ase PD JA J Junction to ase Device T A Ambient temperature Hs ase to Heatsink Heatsink to Ambient HsA quivalent circuit of the thermal connection between JT and surrounding environment. (Steady State nd.) J TO TO W ase TO-0 TO-3 Hs JA HsA 34 17

18 NTODUTON Maximum Transistor atings Thermal haracteristics Thermal esistance between Junction and Transistors ase J On steady state condition: P D max T J max T J J T TJ T = ase Temperature T Jmax = Maximum Junction Temperature P D T J J T 35 NTODUTON Maximum Transistor atings Thermal haracteristics Thermal esistance between Junction and Air P D max T T A = Ambient Temperature J max JA T JA A Junction JA through case to air T A TJ xample : N3903 T JA J J max 00/W 83.3/W 150 Transistors power dissipation is : Ambient temperature is : P T D A 00mW 30 P D T J JA alculate transistors junction temperature. T T J A JA PD W 70 W OK T A 36 18

19 NTODUTON Maximum Transistor atings Maximum Power Dissipation P D mw P P D(max) slope 1 J No heat sink Derating factor mw/ mw T T J max ase temperature The maximum power dissipation at higher temperature. xample : P D max 1.5W at 5 asetemp. Derating factor 1mW / ind a maximum power dissipation at case temperature : 100 P D max 1.5W 1mW / mW 37 NTODUTON Maximum Transistor atings P D max J T j(max) T Hs A HsA Low thermal resistance results to a high power dissipation limit. Maximum Power Dissipation with Heatsink Heatsink ase T J max J Hs HsA PD max TA Device J Hs f transistor is supported only by its leads, heat energy can mainly flow from case to surrounding environment by two ways : ADATON and A ONON. adiation and convection are inefficient heat transfer methods. HsA JA J Hs HsA High volume "device" 38 19

20 NTODUTON Maximum Power Dissipation with Heatsink xample : GA heatsink Heating element case : TO0 0 0,05 0,5 1,5 0,05 0,1 1,0,1 0,1 0,,0 5,7 0,4 0,3 3,0 9,5 0,9 0,4 4,0 36, 1,6 0,5 5,0 44,3,5 0,71 7,1 63,5 5,0 0,9 9,1 84,1 8, 0,97 9,8 94,4 9,5 1,1 11,1 110,7 1, 40mm 40mm Heatsink ase esistor 39 NTODUTON Maximum Power Dissipation with Heatsink Thermal resistance of the heatsink 100 HsA 7 W Natural Assumption: Natural cooling xample : GA heatsink Heating element case : TO0 The thermal resistance between case and heatsink is low. f device (case TO0) has 10W power dissipation, the case temperature T HsA 4, 5 W orced an power 0.54W orced cooling an power 0.54W, 40mm X 40mm f device (case TO0) has 10W power dissipation, the case temperature T

21 NTODUTON Maximum Power Dissipation with Heatsink xample : TO0/18 heatsink Heating element case : TO rom datasheet : thermal resistance of the heatsink HsA 17 W Measured thermal resistance of the heatsink HsA W Natural cooling : xample : TP9 Power dis. : 4.97W f device (case TO0) has 5W power dissipation, the case temperature is T J T / W 4.97W 4. / W 4.97W NTODUTON Heat transport xample : ound Heat pipe Thermal resistance of pipe taken at 70deg working temperature (adiabatic), under horizontal orientation, evaporator section 15mm, and condensation section 60mm rom technical data xample Heating element case : TO0 T T condencer running water P D 44. 4W 4 1

22 NTODUTON Heat transport 43 NTODUTON Heat transport 44

23 NTODUTON Heat transport xample : lat Heat pipe 45 NTODUTON Transistor ategories Power transistors Typically can handle large currents ( > 1A ) and/or large voltages General-Purpose transistors Small-Signal transistors Typically used in low- and medium-power amplifiers and switching circuits. f-transistors transistors are designed to operate at extremely high frequencies. (communication systems). 46 3

24 NTODUTON Transistor ategories Typical cases for Power Transistors TO-0 4 XAMPLS TP : ase : ollector 3 : mitter 4 : ollector TP30 TO-3 ollector N NTODUTON Transistor ategories Typical cases for General-Purpose Transistors ollector Plastic pacage TO-18 Metal can TO-9 ndicates an emitter pin 546 NA 48 4

25 NTODUTON Transistor ategories Typical cases for -Transistors 49 NTODUTON The nd of Part

26 NTODUTON An example of measurement of α 0 A A rom KL : 0 -M quations 0 S S e e T e 1 1 S Note! ase current is positive mitter current is negative mitter-ase voltage is negative for forward bias. To previous slide 1 51 NTODUTON An example of measurement of S D D D D S S -M equations for npn-transistor e 1 S e 1 e 1 e 1 S 0 e 1 e S S S Note! e T mitter-ase voltage is negative for forward bias. 0 A A - To previous slide mitter current is negative 5 6

27 NTODUTON An example of measurement of S D D D D S S -M equations for npn-transistor e 1 S e 1 e 1 e 1 0 e T 1 T e 1 S S S e T S 0 A Note! mitter-ase voltage is negative for forward bias. A - To previous slide mitter current is negative 53 NTODUTON An example of measurement of α eciprocity relation S S S S To previous slide 54 7

28 NTODUTON -output haracteristics of N for everse-active Mode. NPUT SD OUTPUT SD mitter urrent 0 = -1mA = -ma ma = -3mA 4mA = -7mA = -9mA oltage To previous slide 6mA NTODUTON -output haracteristics of N for orward-active Mode. NPUT SD OUTPUT SD 8mA ollector urrent = -9mA 6mA 4mA = -3mA ma = -ma To previous slide = -1mA oltage

29 NTODUTON -output haracteristics of N for orward-active Mode. NPUT SD OUTPUT SD ollector urrent 5mA orward-active = 100µA = 90µA = 80µA = 70µA = 60µA = 50µA 8mA 4mA = 40µA = 30µA = 0µA To previous slide 0 = 10µA oltage NTODUTON -output haracteristics of N for Saturation egion. NPUT SD OUTPUT SD ollector urrent 5mA Saturation region = 100µA = 90µA = 80µA = 70µA = 60µA = 50µA 8mA 4mA = 40µA = 30µA = 0µA To previous slide 0 = 10µA oltage