YSE400 ANALOG ELECTONCS LECTUE 3 Bipolar Sub Circuits 1
BPOLA SUB CCUTS Bipolar Current Sinks and -Sources Transistor operates in forwardactive region. < < sat CE CN max CE < < + BN CN BN max CE N N N Current sink Current source Current sink with higher output resistance
BPOLA SUB CCUTS Bipolar Current Sinks and -Sources NPN-Current Sink OUT C α ES e BE / T 1 + CE A CC OUT OUT Collector characteristics CN + BE - N α ES e BE / T CN 3
BPOLA SUB CCUTS Bipolar Current Sinks and -Sources PNP-Current Source BE + CC - OUT Collector characteristics OUT + - CN α ES e BE / T N CC CN 4
BPOLA SUB CCUTS Bipolar Current Sinks and -Sources NPN-Current Sink with emitter resistance CC OUT CN BN + BE - OUT α C BN E BE E N 5
BPOLA SUB CCUTS Bipolar Diode Connected oltage Source 6
BPOLA SUB CCUTS Bipolar Diode Connected oltage Source CC i OUT E i 1 i OUT + v OUT i B i C v OUT T ln α E ES - v OUT E v OUT T E + i ln α ES OUT 0.6 < vout < 0.7 when ib << E and iout ( β >> 1) 7
BPOLA SUB CCUTS Bipolar Diode Connected oltage Source CC E v OUT v OUT 1 8
BPOLA SUB CCUTS Current Mirror Assumptions dentical tansistors CE1 CE BE f β β CC >>1 then BE β + CC BE 9
BPOLA SUB CCUTS Current Mirror BE depends on the ambient temperature : -.m/ C Sensitivity of reference current is low if we have CC >> BE BE BE 1 ( ) 1 CC BE eference current depends on the CC, and BE. esistor can be replaced by constant current source E Constant current sink 10
BPOLA SUB CCUTS Current Mirror f CE1 > CE CE 1 >> 0.7 β β + 1 + CE1 A 11
BPOLA SUB CCUTS Current Mirror Transistors have different emitter areas A1 and A ES1 ES A A 1 C α α ES1 ES e e BE BE / / T T ( 1 + CE1 A ) ( 1 + ) CE A A1 A >> β >> OUT E A f we assume that CE and 1 1
BPOLA SUB CCUTS Multiple Output Current Mirror (Multiple output current sink) dentical transistors All output transistors has same base current. N OUT N + 1 1 + β Difference between reference and output current is proportional to the number of outputs. N OUT B(1 + N ) 13
BPOLA SUB CCUTS Modified Multiple Output Current Mirror (Multiple output current sink) Emitter follower is used to supply base current. On 1 + N 1 + β N ( β + 1) educed difference between reference and output current. N OUT B 1 + N 1 + β 14
BPOLA SUB CCUTS Multiple Output Current Mirror (Multiple output current sink) Multiple Collector BJT Different values of sink currents On. Output current depends on the effective value of collector area. O1 N O N O N max ON O 10 min N O 15
BPOLA SUB CCUTS Widlar Current Source Low output currents with practical resistance values. Assumptions CE1 CE Early voltage A is high. High output resistance o r + o o ( 1 g ) m E C e ( )/ / T BE β 1 + β BE1 T e CC BE C BE E β 1 + β T ln C T ln C C 10 BE 60m C 100 BE 10m 16
BPOLA SUB CCUTS Widlar Current Source Widlar Current Source E1 > E Current Mirror E1 E > C E E1 17
BPOLA SUB CCUTS Wilson Current Source Wilson Current Source High output resistance o β β ( β + ) ( β + ) + N β β ( β + ) CC ( β + ) + BE See Modified Multiple Output Current Sink N1 β β ( β + 1) ( β + 1) + N β β ( β + 1) CC ( β + 1) + BE 18
BPOLA SUB CCUTS Differential Stage (Emitter-coupled pair) Generic Differential Stage Assumption: nput currents i 1 i 0 BAS is Constant Current Source 1 v1 v Power Supply typically + v i1 v i BJT or ET dentical pair Sub Circuit of Operational Amplifiers Emitter Coupled Logic (ECL) 19
BPOLA SUB CCUTS Differential Stage nput signals: v + 1 1 vi1 v + vi Quisent values (Ac-component is zero) v v 1 1 1 v 1 v 1 ON1 + + + L1 L ON1 ON 1 L1 v i1 v i ON + L Generic Differential Stage 1 + BAS 0 ( ) 0 Summ of currents 1 and is constant. OD ON1 ON L 1 0
BPOLA SUB CCUTS Differential Stage f ON1 is output of differential stage then: 180 phase difference N1 is inverting input N is noninverting input Differential mode N1 N N1 N 1 v 1 v v i1 v i N1 N N1 N Common mode Generic Differential Stage 1
BPOLA SUB CCUTS Differential Stage Arbitrary input voltage consists of common mode and differential mode voltages. + N1 CM DM N CM DM Where 1 1 ( N1 + N ) CM ( N1 N ) DM 1 + N1 N1 N N ( 1 + N ) CM N 1 ( N ) 1 N N N1
BPOLA SUB CCUTS Differential Stage Common Mode Gain A CM Differential Mode Gain A DM Linear system and superposition Arbitrary output voltages: A + ON1 DM DM A CM CM A + ON DM DM A CM CM Common Mode ejection atio CM CM A A DM CM Differential Amplifier n deal Case the A CM is zero 3
BPOLA SUB CCUTS Differential Stage Arbitrary output voltages ON1 A DM DM + CM CM ON A DM DM CM CM 4
BPOLA SUB CCUTS BJT Differential Stage Collector currents α ES e BE1 / T C α ES e BE / T E1 E C e ( )/ / T e 1 T D D 1 (a) Node E : E 1 + E EE 0 EE α + α C (b) 5
BPOLA SUB CCUTS BJT Differential Stage D < T "Linear" input voltage region CC (a) and (b) C α 1 + e α 1 + e EE D / T EE / D T O1 O CC α EE C O1 CC α 1 + e EE C / D T T 4 T T D O CC α 1 + e EE / C D T OD 1 1 O1 O α EEC D /T D / T 1 + e 1 + e 6
BPOLA SUB CCUTS BJT Differential Stage v N1 +9.0 v N Amplitude : 50m or 300m 3.8kΩ 3.8kΩ v N1 CQ1 6.6 CQ 6.64 Q1 v BSX0 v C BSX0 Q 9.0 v N 1.kΩ v E 1.kΩ 3.3kΩ EQ -0.69 BSX0 Q4 Q3 BSX0 9.0 Ω -9.0 Practical example 7
BPOLA SUB CCUTS BJT Differential Stage v v C Collector voltages in fully differential mode 8
BPOLA SUB CCUTS BJT Differential Stage v v C 9
BPOLA SUB CCUTS BJT Differential Stage v v nput amplitude : 50m v E nput amplitude : 300m v E 30
The End of Part 3 31