EE3110 AEC5_Monolithic Circuit Techniques_2007

EE3110 AEC5_Monolithic Circuit Techniques_2007 - 5 5.1...

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Unformatted text preview: 5 5.1 Monolithic Circuit Techniques Current Mirrors IREF V R IC1 Q 1 + 1 IO I B1 I B2 Q 2 V ­ I REF V + − V − − VBE = R1 I REF = I C1 + I B1 + I B 2 2 ≈ I C 2 1 + β IC 2 = IO = I REF 2 1+ β VA IO Output resistance RO ≈ ro = 5.2 3­Transistor Current Source V R IREF I B3 IC1 Q 1 + 1 Q 3 IO I B1 I B2 Q 2 V ­ I REF = I C1 + IE3 1 + β3 2 ≈ I C 2 1 + β (1 + β ) 3 IC 2 = IO = I REF 2 1+ β (1 + β 3 ) A better approximation for IO ≈ IREF 5.3 Wilson Current Source V IREF I B3 IC1 Q 1 + R IO 1 Q 3 I B1 I B2 Q 2 V ­ IC 3 = IO = I REF 2 1+ β (1 + β ) Output resistance RO ≈ βro 3 2 5.4 Widlar Current Source IREF V R IC1 Q 1 + 1 IO I B1 I B2 Q 2 R E V ­ I REF ≈ I C1 = I S eVBE 1 /VT I O = I C 2 = I S eVBE 2 /VT I ⇒ VBE1 = VT ln REF I S I ⇒ VBE 2 = VT ln O I S I ∴VBE1 − VBE 2 = VT ln REF I O But from circuit, VBE1 − VBE 2 = I E 2 RE ≈ I O RE I ∴ I O RE = VT ln REF I O ' Also, RO ≈ ro 2 1 + g m 2 RE ( ) ' where, RE = RE // rπ 2 5.5 Some FET Equivalents IREF M V + V IREF + IO M 3 3 V G S3 V IO G S3 M 1 M V G S1 2 M V ­ 1 M V G S1 2 V G S2 V G S2 2­MOSFET current source MOSFET Wilson current source IO V DS V ­ JFET current source 5.6 Active Loads V Q I C2 I C0 V I 2 + V M 2 V SG + Q 1 M 1 IC1 V Q 0 O I2 IO V 1 I V M 0 I RE F O I RE F R Av = − g m ( ro 0 // ro 2 ) V V = − g m A0 // A2 I O IO − gm 1 = IO 1 + 1 V A0 V A 2 1 − VT = 1 1 + V A0 V A 2 5.7 Differential Amplifier V R V R V O1 2 + R 1 V Q 1 O2 3 I1 Q 2 V I2 Q 4 Q 3 V ­ 5.8 Level Shifter – using a current source V V R 2 I + Q 1 R 1 V Q 2 O Q 3 V ­ VO = VI − VBE − I O R1 Tutorial : Monolithic Techniques Review questions : 1­3, 5­7. 1 2 3 4 Basic current source E13.1 Modified E13.2 Widlar E13.3 Wilson W13.4 P13.1, 13.2 P13.3, 13.4 P13.6, 13.7, 13.8 P13.9, 13.10, 13.11 ...
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This note was uploaded on 01/11/2011 for the course EE 3110 taught by Professor Wingshingchan during the Fall '08 term at City University of Hong Kong.

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EE3110 AEC5_Monolithic Circuit Techniques_2007 - 5 5.1...

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