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**BJT, Bipolar Junction Transisor**

Base Current Controls Output current Bollen

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**AGENDA BJT transistorman Transistor types Bipolar Junction Transistor**

BJT models parameters water model NPN and PNP operation modes switch open switch closed BJT linear, controlled current source active operation characteristics DC input characteristics ac input characteristics BJT DC biasing circuits base bias base bias + collector feedback base bias + emitter feedback voltage divider Bollen

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BJT, transistor man Bollen

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**Transistor Types Output current controlled by input current BJT =**

Bipolar Junction Transistor FET = Field Effect Transistor Output current controlled by input voltage Bollen

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**BJT, Bipolar Junction Transisor**

Transistor = Transfer Resistor BE Forward bias, BC Reverse bias So low ohmic high ohmic Bollen

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**BJT, Bipolar Junction Transisor**

Emitter = Sent electrons Base = Base Collector = Get electrons Bollen

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BJT, Models Bollen

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BJT, parameters Bollen

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BJT, Water model Bollen

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BJT, Water model Bollen

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BJT, NPN and PNP Bollen

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**BJT, Operation modes Cut-off and saturation; BJT is used as a switch**

Active operation Quiecent Point; BJT is used as a controlled current source, or analog amplifier Bollen

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BJT, Switch open Bollen

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BJT, Switch closed Bollen

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**BJT, Lineair, controlled current source**

Bollen

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BJT, active operation Bollen

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**BJT, characteristics DC model ac model**

DC model; Vbe = 0V Ube, Uce, Ic, Ib, Ie Capitals ac model; re = 26mV/Ie ube, uce, ic, ib, ie Low cases Bollen

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**BJT, DC input characteristics**

Vbe = 0V7 Bollen

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**BJT, AC input characteristics**

re = 26mV/Ic The dynamic resistor can be calculated by the DC current Ic Bollen

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BJT, characteristics Bollen

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**BJT, DC biasing circuits**

A base bias B base bias + emitter feedback C base bias + collector feedback D voltage divider Bollen

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**BJT, base bias, introduction**

Base current determined by Vcc, Rb and Vbe Bollen

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**BJT, base bias Calculate Ib and then Ic**

Ic directly dependent on ß variation So, for stability a “bad” circuit Bollen

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**BJT, base bias load line Q-point = Quiecient point = Working point**

Load line is the loading of the transistor seen from Uce (>0V7) Vcc and Rc determines the; “open voltage” and the “short circuit current” Bollen

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**BJT, base bias load line Reliable circuit = Q-point stability**

Load line is the loading of the transistor seen from Uce (>0V7) Vcc and Rc determines the; “open voltage” and the “short circuit current” Bollen

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**BJT, base bias load line Vce always > 0V7 BC junction REVERSE**

If Rc too big, transistor in saturation; then; Bollen

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**BJT, base bias load line Vce always > 0V7 BC junction REVERSE**

If Vcc too small, transistor in saturation; then; Bollen

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**BJT, base bias example Calculate; Ib, Ic URc, Uc, Uce**

Draw output caracteristic Calculate now; Uce if ß = 40 How many % did Uce Change Ib = 47 uA, Ic = 2,35 mA, URc = 5,17 V, Uc = 6,83 V, Uce = 6,83 V Uce (for ß = 40) = 7,86 Ξ 15 % Bollen

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**BJT, base bias example Ib = 33 uA, Ic = 2,9 mA URc = 7,9 V, Uc = 8,1 V**

Rb = 282,5 kΩ, Ic = 3,2 mA, Rc = 1,855 kΩ Bollen

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**BJT, base bias example ß = 200, VRc = 8,8 V Vcc = 16 VRb = 765 kΩ**

Bollen

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**BJT, base bias + emitter feedback**

Base current determined by Vcc, Rb, Vbe and Ve More stable for ß variations, than base bias. Bollen

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**BJT, base bias + emitter feedback**

Always calculate in the smallest current Ib !! Bollen

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**BJT, base bias + emitter feedback**

Load line is the loading of the transistor seen from Uce (>0V7) Vcc, Rc and Re determines the; “open voltage” and the “short circuit current” Bollen

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**BJT, base bias + emitter feedback example**

Calculate; Ib, Ic URc, Uc, Ue, Uce Draw output caracteristic Ib = 6,2 uA, Ic = 0,74 mA, URc = 8,9 V, Uc = 7,1 V, Ue =-0,9 V, Uce = 8,0 V Bollen

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**BJT, base bias + emitter feedback example**

Calculate; Ib, Ie URe, Ue, Uce Draw output caracteristic Ib = 24 uA, Ie = 2,9 mA, URc = 3,5 V, Ue = -2,5 V, Uce = 2,5 V Bollen

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**BJT, base bias + collector/emitter feedback**

If Ic > then Uc < then Ib < If Ic > then Uc < and Ue > then Ib < Bollen

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**BJT, base bias + collector feedback**

Always calculate in the smallest current Ib !! The current through Rc is not Ic but Ic + Ib, so (β+1)Ib !!! If Ic rises for any reason, then Uc falls and also Ib decreases, so then Ic decreases Bollen

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**BJT, base bias collector feedback example**

Calculate; Ib, ß, Ic Draw output caracteristic Ib = 13 uA, ß = 196, Ic = 2,5 mA Bollen

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**BJT, base bias collector/emitter feedback**

Always calculate in the smallest current Ib !! Bollen

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**BJT, base bias collector/emitter feedback ex**

Calculate; Ib, Ie URc, Uc, Ue, Uce Draw output caracteristic Ib = 11,8 uA, Ie = 1,1 mA URc = 5,2 V, Uc = 4,8 V Ue = 1,3 V, Uce = 3,5 V Bollen

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**BJT, voltage divider Vb is a stable voltage - 0,7 V =**

so Ve is a stable voltage Ie is determined by Ve/ Re Ic = Ie . ß/(ß+1) Ic is very stable and nearly independent to ß variation, as long as ß is BIG in value 2 methods of calculating Ic - neglegting Ib, use voltage divider - not neglecting Ib and use thevenin Bollen

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**BJT, voltage divider, neglect Ib**

So neglegt Ib to R2, or in general Ri >> R2 In practice 10 times bigger Bollen

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**BJT, voltage divider, exact, thevenin**

Thevenin resistance R1 // R2 62k // 9k1= 7k9 Thevenin voltage Bollen

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**BJT, voltage divider, exact, thevenin**

7k9 2V0 Ib = 20 uA Bollen

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**BJT, voltage divider, example**

Thevenin resistance = 6k8 Thevenin voltage = 3V1 Ib = 18,8 uA Ic = 2,25 mA re = 11,5 Ω URc = 7V4 Uc = 10V6 Ue = 2V3 Uce = 5V1 Bollen

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**BJT, voltage divider, example**

Thevenin resistance = 255k Thevenin voltage = 0V0 Ib = 14,3 uA Ic = 1,9 mA re = 14 Ω URc = 17V3 Uc = 0V7 Ue = -3V7 Uce = 4V4 Bollen

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BJT Bollen

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BJT Bollen

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