bipolar junction transistor -...

Module: Electronics I Module Number: 610/650221-222 Electronic Devices and Circuit Theory, 9th ed., Boylestad and Nashelsky

Lecturer: Dr. Omar Daoud Part II

Philadelphia University

Faculty of Engineering Communication and Electronics Engineering

Bipolar Junction Transistor

Configurations:

Common Base Configuration

Fig. 3.2 Types of transistors: (a) pnp; (b) npn.

Fig. 3.6 Notation and symbols used with the common-base configuration: npn transistor.

Fig. 3.8 Output or collector characteristics for a common-base transistor amplifier.



Common Emitter Configuration

Common Collector Configuration

Fig. 3.13 Notation and symbols used with the common-emitter configuration: npn transistor

Fig. 3.14 Characteristics of a silicon transistor in the common-emitter configuration: (a) collector characteristics; (b) base characteristics.

Fig. 3.20 Notation and symbols used with the common-collector configuration: (a) pnp transistor; (b) npn transistor.



Operating Point

Fixed Bias Circuit

Fig. 4.1 Various operating points within the limits of operation of a transistor.

Fig. 4.2 Fixed-bias circuit.

Fig. 4.3 DC equivalent of Fig. 4.2.



Fig. 4.4 Base–emitter loop.

Fig. 4.5 Collector–emitter loop.

Fig. 4.7 DC fixed-bias circuit for Example 4.1.

Fig. 4.9 Determining ICsat. Fig. 4.10 Determining ICsat for the fixed-bias configuration.



Emitter Bias

Fig. 4.17 BJT bias circuit with emitter resistor.

Fig. 4.18 Base–emitter loop.

Fig. 4.19 Network derived from the result of Fig. 4.18

Fig. 4.20 Reflected impedance level of RE.

Fig. 4.21 Collector–emitter loop.



Emitter Bias

Fig. 4.14 Effect of an increasing level of RC on the load line

and the Q-point.

Fig. 4.15 Effect of lower values of VCC on the load line and the Q-point.



Design Operation

Transistor Switching Network

Fig. 4.48 Example 4.19.


Fig. 4.53 Transistor inverter.

Saturation conditions and the resulting terminal resistance.

Cutoff conditions and the

resulting terminal resistance.



Fig. 4.56 Inverter for Example 4.24.

Fig. 4.57 Defining the time intervals of a pulse waveform.



Philadelphia University Faculty of Engineering

Communication and Electronics Engineering


AC Analysis: • A model is an equivalent circuit that represents the AC characteristics of the

transistor. • A model uses circuit elements that approximate the behavior of the transistor. • There are two models commonly used in small signal AC analysis of a

transistor: – re model – Hybrid equivalent model

The re Transistor Model:

BJTs are basically current-controlled devices, therefore the re model uses a diode and a current source to duplicate the behavior of the transistor. One disadvantage to this model is its sensitivity to the DC level. This model is designed for specific circuit conditions.

Common Base Configuration

Fig. 5.6 (a) Common-base BJT transistor; (b) re model for the configuration of (a).

Fig. 5.7 Common-base re equivalent circuit.

Fig. 5.9 Defining Av = Vo/Vi for the common-base configuration.



Common Emitter Configuration

Common Collector Configuration Use the common-emitter model for the common-collector configuration.

Fig. 5.11 (a) Common-emitter BJT transistor; (b) approximate model for the configuration of a).

Fig. 5.17 re model for the common-emitter transistor configuration.

Fig. 5.12 Determining Zi using the approximate

Fig. 5.16 Determining the voltage and current gain for the common-emitter transistor amplifier.



The Hybrid Equivalent Model: The following hybrid parameters are developed and used for modeling the transistor. These parameters can be found in a specification sheet for a transistor:

• hi = input resistance • hr = reverse transfer voltage ratio (Vi/Vo) ≅ 0 • hf = forward transfer current ratio (Io/Ii) • ho = output conductance ≅ ∞

Fig. 5.22 Complete hybrid equivalent circuit.

Fig. 5.23 Common-emitter configuration: (a) graphical symbol; (b) hybrid equivalent circuit

Fig. 5.24 Common-base configuration: (a) graphical symbol; (b) hybrid equivalent circuit.



Common-Emitter re vs. h-Parameter Model

Fig. 5.25 Effect of removing hre and hoe from the hybird equivalent circuit.

Fig. 5.26 Approximate hybrid equivalent model.

Fig. 5.27 Hybrid versus re model: (a) common-emitter configuration; (b) common-base configuration.



Philadelphia University

Faculty of Engineering Communication and Electronics Engineering


BJT Amplifier Circuits:

Common Emitter Configurations:

Common Emitter Fixed-bias • The input is applied to the base • The output is from the collector • High input impedance • Low output impedance • High voltage and current gain • Phase shift between input and output is 180°

Fig. 5.34 Common-emitter fixed-bias configuration.

Fig. 5.35 Network of Fig. 5.34 following the removal of the effects of VCC, C1 and C2.

Fig. 5.36 Substituting the re model into the network of Fig. 5.35.

Fig. 5.37Determining Zo for the network of Fig. 5.36.

Co 10Rre

Cv

e

oC

i

ov

r

RA

r)r||(R

VV

A

≥−=

−==

eBCo r10R ,10Rri

eBCo

oB

i

oi

A

)r)(RR(rrR

II

A

ββ

ββ

≥≥≅

++==

C

ivi R

ZAA −=



Common Emitter Voltage-divider Bias


Fig. 5.40 Voltage-divider bias configuration.

Fig. 5.41Substituting the re equivalent circuit into the ac equivalent network of Fig. 5.40.

eCo

Co

r10R ,10Rri

oi

10Rrei

oi

eCo

o

i

oi

II

A

rRR

II

A

)rR)(R(rrR

II

A

ββ

ββ

ββ

≥′≥

≥

≅=

+′′

≅=

+′+′

==

C

ivi R

ZAA −=

Co 10Rre

C

i

ov

e

oC

i

ov

rR

VV

A

rr||R

VV

A

≥−≅=

−==

Fig. 5.38 Demonstrating the 180° phase shift between input and output waveforms.




Common Emitter Bias

Fig. 5.43 CE emitter-bias configuration.




Common Base Configuration • The input is applied to the emitter. • The output is taken from the collector. • Low input impedance. • High output impedance. • Current gain less than unity. • Very high voltage gain. • No phase shift between input and output.

Fig. 5.44 Substituting the re equivalent circuit into the ac equivalent network of Fig. 5.43.

Eb

Eeb

RZE

C

i

ov

)R(rZEe

C

i

ov

b

C

i

ov

RR

VV

A

RrR

VV

A

ZR

VV

A

β

β

β

≅

+=

−≅=

+−==

−==

bB

B

i

oi ZR

RII

A+

==β

C

ivi R

ZAA −=




Fig. 5.57 Common-base configuration.

Fig. 5.58 Substituting the re equivalent circuit into the ac equivalent network of Fig. 5.57.

e

C

e

C

i

ov r

RrR

VV

A ≅==α

1II

Ai

oi −≅−== α


bipolar junction transistor -...

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