1. A.1 Large Signal Operation-Transfer Charact.
Figure 6.32 Biasing the BJT amplifier at a point Q located on the active-mode segment of the VTC.
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2. A.1 Large Signal Operation-Transfer Charact.
sedr42021_0526a.jpg

3. A.2 Amplifier Gain
BJT is biased at a point in active region called Quiescent point

4. A.3 Graphical Analysis
sedr42021_0527.jpg

5. A.3 Graphical Analysis IB must be defined previously.
Q is quiescent bias point
sedr42021_0529.jpg

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7. A.3 Graphical Analysis Small signal analysis around the bias Q point
sedr42021_0530a.jpg

8. A.3 Operation as a Switch Utilize the cutoff and saturation modes.
Edge of saturation (EOS)
sedr42021_0532.jpg

9. A.4 Small Signal Operation and Models
DC bias conditions are set by these equations.
sedr42021_0548a.jpg

10. A.4.1 collector current and transconductance
Small signal approximation
Small signal component or
where or
gm is called transconductance !

11. A.4.1 collector current and transconductance
sedr42021_0549.jpg
Small signal approximation is restricted to an almost linear segment of i-v curve.

12. A.4.2 base current and input resistance at baseor
Small signal r is defined for small signal ib
Therefore, or
is called small signal base resistance

13. A.4.3 emitter current and input resistance
For small signal vbe
Small signal reis defined for small signal ie
Therefore,
is called small signal emitter resistance
r and re relationship

14. Figure 6.38 Illustrating the definition of rπ and re.
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15. Figure 6. 39 The amplifier circuit of Fig. 6
Figure 6.39 The amplifier circuit of Fig. 6.36(a) with the dc sources (VBE and VCC) eliminated (short-circuited). Thus only the signal components are present. Note that this is a representation of the signal operation of the BJT and not an actual amplifier circuit.
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16. A.4.4 Voltage Gain Voltage gain of amplifier is or
Voltage gain is directly proportional to collector current Ic.

17. A.4.5 Separating Signal and DC quantities
Voltage and current are composed of DC and signal components.
since ideal dc supply voltage does not change, the signal voltage across it will be zero.
Amplifier circuit with DC sources
Eliminated (short circuited)
=> We will make equivalent small signal circuit using equivalent small signal
transistor model
sedr42021_0550.jpg

18. A.4.6 The Hybrid- Model the equivalent small signal circuit model
sedr42021_0551a.jpg

19. A.4.7 The T Model
sedr42021_0552a.jpg

20. A.4.8 Application of small signal equivalent circuits
1. Determine DC operating point of BJT (particularly Ic)
2. Calculate values of small signal model parameters such as
gm = Ic/VT, r = /gm, and re = VT/IE.
3. eliminate DC sources by replacing DC voltage with short circuit and DC current with open circuit.
4. Replace BJT with one of small signal equivalent circuit models.
5. Analyze the resulting circuit !
sedr42021_0551a.jpg

21. A.4.8 Application of small signal equivalent circuits
DC operating point
Small signal model parameters
 - model used !
sedr42021_0553a.jpg

22. A.4.8 Application of small signal equivalent circuits

23. A.4.8 Application of small signal equivalent circuits
DC operating point
Small signal model parameters
sedr42021_0555a.jpg

24. A.4.10 Small signal model to account for Early effect.
In most cases, since ro >> RC, reduction in gain is not critical.
Furthermore, we can neglect ro in our analysis for simplifying the circuit analysis.
sedr42021_0558a.jpg

25. A.4.10 Small signal model to account for Early effect.
sedr42021_tb0504a.jpg

26. A.5 Single Stage BJT Amplifier

27. A.5 Single Stage BJT Amplifier
sedr42021_tb0505a.jpg
Table 5.5

28. A.5.1 The common emitter (CE) amplifier
- AC ground at emitter
- CE is bypass capacitor
- CC1 is coupling capacitor
sedr42021_0560a.jpg
Small signal model for circuit

29. A.5.2 CE Amplifier with emitter resistance
Small signal model for circuit
and
sedr42021_0561a.jpg
- It says that input resistance looking into base is +1 times total resistance in emitter (resistance reflection rule)

30. A.5.2 CE Amplifier with emitter resistance
Inclusion of RE in emitter can substantially increase the input resistance.
Therefore, designer can control Rin by controlling value of RE.
Now we determine the voltage gain
 ~ 1
and
voltage gain from base to collector is equal to ratio of collector resistance to emitter resistance.

31. A.5.2 CE Amplifier with emitter resistance
Avo can be expressed in other form.
There is trade between increase in input resistance and decrease in
voltage gain by factor of 1+gmRe
Output resistance :
and
if RB >> Rib
Rib=(+1)(re+Re)

32. A.5.2 CE Amplifier with emitter resistance
Summary of CE amplifier with emitter resistance
- Input resistance is increased by factor of 1+gmRe.
- The voltage gain from base to collector is reduced by factor of 1+gmRe.
- For the same nonlinear distortion, input signal can be increased by factor of 1+gmRe.
- The overall voltage gain is less dependant on .
- The high frequency response is significantly improved.

33. A.5.3 The Common Base (CB) Amplifier
Small signal model for circuit
sedr42021_0562a.jpg
and

34. A.5.3 The Common Base (CB) Amplifier
Summary of CB amplifier with emitter resistance
- Input resistance is very low (re).
- Short circuit current gain is nearly unity ().
- Like CE amplifier, it has high output resistance RC.
- A very importance application of CB amplifier is current buffer.

35. A.5.4 The Common Collector (CC) Amplifier
CC amplifier is commonly used and known by name of emitter follower.
Redrawn for rO parallel with RL.
sedr42021_0563a.jpg
Unlike CE and CB, CC amp. is not
unilateral because Rin depends on
output RL !

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37. Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Figure 5.2 The enhancement-type NMOS transistor with a positive voltage applied to the gate. An n channel is induced at the top of the substrate beneath the gate.
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41. Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Microelectronic Circuits, Sixth Edition
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42. Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Microelectronic Circuits, Sixth Edition
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43. Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Microelectronic Circuits, Sixth Edition
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44. Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Microelectronic Circuits, Sixth Edition
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45. Figure 5. 10 Cross-section of a CMOS integrated circuit
Figure 5.10 Cross-section of a CMOS integrated circuit. Note that the PMOS transistor is formed in a separate n-type region, known as an n well. Another arrangement is also possible in which an n-type body is used and the n device is formed in a p well. Not shown are the connections made to the p-type body and to the n well; the latter functions as the body terminal for the p-channel device.
Microelectronic Circuits, Sixth Edition
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46. Microelectronic Circuits, Sixth Edition
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47. Microelectronic Circuits, Sixth Edition
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48. Microelectronic Circuits, Sixth Edition
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49. Figure 5.20 The relative levels of the terminal voltages of the enhancement-type PMOS transistor for operation in the triode region and in the saturation region.
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50. Microelectronic Circuits, Sixth Edition
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51. Figure 5.28 Biasing the MOSFET amplifier at a point Q located on the segment AB of the VTC.
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54. Figure 5.31 Graphical construction to determine the voltage transfer characteristic of the amplifier in Fig. 5.29(a).
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55. Figure 5. 33 Two load lines and corresponding bias points
Figure 5.33 Two load lines and corresponding bias points. Bias point Q1 does not leave sufficient room for positive signal swing at the drain (too close to VDD). Bias point Q2 is too close to the boundary of the triode region and might not allow for sufficient negative signal swing.
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56. Figure 5.43 The three basic MOSFET amplifier configurations.
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58. Figure 5.49 Illustrating the need for a unity-gain buffer amplifier.
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59. Figure 5.57 (a) Common-source amplifier based on the circuit of Fig (b) Equivalent circuit of the amplifier for small-signal analysis.
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