microwave amplifier design - kntu · microsoft powerpoint - slide6.pptx author: dr shamsi created...
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Microwave Amplifier Design
1
Microwave Amplifier Diagram
2
Gain Definitions
3
Cont’d
4
After a few manipulations, we have:
Source Mismatch Factor
5
P
T
AVS
ins G
GPP
M
Load Mismatch Factor
6
A
T
AVN
LL G
GPPM
Example#1
7
Cont’d
8
Cont’d
9
Stability Consideration
10
Cont’d
11
Stability Circle in the Smith Chart
12
Stable and Unstable Regions in ΓL Plane
13
Stable and Unstable Regions in Γs Plane
14
Conditions for Unconditional Stability
15
Example#2
16
For f=500 MHz, we have:
For f=1 GHz, we have:
Cont’d
17
Γs Plane
Cont’d
18
ΓL Plane
Stability Consideration
19
A straightforward but somewhat lengthy manipulations result in the following necessary and sufficient conditions for unconditional stability:
Stern’s stability factor:
Example#3
20
Cont’d
21
Example#4
22
Cont’d
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Cont’d
24
Improving Stability
25
Unilateral Transistor: S12=0
26
In a unilateral case we have:
Cont’d
27
Maximum Achievable Gain(Unilateral Case: S12=0)
28
Bilateral Transistor(S12≠0)
29
Solving above equations, Γs and ΓL are obtained:
It is proven maximum gain is obtained when simultaneous conjugate match exists.
Maximum Achievable Gain (Bilateral Case: S12≠0)
30
It is proven that:
The maximum stable gain is defined as the value of GTmax when K=1. Namely,
Example
31
BJT Bias Network
32
BJT Bias Network
33
GaAs FET Bias Network
34
GaAs FET Bias Network
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GaAs FET Bias Network
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GaAs FET Bias Network
37