This document provides an overview of low noise, high power, and broadband amplifier design within communication systems, highlighting the importance of effective information transfer. It details the architecture of basic radio systems, particularly the superheterodyne design patented in 1917, along with various circuit techniques for broadband amplifier design. Key considerations for power amplification and matching techniques are also discussed, focusing on achieving optimal output power.

1. Chapter 4-2
Introduction to Low Noise, High Power,
and Broadband Amplifier Design
Chien-Jung Li
Department of Electronics Engineering
National Taipei University of Technology

2. Department of Electronic Engineering, NTUT
Functional Block Diagram of Communication Systems
Input
Transducer
Output
Transducer
Input Signal
(Audio, Video, Data)
Output Signal
(Audio, Video, Data)
Transmitter
(Tx)
Receiver
(Rx)
Channel
• The main job of the communication systems is to transfer
useful information from one end to the other ends.
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3. Department of Electronic Engineering, NTUT
Block Diagram of a Basic Radio System
• Transmitter (Tx)
• Receiver (Rx)
Data in
Modulator IF Filter Mixer
Bandpass Filter
(BPF) Power Amplifier
(PA)
Antenna
Local
Oscillator
(LO)
Bandpass Filter
(BPF) Mixer IF Filter
Data out
DemodulatorIF Amplifier
Local
Oscillator
(LO)
Low Noise
Amplifier
(LNA)
Antenna
 This architecture was first called superheterodyne and patented in 1917 by
Armstrong. The “transceiver” means the system that combines Tx and Rx.
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4. Department of Electronic Engineering, NTUT
Constant NF Circles
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5. Department of Electronic Engineering, NTUT
Noise Circle and Gain Circles (I)
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6. Department of Electronic Engineering, NTUT
Noise Circle and Gain Circles (II)
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7. Department of Electronic Engineering, NTUT
Noise Circle and Gain Circles (III)
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8. Department of Electronic Engineering, NTUT
Broadband Design
• The most popular and well-established circuit techniques
employed in the design of broadband amplifiers that are
generalized in hybrid and monolithic technologies are:
 Reactively matched circuit
 Traveling wave distributed circuit
 Feedback circuit
 Lossy matched circuit
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9. Department of Electronic Engineering, NTUT
Broadband Stability
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10. Department of Electronic Engineering, NTUT
Broadband v.s. Narrowband Matching
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11. Department of Electronic Engineering, NTUT
PA Matching Considerations
• In order to obtain maximum output power, typically the power
amplifier is not conjugately matched. In stead, the load is designed
such that the amplifier has the correct voltage and current to deliver
the required power.
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12. Department of Electronic Engineering, NTUT
Matching to S22* vesus Matching to Γopt
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13. Department of Electronic Engineering, NTUT
Class A, AB, C PAs
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14. Department of Electronic Engineering, NTUT
Power Contour
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15. Department of Electronic Engineering, NTUT
Power Combing
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16. Department of Electronic Engineering, NTUT
Cascaded PA
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