Fundamentals of Analog Power AmplifiersLaajuus (3 ECTS)

Objective

Knowledge and understanding:

Learning the important properties of analog power amplifiers and the different design architectures which improve these properties, compared to small-signal amplifiers.

Understanding the trade-offs involved in the circuit design and acquiring insight into the details of operation.

Skills:

Simulation of power amplifiers and assessing efficiency and distortion parameters. Theoretical analysis of these properties.

Content

Introduction

Properties of power amplifiers
- Gain, bandwidth, input- and output impedance
- Maximum voltage and current swing
- Saturation and clipping
- Harmonic distortion
- Power efficiency
- Noise behavior

Class A amplifiers
- Theoretical maximum efficiency derivation
* With resistive load
* With output transformer
- Class A example simulation

Class B amplifiers
- Derivation of theoretical maximum efficiency with resistive load
- Cross-over distortion
- Class AB biasing to reduce distortion
- Class B with feedback to reduce distortion
- Stability risks of feedback power amplifiers, gain and phase margin
- Simulation of Class B and AB amplifiers.

Class C amplifiers
- Expected efficiency
- Applications where class C operation is acceptable
- Simulation of an RF amplifier in class C

Class D amplifiers
- Use of power MOSFETs as switches. Properties and limits.
- Extensive overview of the principles of operation of class D amplifiers
* Half bridge and full bridge configuration
* Boost voltage for high-side NMOS
* Pulse width modulation (PWM)
* Power supply pumping effects
* Dead time and its tradeoff with distortion specifications
* Efficiency
* Output filter requirements
* DC offset problems
* Types of distortion
- Overview of industry-standard fully integrated class D amplifier IC’s
- Extensive simulation of full-bridge class D amplifier

Class E amplifiers
- Conditions for class E operation
- Niche applications that allow very high efficiency
- Simulation of a fixed frequency RF amplifier in class E

Class G and H amplifiers
- Architectures with power supply switching or tracking
- Simulation of both types of amplifiers.

Circuits combining different amplifier classes
- Concept of the Doherty amplifier
- Importance of Doherty amplifiers in 5G base stations
- Simulation of a basic Doherty amplifier

Several practical lab demonstrations for different amplifier classes will be included.

Qualifications

Good understanding of electrical circuit theory.

Basic academic knowledge of diodes, OpAmps, bipolar transistors and MOSFETs.

Basic engineering mathematics: complex numbers, algebra. For some parts: limits, derivatives, integrals.