Power Amplifier Design Guidelines

Contents

• Introduction
• Input Stages
  
  • RF Interference Suppression
• Gain Stages (Class-A Amplifier)
  
  • Active Current Source or Bootstrap?
• Output Stages
  • Thermal Stability
  • Output Stage Linearity
  • Bias Servos
  • Output Stage Stability
• Some Notes on Power Supply Design
• Measurements Vs. Subjectivity
  • Valves Vs. Transistors Vs. MOSFETs
  • Slew Rate and Intermodulation
  • Slew Rate Nomograph

Introduction
I am amazed at the number of amplifier designers who have, for one reason or another, failed to take some of the well known basics and pitfalls of amp design into consideration during the design phase. While some of these errors (whether of judgement or through ignorance is uncertain) are of no great consequence, others can lead to the slow but sure or instantaneous destruction of an amplifier's output devices.
When I say "of no great consequence", this is possibly contentious, since a dramatic increase in distortion is hardly that, however in this context it will at least not destroy anything - other than the listener's enjoyment.
Even well known and respected designs can fall foul of some basic errors - this is naturally ignoring the multitude of "off the wall" designs (e.g. Single-ended MOSFETs without feedback (yecch! - 5% distortion, phtooey), transformer-coupled monstrosities, amplifiers so complex and bizarre that they defy logic or description, etc). This is not including valve amps, these are a "special" case and in many areas, such as guitar amps, they remain unsurpassed.
In this article, I have attempted to cover some of the areas which require their own special consideration, and the references quoted at the end are excellent sources of more detailed information on the items where a reference is given...... For all other Information click on above Links...