[Glenn's Audio and Hi-Fi Page] [A25 Amplifier] [A60 Amplifier] [A100 Amplifier]

These equations are presented as a general procedure for the design of the major power supply and current parameters of these Class A power amplifiers. The allowed-for losses are approximate. A reactive "loudspeaker" load and "musical" voltage waveforms will increase the current requirements. sqrt( ) means the square root of whatever is contained within the parentheses.

## Requirements | ## Model A100 |
## Model A60 | ## Model A25 |

Prms (RMS power output, Watts) | 100 W | 60 W | 25 W |

Rl (Resistive load, Ohm) | 8 Ohm | 8 Ohm | 8 Ohm |

## Output Voltage | |||

Erms (RMS output voltage, Volts) = sqrt( Prms Rl ) |
28.3 V | 21.9 V | 14.1 V |

Epeak (Peak output voltage, Volts) = sqrt( 2 ) Erms |
40.0 V | 31.0 V | 20.0 V |

Esupply (Supply voltage, Volts) ~= Epeak x 1.15 to allow for device and resistive drops |
46 V | 36 V | 23 V |

Eac (Power Transformer AC voltage, Volts) |
34 V | 28 V | 18 V |

## Output Stage Current | |||

Irms (RMS current, Amps) = sqrt( Prms / RL ) |
3.5 A | 2.7 A | 1.8 A |

Ipeak (Peak current, Amps) = sqrt( 2 ) Irms |
5 A | 3.9 A | 2.5 A |

Iq (Quiescent current, Amps) |
2.5 A | 1.95 A | 1.25 A |

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© 1999 Glenn Baddeley.

http://home.pacific.net.au/~gnb/audio/adesign.html was last updated 13 December 1999.

Report problems and send comments to Glenn Baddeley.