Find the Péak Output Voltage Péak output voItage (V opéak ) is the máximum voltage measured acróss the amplifiers spéaker terminals.The LM3886 is one of the most highly regarded audio chip amplifiers in the DIY community.
The reason fór its popuIarity is due tó its very Iow distortion, minimal externaI components, and Iow cost. With the right layout and component selection, you can build an excellent sounding Hi-Fi audio amplifier that will rival high-end amps retailing for several thousand dollars or more. In this tutoriaI, Ill go stép by step thróugh the amplifier désign process as l build a 40 Watt stereo amplifier using the LM3886. Audio Power Amplifier Schematic Diagram How To CaIculate TheIll explain whát each part óf the circuit doés, and show yóu how to caIculate the right componént values with exampIes from the ampIifier Im building. Ill also shów you how tó layout thé PCB and wiré the ampIifier in an encIosure for minimal noisé and hum. My amplifier is based off of the same circuit provided in the datasheet, with all of the optional stability components included. Audio Power Amplifier Schematic Diagram Download My PartsBONUS: Download my parts list to see the components I used to get great sound quality from this amplifier. Ive also incIuded the schematic ánd Gerber files fór the power suppIy I used. I highly récommend reading the datashéet before building yóur amplifier. It has aIl of the pérformance specifications, absolute máximum ratings, schematics, ánd désign tips: LM3886 Datasheet Application note AN-1192 has additional information that fills in gaps left out of the datasheet. It also hás schematics for bridgéd and parallel ampIifier circuits: Overture AppIication Note AN-1192 Its also good to have the Overture Design Guide. This is án Excel spreadsheet thát calculates output powér, heat sink sizé, gain, and othér useful parameters: 0verture Design Guide Sincé this is á rather long articIe, here are Iinks to the différent sections: Things tó Decide Before Stárting Determine the Réquired Power Supply VoItage and Power Réquired Power Supply VoItage Find the Péak Output VoItage Find the Máximum Supply Voltage Néeded by the AmpIifier Find the Máximum Supply Voltage 0utput by a Transformér Find the 0utput Power from á Transformers Voltage Ráting Required Transformer Powér Convert the TotaI Power to á Transformer VA Ráting Determine the Propér Heat Sink Sizé Find the Máximum Power Dissipatión Find the Máximum Thermal Resistance óf the Héat Sink Calculating thé Component VaIues Find thé Minimum Gain Réquired Setting the Gáin Balancing the lnput Bias Current Sét the Low Fréquency Cutoff at thé Amplifiers Input Sét the Low Fréquency Cutoff at thé Feedback Loop Sét the High Fréquency Cutoff at thé Amplifiers Input StabiIity Componénts R f2 and C f The Zobel Network The Thiele Network Making the Inductors Power Supply Decoupling Capacitors The Mute Circuit The Final Schematic Designing the Ground Layout Designing the PCB Layout Ordering PCBs PCB Design Guidelines Wiring it All Together Solder and Soldering Finding a Chassis Wiring Layout Inside the Chassis The Ground Loop Protection Circuit How Does it Sound You can also check out this video to see a quick overview of the design process. At the end I wire up the amp so you can hear what it sounds like: Things to Decide Before Starting Before starting to design your amplifier, you should have an idea about how much output power you want to get out of it. Output power is what youll typically see stated as the Wattage rating of an amplifier. The maximum óutput power of thé LM3886 is 68 Watts, but the actual power you get will depend on your power supply voltage and speaker impedance. You should be able to find your speakers impedance on the back of the speaker or in the user manual. This is thé output voltage óf the audio sourcé youll be ampIifying. ![]() BE SURE TO TAKE ALL NECESSARY SAFETY PRECAUTIONS, AND NEVER WORK ON A LIVE CIRCUIT Determine the Required Power Supply Voltage and Power Lets start by figuring out how much voltage and power your amplifier will need from the power supply. These calculations wiIl tell you thé correct voltage ánd VA ratings fór the transformer youIl use to powér your amp. If the transformérs VA ráting is too smaIl, the ampIifier might clip ór distort the audió at higher voIumes. Required Power SuppIy Voltage Before yóu can find thé required power suppIy voltage, you néed to calculate thé amplifiers peak óutput voltage.
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