This is a 18 Watt audio amplifier circuit based on power IC HA13118. The supply voltage required for this circuit is 8 – 18V DC, at least 1 to 2 Amps. Maximum output power will only be obtained with a power supply of 18V at greater than 2 A, using a 4 ohm speaker. The power supply should be well filtered to reduce mains hum, a regulated supply will reduce noise even further. Extra filtering is unnecessary if operating from a battery supply.
Resistors : R1, R2 ___________________ 2R2 ohm Capacitors : C1, C2, C4, C5, C6 _______ 100uF/16V electrolytic capacitor C3 _______________________ 10uF/16V electrolytic capacitor C7, C8, C12 ______________ 100nF C9 _______________________ 2,200uF/25V electrolytic capacitor C10 ______________________ 1uF/50V electrolytic capacitor C11 ______________________ 100pF Misc. I.C. _____________________ HA13118 Heatsink
C10 is the input coupling capacitor and blocks DC from the input. C11 bypasses any RF which may be present at the input. C1 & C2 provide an AC ground for the inverting inputs of the IC. R1/C7 and R2/C8 provide a high frequency load for stability with difficult speakers. C5 and C6 provide “bootstrap” feedback for the IC. C9 and C12 provide power supply filtering. Don’t forget that heatsink is a must for this class AB power amplifier circuit.
18 Watt Audio Amplifier Specifications :
D.C. Input : 8 – 18V at 1 - 2 A Power output : 18W maximum, 4 ohm load, 18V DC supply > 10W RMS 4 ohm load, 18V DC supply > 5W RMS 8 ohm load 18V DC supply > 6W RMS 4 ohm load 12V DC supply S/N ratio : > 70 dB THD < 0.2% @ 1W Freq. Response : ~ 30 Hz to 30 kHz, –3 dB Input level : < 25 mV, for full output (G > 50dB) Input Impedance ~ 30 k ohm
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