This mini audio amplifier circuit is designed for low power audio amplifier with small dimensions such as CD player, iPod, Walkman, computers and others. The circuit shown here is a single channel, if you want to build it a stereo you just make two exactly the same circuit.
You can see this mini audio amplifier circuit is so simple and easy to build. This circuit is one of a series that fully using transistor, instead of using the IC. One of the advantages that using the transistor, harmonic distortion is relatively lower than the amplifier circuit with IC. Besides audio transistor components more easily obtained.
This amplifier can work well on a 12VDC power supply. Switch SW 1 serves as a bass-boost. But if you want to activate SW1, the volume control should also be increased to reduce power losses at high frequencies.
Some things you should consider in assembling this amplifier circuit is; R9 must be adjusted carefully so that the audio signal on the speaker inaudible distortion. At the time of standby, the current in the collector of Q3 should be at 10-15 mA. This can be done by making measurements using a multimeter.
2 Watt Mini Audio Amplifier based Transistors Components list:
|P1 = 10K||Log.Potentiometer|
|R1,R2 = 33K||1/4W Resistors|
|R3 = 33R||1/4W Resistor|
|R4 = 15K||1/4W Resistor|
|R5,R6 = 1K||1/4W Resistors|
|R7 = 680R||1/4W Resistor|
|R8 = 120R||1/2W Resistor|
|R9 = 100R||1/2W Trimmer Cermet|
|C1,C2 = 10?F||63V Electrolytic Capacitors|
|C3 = 100?F||25V Electrolytic Capacitor|
|C4,C7 = 470?F||25V Electrolytic Capacitors|
|C5 = 47pF||63V Ceramic Capacitor|
|C6 = 220nF||63V Polyester Capacitor|
|C8 = 1000?F||25V Electrolytic Capacitor|
|D1 = 1N4148||75V 150mA Diode|
|Q1 = BC560C||45V 100mA PNP Low noise High gain Transistor|
|Q2 = BC337||45V 800mA NPN Transistor|
|Q3 =TIP31A||60V 4A NPN Transistor|
|Q4 = TIP32A||60V 4A PNP Transistor|
|SPKR||3-5 Watt Loudspeaker, 8, 4 or 2 Ohm impedance|
2 Watt Mini Audio Amplifier based Transistors Specs:
- Output power: 1.5 Watt RMS @ 8 Ohm, 2.5 Watt @ 4 Ohm, 3.5 Watt @ 2 Ohm (1KHz sinewave)
- Sensitivity: 100mV input for 1.5W output @ 8 Ohm
- Frequency response: 30Hz to 20KHz -1dB
- Total harmonic distortion @ 1KHz & 10KHz: Below 0.2% @ 8 Ohm 1W, below 0.3% @ 4 Ohm 2W, below 0.5% @ 2 Ohm 2W.