Posted by Circuits99 on June 2, 2021
18W Audio Power Amplifier Circuit using Transistors is the artlcle explaining 18W Audio Power Amplifier Circuit 18W Audio Power Amplifier Circuit designing an audio amplifier capable of delivering a decent output powe...
18W Audio Power Amplifier Circuit
18W Audio Power Amplifier Circuit designing an audio amplifier capable of delivering a decent output power with a minimum parts count, without sacrificing quality. The Power Amplifier section employs only four transistors and a handful of resistors and capacitors in a shunt feedback configuration but can deliver more than 18W into 8 Ohm with 0.08% THD @ 1KHz at the onset of clipping (0.04% @ 1W – 1KHz and 0.02% @ 1W – 10KHz) and up to 30W into a 4 Ohm load
18W Audio Power Amplifier Circuit
To obtain such a performance and to ensure the overall stability of this very simple circuitry, a suitable regulated dc power supply is mandatory. This is not a snag because it also helps in keeping the noise and hum of the preamp to very low levels and guarantees a predictable output power into different load impedance.
Working of Power Amplifier Circuit
- This circuit Can be directly connected to CD players, tuners, and tape recorders.
- Do not exceed 23 + 23V supply.
- Q3 and Q4 must be mounted on the heatsink.
- D1 must be in thermal contact with Q1.
- Quiescent current (best measured with an Avo-meter in series with Q3 Emitter) is not critical.
- Adjust R3 to read a current between 20 to 30 mA with no input signal.
- To facilitate quiescent current setting add R8 (optional).
- A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of J1, P1, C2, C3 & C4. Connect C6 to the output ground.
- Connect separately the input and output grounds to the power supply ground.
Components for 18W Audio Power Amplifier Circuit
P1_____________22K Log. Potentiometer (Dual-gang for stereo)
R1______________1K 1/4W Resistor
R2______________4K7 1/4W Resistor
R3____________100R 1/4W Resistor
R4______________4K7 1/4W Resistor
R5_____________82K 1/4W Resistor
R6_____________10R 1/2W Resistor
R7_______________R22 4W Resistor (wirewound)
R8______________1K 1/2W Trimmer Cermet (optional)
C1____________470nF 63V Polyester Capacitor
C2,C5_________100µF 3V Tantalum bead Capacitors
C3,C4_________470µF 25V Electrolytic Capacitors
C6____________100nF 63V Polyester Capacitor
D1___________1N4148 75V 150mA Diode
IC1________TLE2141C Low noise, high voltage, high slew-rate Op-amp
Q1____________BC182 50V 100mA NPN Transistor
Q2____________BC212 50V 100mA PNP Transistor
Q3___________TIP42A 60V 6A PNP Transistor
Q4___________TIP41A 60V 6A NPN Transistor
J1______________RCA audio input socket
Power Supply Components
R9______________2K2 1/4W Resistor
C7,C8________4700µF 25V Electrolytic Capacitors
D2_____________100V 4A Diode bridge
D3_____________5mm. Red LED
T1_____________220V Primary, 15 + 15V Secondary, 50VA Mains transformer
PL1____________Male Mains plug
SW1____________SPST Mains switch