FET-Based Audio Power Amplifier with 12W Output

Figure 1 

The circuit was intended to create a small power amplifier for audio applications while providing high quality audio with a power output of 12 Watts.

• Power Amplifier – a type of amplifier built and designed for the purpose of delivering and supplying sufficient and maximum high output power to directly drive loudspeakers or loads, within a given percent of distortion
• NE5534 – a high performance low noise operational amplifier having a combined excellent AC and DC characteristics and features such as capability of external compensation, capability of offset nulling, wide range of voltage supply, low harmonic distortion, with output voltage swing at peak to peak, high slew rate, 100 dB common mode rejection ratio, high gain of DC Voltage, unity gain bandwidth at 10 MHz, and noise voltage of equivalent input
• 2SK135 – a Silicon N-Channel MOSFET used for low frequency power amplifier with features such as being equipped with gate protection diodes, good complementary characteristics, enhancement mode, wide area of safe operation, high speed switching, excellent frequency response, and high power gain, and is the complement of 2SJ49
• 2SJ50 – a Silicon P-Channel power MOSFET designed for motor/lamp driver circuits and DC/DC converters with features such as built-in gate protection diode, low current, and low on-state resistance, and is the complementary of 2SK134

The acquisition of the operational amplifier NE5534 provides the circuit the ability to handle and control low loads at high speeds since this specific op-amp possess a very good quality feature with two transistors in the V-MOSFET technology located on its output. The V-MOSFET is a type of power MOSFET used for several applications where the requirements are medium powers and has an arranged structure with a V-groove.

On the other hand, the IC1 can be replaced with other equivalent component suitable for the operation while the supply in the stage of the output is given some increased value. It should be noted that the voltage supply of IC1 should be maintained carefully depending on the level of its specifications. The addition of the Zener diodes provides help in maintaining the required voltage. In this way, the desired increase of the power output will be achieved. The maximum output power that the circuit will provide in an 8 Ohms load is 12 W while the total harmonic distortion (THD) is only at 0.002% for every 1 KHz of frequency. If the circuit will be used for stereo operations or applications, two units should be built to be able to function well.

Figure 2 

The concept of this audio power amplifier with 12 W output is suitable for low loads that would not exceed 8 Ohms of resistance. In the broadcasting industry, it is referred to as the ideal companion of phase-locked loop transmitter and any other 500 mW to 1 W transmitter with tested and fully built heatsink attached.

Source:users.otenet.gr/~athsam/power_amplifier_12w_fet.htm