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TDA7294-Based Power Amplifier for Audio Circuits
The circuit was designed to produce a power amplifier with the utilization of TDA7294 integrated circuit to drive audio circuits for 60 Watts power.
- 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
- TDA7294 – a monolithic integrated circuit in 15 multi watt packages, intended for use as audio class AB amplifier in Hi-Fi field applications like top-class TV, self-powered speakers, and home stereo due to its short circuit protection, very low noise & distortion, thermal shutdown, muting/standby functions, no switch ON/OFF noise, high power output, no Boucherot cells, DMOS power stage, and very high range of operating voltage
- Class AB Amplifier – functions as a class B amplifier that eliminates virtually all of the crossover distortion by having a small amount of bias current that is constantly flowing through the output transistors
The use of integrated circuit TDA7294 is best suited to function in hi-fi applications as an audio class AB amplifier. The highest power is capable of being supplied into both 4 ohm and 8 ohm loads because the IC has output current capability and wide range voltage. Moreover, an 8 ohm load having 0.1% total harmonic distortion (THD) can be supplied with 50 W RMS, with the addition of sufficient power supply and minimal amount of components. The presence of a heatsink will suppress excess temperature at a rate of 1.4ºC/W. The STANDBY mode is handled by pin 9 while the MUTE input is handled by pin 10. The STANDBY mode is always taking precedence after the MUTE input.
The amplifier is activated immediately during the power up. This is made sure due to the pins being connected permanently to the supply rail. The switch-ON clicks can be eliminated by increasing the time constants of C5 & R4 and C6 & R3. Due to the internal thermal protection of the IC, a temperature at 145ºC can cause the MUTE state while at 150ºC, the amplifier will be at STANDBY mode. The amplifier circuit should not be operated without the presence of the heatsink that is internally attached to the rail of the negative supply. The IC can be insulated from the heatsink it the amplifier is mounted inside an earthed metal enclosure. The maximum voltage supply for 8 ohm load is 40V while 30V for 4 ohm load, with a transformer rated at 80 VA or 150 VA for two modules in a stereo amplifier.
C1=1.5uF 63V MKT Polyester
C2=2.7nF 63V MKT Polyester
C3-4=100nF 100V MKT Polyester
C5-6=10uF 63V Electrolytic
C7=22uF 63V Electrolytic
C8=33uF 25V Electrolytic
C9-10=1000uF 63V Electrolytic
IC1=TDA7294 on Heatsink
J1=2pin connector with 2.54mm step
JP1-2=2pin Jumper with 2.54mm step
All Resistors are 1/4W 1%
All Electrolytic Capacitors are Axial
Class AB amplifiers have been widely and conventionally used in audio industry to drive loudspeakers in audio systems since they are efficient enough to drive at around 100W maximum power output required without releasing excessive heat. It is also denoted as push-pull amplifier that is utilized in commercial operational amplifier as the output stage since they are the most common type of design in audio power amplifiers.