Friday, November 14, 2014

100W AUDIO AMPLIFIER USING TDA7294

TDA7294 is an integrated, monolithic, Class AB audio amplifier designed specifically for Hi-Fi applications. The IC has a DMOS output stage and can deliver 100W RMS into an 8Ohm speaker at +/-38V dual supply. The TDA7294 has low noise, low distortion, good ripple rejection and can be operated from a wide range of supply voltages. The IC has built in short circuit protection and thermal shutdown circuitries. The IC is available in multiwatt 15V and multiwatt 15H packages.

Description


In the circuit TDA7294 is configured to provide 100W output power into an 8Ohm loudspeaker at +/- 38V supply. C8 is the input coupling capacitor and the input is applied to the non-inverting input (Pin3) of the IC. C3 and C9 are power supply filter capacitors while C10 and C4 are bypass capacitors. C2 is the bootstrap capacitor. RC network comprising of R1 and C1 improves the high frequency stability of the amplifier and also prevents oscillations. R2 and C6 sets the mute time constant while R3 and C5 sets the standby time constant. S1 and the mute switch and S2 are the standby switch. R5 is the input resistance and the amplifiers input impedance has a direct relationship to its value. R4 and R6 is used for setting type closed loop gain and with the used value, gain is 30dB. C2 is a feedback capacitor and it also provides DC decoupling.

Circuit Diagram



Notes

  • The supply voltage range is +/- 10V to =/-40V DC.
  • Heat sink is required and its thermal resistance should be around 0.038 degree Celsius/Watt.
  • Use an 8 Ohm 150W speaker as the load.
  • For 100W output the supply voltage must be +/-38VDC.
  • The power supply must be well filtered and free of ripples.
  • If ripples are present in the power supply it may cause oscillations.
  • VM = 1.5V is the mute ON threshold and VM=3.5V is the mute OFF threshold.
  • VSTBY = 1.5V is the standby on threshold and VSTBY = 3.5V is the standby OFF threshold.
  • Typical input resistance of TDA7294 is 100KiloOhm.
  • Frequency response is 20Hz to 20KHz.
  • 145 degree Celsius is the threshold for thermal shutdown. Slew rate of TDA7294 is 10V/microsecond and the open loop voltage gain is 80 dB.
  • Quiescent current of TDA7294 is approximately 30mA and its maximum value is 65mA.
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