In Figure 23, Figure 24 the performances of the system in terms of distortion and output power at various

frequencies (measured on PCB shown in Figure 21) are displayed.

The output power that the TDA7294 in highefficiency application is able to supply at Vs = + 40 V / + 20 V / - 20 V /

- 40 V; f = 1 kHz is:

- Pout = 150 W @ T.H.D. = 10 % with Rl = 4 Ω

- Pout = 120 W @ T.H.D. = 1 % with Rl = 4 Ω

- Pout = 100 W @ T.H.D. = 10 % with Rl = 8 Ω

- Pout = 80 W @ T.H.D. = 10 % with Rl = 8 Ω

Results from efficiency measurements (4 and 8 Ω loads, Vs = ± 40 V) are shown by figures Figure 25 and

Figure 26. We have 3 curves: total power dissipation, power dissipation of the TDA7294 and power dissipation of

the darlingtons.

By considering again a maximum average output power (music signal) of 20 W, in case of the high efficiency

application, the thermal resistance value needed from the heatsink is 2.2 °C / W (Vs = ± 40 V and Rl = 4 Ω).

All components (TDA7294 and power transistors T1 and T2) can be placed on a 1.5 °C / W heatsink, with the

power darlingtons electrically insulated from the heatsink.

Since the total power dissipation is less than that of a usual class AB amplifier, additional cost savings can be

obtained while optimizing the power supply, even with a high headroom.

TDA7294

Application information

DS0013 - Rev 8

page 19/31