AN2583 datasheet(10/18 Pages) STMICROELECTRONICS

10 / 18 page

Audio characteristics

AN2583

10/18

2.2.3

Getting more power

One technique for increasing the deliverable power is to add a negative supply equal in

magnitude to the positive supply. This is depicted in Figure 10. With this addition, the

midpoint, VX, is at ground. One advantage of this is that no coupling capacitor is required

thus removing any frequency roll off effects due to using an imperfect, real-world capacitor.

Figure 10.

Amplifier with symmetric supplies

Thus, without the capacitor, VL = VX. For this topology, ignoring the VDS drops in Q1 and Q2

as before, VX will swing between VDD and –VDD as shown in Figure 11.

Figure 11.

Output of amplifier with symmetric supplies

As before, the continuous power to the load is

At maximum continuous output power, VL-PK equals VDD, so this becomes

Thus, compared to Equation 1, by adding the negative supply, the maximum power

increased by a factor of 4. The same effect could also be achieved by doubling VDD in the

circuit of Figure 7.

But either way, adding a supply or doubling the voltage can be costly. It is preferred to get

the increase in power without such additional costs.

VDD

VIN

VDSP

–

VDSN

–

VSS = –VDD

GND

ai13936

VDD

VL = VX

VLPP

VL-PK

ai13937

max

AN2583 数据表(PDF) 10 Page - STMicroelectronics

AN2583 数据表(HTML) 10 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

数据表下载