Datasheet

LM4950
SNAS174E –JULY 2003–REVISED MAY 2013 www.ti.com
Figure 66. Piezo-electric Transducer Capacitance ≤ 200nF
AUDIO POWER AMPLIFIER DESIGN
Audio Amplifier Design: Driving 4W into an 8Ω BTL
The following are the desired operational parameters:
Power Output 4W
RMS
Load Impedance 8Ω
Input Level 0.3V
RMS
(max)
Input Impedance 20kΩ
Bandwidth 50Hz–20kHz ± 0.25dB
The design begins by specifying the minimum supply voltage necessary to obtain the specified output power.
One way to find the minimum supply voltage is to use the Output Power vs Power Supply Voltage curve in
Typical Performance Characteristics section. Another way, using Equation 8, is to calculate the peak output
voltage necessary to achieve the desired output power for a given load impedance. To account for the amplifier's
dropout voltage, two additional voltages, based on the Clipping Dropout Voltage vs Power Supply Voltage in
Typical Performance Characteristics, must be added to the result obtained by Equation 8. The result is
Equation 9.
(8)
V
DD
= V
OUTPEAK
+ V
ODTOP
+ V
ODBOT
(9)
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