the voltage applied to the BYPASS pin. The gain of the

internal amplifiers remains unity until the voltage on the

bypass pin reaches 1/2 V

BYPASS pin is stable, the device becomes fully operational.

Although the bypass pin current cannot be modified, chang-

ing the size of C

magnitude of "clicks and pops". Increasing the value of C

B

reduces the magnitude of turn-on pops. However, this pre-

sents a tradeoff: as the size of C

increases. There is a linear relationship between the size of

C

for various values of C

C

B

T

ON

0.01µF

20 ms

0.1µF

200 ms

0.22µF

440 ms

0.47µF

940 ms

1.0µF

2 Sec

In order eliminate "clicks and pops", all capacitors must be

discharged before turn-on. Rapidly switching V

allow the capacitors to fully discharge, which may cause

"clicks and pops".

NO LOAD STABILITY

The LM4816 may exhibit low level oscillation when the load

resistance is greater than 10k

Ω. This oscillation only occurs

as the output signal swings near the supply voltages. Pre-

vent this oscillation by connecting a 5k

Ω between the output

pins and ground.

AUDIO POWER AMPLIFIER DESIGN

Audio Amplifier Design: Driving 1W into an 8

Ω Load

The following are the desired operational parameters:

Power Output:

1W

RMS

Load Impedance:

8

Ω

Input Level:

1V

RMS

Input Impedance:

20k

Ω

Bandwidth:

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 Supply Voltage curve in the Typical Performance Char-

acteristics section. Another way, using Equation (4), is to

calculate the peak output voltage necessary to achieve the

desired output power for a given load impedance. To ac-

count for the amplifier’s dropout voltage, two additional volt-

ages, based on the Dropout Voltage vs Supply Voltage in the

Typical Performance Characteristics curves, must be

added to the result obtained by Equation (8). The result in

Equation (9).

(8)

V

DD

≥ (V

(9)

The Output Power vs Supply Voltage graph for an 8

Ω load

indicates a minimum supply voltage of 4.6V. This is easily

met by the commonly used 5V supply voltage. The additional

voltage creates the benefit of headroom, allowing the

LM4816 to produce peak output power in excess of 1W

without clipping or other audible distortion. The choice of

supply voltage must also not create a situation that violates

maximum power dissipation as explained above in the

Power Dissipation section.

After satisfying the LM4816’s power dissipation require-

ments, the minimum differential gain is found using Equation

(10).

(10)

Thus, a minimum gain of 2.83 allows the LM4816’s to reach

full output swing and maintain low noise and THD+N perfor-

mance. For this example, let A

The amplifier’s overall gain is set using the input (R

feedback (R

set at 20k

Ω, the feedback resistor is found using Equation

(11).

R

(11)

The value of R

Ω.

The last step in this design example is setting the amplifier’s

pass band magnitude variation limit, the low frequency re-

sponse must extend to at least one−fifth the lower bandwidth

limit and the high frequency response must extend to at least

five times the upper bandwidth limit. The gain variation for

desired limit. The results are an

f

(12)

and an

F

(13)

As mentioned in the External Components section, R

i

and C

bandpass frequency limit. Find the coupling capacitor’s

value using Equation (14).

(14)

the result is

1/(2

π*20kΩ*20Hz) = 0.398µF

(15)

Use a 0.39µF capacitor, the closest standard value.

The product of the desired high frequency cutoff (100kHz in

this example) and the differential gain, A

upper passband response limit. With A

100kHz, the closed-loop gain bandwidth product (GBWP) is

300kHz. This is less than the LM4816’s 3.5MHz GBWP. With

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