LM3886

SNAS091C – MAY 1999 – REVISED MARCH 2013

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(excluding active protection circuitry)

External Components Description

(See Figure 1 and Figure 3)

Components

Functional Description

1.

Acts as a volume control by setting the voltage level allowed to the amplifier's input terminals.

2.

Provides DC voltage biasing for the single supply operation and bias current for the positive input terminal.

3.

Provides bias filtering.

4.

C

Provides AC coupling at the input and output of the amplifier for single supply operation.

5.

Prevents currents from entering the amplifier's non-inverting input which may be passed through to the load upon power-

down of the system due to the low input impedance of the circuitry when the under-voltage circuitry is off. This

phenomenon occurs when the supply voltages are below 1.5V.

6.

(1)

Reduces the gain (bandwidth of the amplifier) at high frequencies to avoid quasi-saturation oscillations of the output

transistor. The capacitor also suppresses external electromagnetic switching noise created from fluorescent lamps.

7.

Ri

8.

Feedback capacitor. Ensures unity gain at DC. Also a low frequency pole (highpass roll-off) at:

9.

Feedback resistance to provide AC Gain in conjunction with Ri.

10.

(1)

frequency pole (lowpass roll-off) exists at:

11.

(1)

12.

Mute resistance set up to allow 0.5 mA to be drawn from pin 8 to turn the muting function off.

Performance Characteristics.

13.

Mute capacitance set up to create a large time constant for turn-on and turn-off muting.

14.

(1)

15.

(1)

16.

Provides high impedance at high frequencies so that R may decouple a highly capacitive load and reduce the Q of the

series resonant circuit due to capacitive load. Also provides a low impedance at low frequencies to short out R and pass

17.

audio signals to the load.

18.

Provides power supply filtering and bypassing.

19.

S1

Mute switch that mutes the music going into the amplifier when opened.

(1)

Optional components dependent upon specific design requirements. Refer to Application Information for more information.

OPTIONAL EXTERNAL COMPONENT INTERACTION

Although the optional external components have specific desired functions that are designed to reduce the

bandwidth and eliminate unwanted high frequency oscillations they may cause certain undesirable effects when

they interact. Interaction may occur for components whose reactances are in close proximity to one another. One

low impedances to certain frequencies which will couple signals from the input to the output. Please take careful

note of basic amplifier component functionality when designing in these components.

The optional external components shown in Figure 3 and described above are applicable in both single and split

voltage supply configurations.

8

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