LM4782TASLASHNOPB datasheet(8/33 Pages) TI1

8 / 33 page

LM4782, LM4782TABD

SNAS231B – FEBRUARY 2004 – REVISED MARCH 2013

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External Components Description

Figure 1, Figure 3, Figure 4, Figure 5, and Figure 6

Components

Functional Description

Prevents current from entering the amplifier's non-inverting input. This current may pass through to the load during

system power down, because of the amplifier's low input impedance when the undervoltage circuitry is off. This

phenomenon occurs when the V+ and V-supply voltages are below 1.5V.

Inverting input resistance. Along with Rf, sets AC gain.

Feedback resistance. Along with Ri, sets AC gain.

Rf2

(1)

Feedback resistance. Works with Cf and Rf creating a lowpass filter that lowers AC gain at high frequencies. The

-3dB point of the pole occurs when: (Rf - Ri)/2 = Rf // [1/(2πfcCf) + Rf2] for the Non-Inverting configuration shown in

Figure 6.

(1)

Compensation capacitor. Works with Rf and Rf2 to reduce AC gain at higher frequencies.

(1)

Compensation capacitor. Reduces the gain at higher frequencies to avoid quasi-saturation oscillations of the output

transistor. Also suppresses external electromagnetic switching noise created from fluorescent lamps.

(1)

Feedback capacitor which ensures unity gain at DC. Along with Ri also creates a highpass filter at fc = 1/(2πRiCi).

Provides power supply filtering and bypassing. Refer to the Supply Bypassing application section for proper

placement and selection of bypass capacitors.

(1)

Acts as a volume control by setting the input voltage level.

RIN

(1)

Sets the amplifier's input terminals DC bias point when CIN is present in the circuit. Also works with CIN to create a

highpass filter at fC = 1/(2πRINCIN). If the value of RIN is too large, oscillations may be observed on the outputs

when the inputs are floating. Recommended values are 10k

Ω to 47kΩ. Refer to Figure 6.

CIN

(1)

Input capacitor. Prevents the input signal's DC offsets from being passed onto the amplifier's inputs.

RSN

(1)

Works with CSN to stabilize the output stage by creating a pole that reduces high frequency instabilities.

CSN

(1)

Works with RSN to stabilize the output stage by creating a pole that reduces high frequency instabilities. The pole is

set at fC = 1/(2πRSNCSN). Refer to Figure 6.

L(1)

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

the series resonant circuit. Also provides a low impedance at low frequencies to short out R and pass audio signals

R(1)

to the load. Refer to Figure 6.

Provides DC voltage biasing for the transistor Q1 in single supply operation.

Provides bias filtering for single supply operation.

RINP

(1)

Limits the voltage difference between the amplifier's inputs for single supply operation. Refer to the CLICKS AND

POPS application section for a more detailed explanation of the function of RINP.

RBI

Provides input bias current for single supply operation. Refer to the CLICKS AND POPS application section for a

more detailed explanation of the function of RBI.

Establishes a fixed DC current for the transistor Q1 in single supply operation. This resistor stabilizes the half-

supply point along with CA.

Limits the current drawn into the logic gates for the MUTE and STANDBY pins.

Standby switch. When switched to GND, the amplifier will be in PLAY mode.

Mute switch. When switched to GND, the amplifier will be in PLAY mode.

ROUT

Reduces current flow between outputs that are caused by Gain or DC offset differences between the amplifiers.

(1)

Optional components dependent upon specific design requirements.

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