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AS1701, AS1706

8 Detailed Description

The AS1701/AS1706 bridged audio power-amplifiers can deliver 1.6W into 4

Ω while operating from a single 2.7 to

5.5V supply. The devices consist of two high-output-current operational amplifiers configured as a bridge-tied load

(BTL) amplifier as shown in Figure 29.

Figure 29. AS1701 Typical Configuration Block Diagram

The gain of the devices is set by the closed-loop gain of the input operational amplifier. As shown in Figure 29, the out-

put of the first amplifier serves as the input to the second amplifier, which is configured as an inverting unity-gain fol-

lower in both devices. This results in two outputs, identical in magnitude, and 180° out-of-phase.

Bias

The devices operate from a single 2.7 to 5.5V supply and contain an internally generated, common-mode bias voltage

of:

(EQ 1)

referenced to ground. Bias provides click-and-pop suppression and sets the DC bias level for the audio outputs. For

nally connected to the non-inverting input of one amplifier, and should be connected to the non-inverting input of the

other amplifier for proper signal biasing (see Figure 29).

Shutdown

The integrated 100nA, low-power shutdown circuitry reduces quiescent current consumption. As shutdown com-

mences, the bias circuitry is automatically disabled, the device outputs go high impedance, and bias is driven to GND.

Note:

Current Limit

The AS1701/AS1706 current limit circuitry protects the device during output short-circuit and overload conditions.

enters a pulsing mode, reducing the average output current to a safe level. The amplifier remains in this mode until the

short-circuit or overload condition is corrected.

40k

Ω

4 or 8

Ω

40k

Ω

50k

Ω

50k

Ω

Bias

20k

Ω

20k

+

–

+

–

0.33µF

Audio

Input

0.1µF

Av = -1

0.1 to

1.0µF

+

+

AS1701

IN-

IN+

BIAS

SHDN

GND

OUT-

OUT+