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AS1710/AS1712

Datasheet - Application In form atio n

8.2 60mW Single-Supply Stereo Headphone Driver

Two AS1710 amplifiers can be used as a single-supply, stereo headphone driver. The circuit shown in Figure 22 can deliver 60mW per channel

with 1% distortion from a single 5V supply.

Figure 22. Stereo Headphone Driver Application (with Coupling Capacitor)

In Figure 22, CIN and RIN form a high-pass filter that removes the DC bias from the incoming signal. The -3dB point of the high-pass filter is

given by:

f-3dB = 1/(2

RINCIN)(EQ 4)

Choose gain-setting resistors RIN and RF according to the amount of desired gain, keeping in mind the maximum output amplitude.

COUT blocks the DC component of the amplifier output, preventing DC current flowing to the load. The output capacitor and the load impedance

form a high-pass filter with the -3dB point determined by:

f-3dB = 1/(2

RLOADCOUT)(EQ 5)

For a 32

 load, a 100µF aluminum electrolytic capacitor gives a low-frequency pole at 50Hz.

8.3 Rail-to-Rail Input Stage

The AS1710/AS1712 CMOS op-amps have parallel connected N- and P-channel differential input stages that combine to accept a common-

mode range extending to both supply rails. The N-channel stage is active for common-mode input voltages typically greater than (VSS + 1.2V),

and the p-channel stage is active for common-mode input voltages typically less than (VDD - 1.2V).

8.4 Rail-to-Rail Output Stage

The minimum output is within millivolts of ground for single- supply operation, where the load is referenced to ground (VSS). Figure 23 shows the

input voltage range and the output voltage swing of an AS1710 connected as a voltage follower. The maximum output voltage swing is load

dependent although it is guaranteed to be within 500mV of the positive rail (VDD = 2.7V) even with maximum load (32

 to ground).

VBIAS

RIN

Headphone Jack to

32

 Stereo Headset

CIN

+

–

AS1710

RF

RIN

CIN

RF

+

–

AS1710

COUT

+

COUT

+

Audio In

Left

Audio In

Right