AS1710 datasheet(10/17 Pages) AMSCO

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AS1710/AS1712

Data Sheet - A p p l i c a t i o n I n f o r m a t i o n

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

πRINCIN)(EQ 4)

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

put 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

πRLOADCOUT)(EQ 5)

For a 32

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

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 typi-

cally less than (VDD - 1.2V).

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 fol-

lower. The maximum output voltage swing is load dependent although it is guaranteed to be within 500mV of the posi-

tive rail (VDD = 2.7V) even with maximum load (32

Ω to ground).

VBIAS

RIN

Headphone Jack

to 32

Ω Stereo

Headset

CIN

–

AS1710

RIN

CIN

–

AS1710

COUT

Audio In

Left

Audio In

Right

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