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Volume=20 44 =E2=80=93 May 2010
Ultralow Distortion Audio Panpot Amplifier An audio "panpot" circuit, shown in =
Figure 1,=20
continuously varies the position of a monophonic audio =
signal=20
between left and right stereo channels in response to a =
potentiometer =20
setting. Low cost and low distortion are important =
considerations for =20
audio circuits. The AD8273 Although this circuit can be built = discretely,=20 integrating the amplifiers and resistors on a single chip = offers=20 advantages to board designers, including improved specifications, = =20 less PCB area, and lower production cost. Figure 1. Audio = panpot=20 amplifier. In this circuit, the signal is split =
between the=20
two amplifiers, using series 10-k=E2=84=A6 resistors. A =
potentiometer,=20
with a grounded wiper, is inserted between the two =
noninverting=20
inputs. The combination of the potentiometer and the 10 =
k=E2=84=A6=20
resistors presents a light load that can be easily driven =
by most=20
sources. The amplifiers are configured for a gain of 3. =
When the=20
potentiometer wiper is at either end, one input is =
grounded, so no=20
signal gets through to the corresponding output. The other =
input=20
sees VIN/2, so its =
output is 1.5 =C3=97=20
VIN. With the =
wiper in the=20
middle, the input to both amplifiers is V Figure 2. Total = harmonic=20 distortion and noise vs. frequency. Figure 2 shows the total harmonic = distortion and=20 noise over the audio frequency range. The error increases = with=20 frequency, but the total error is still less than 0.0007% = at 20=20 kHz. Figure 3 shows the connections to the IC. Figure 3. Connection = diagram. References
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