AD824
3 V, SINGLE SUPPLY STEREO HEADPHONE DRIVER
The
exhibits good current drive and THD + N
performance, even at 3 V single supplies. At 1 kHz, total
harmonic distortion plus noise (THD + N) equals −62 dB
(0.079%) for a 300 mV p-p output signal. This is comparable
to other single supply op amps that consume more power and
cannot run on 3 V power supplies.
In Figure 35, each channel’s input signal is coupled via a 1 µF
Mylar capacitor. Resistor dividers set the dc voltage at the
noninverting inputs so that the output voltage is midway
between the power supplies (1.5 V). The gain is 1.5. Each half of
the
can then be used to drive a headphone channel. A
5 Hz high-pass filter is realized by the 500 µF capacitors and the
headphones, which can be modeled as 32 Ω load resistors to
ground. This ensures that all signals in the audio frequency
range (20 Hz to 20 kHz) are delivered to the headphones.
3V
Data Sheet
LOW DROPOUT BIPOLAR BRIDGE DRIVER
The
can be used for driving a 350 Ω Wheatstone bridge.
being used to buffer the
1.235 V low power reference. The output of 4.5 V
can be used to drive an ADC front end. The other half of the
is configured as a unity-gain inverter and generates the
other bridge input of –4.5 V. Resistors R1 and R2 provide a
constant current for bridge excitation. The
low power
instrumentation amplifier is used to condition the differential
output voltage of the bridge. The gain of the
is pro-
grammed using an external resistor R
G
and determined by:
G
=
49.4 k
Ω
R
G
+
1
+V
S
49.9kΩ
+1.235V
R1
20Ω
1/4
1µF
MYLAR
CHANNEL 1
95.3kΩ
1/4
47.5kΩ
0.1µF
0.1µF
AD589
AD824
26.4kΩ, 1%
TO ADC
REFERENCE INPUT
+V
S
3
R
G
2
7
AD824
500µF
4.99kΩ
HEADPHONES
32Ω IMPEDANCE
R
4.99kΩ
L
10kΩ
1%
350Ω
350Ω
10kΩ
1%
350Ω
350Ω
95.3kΩ
10kΩ
10kΩ
AD824
5
4
6
10kΩ
1%
1/4
V
REF
–V
S
AD824
–4.5V
R2
20Ω
+V
S
0.1µF
GND
1µF
1µF
+5V
AD824
00875-035
CHANNEL 2
500µF
–V
S
0.1µF
–V
S
–5V
Figure 36. Low Dropout Bipolar Bridge Driver
Figure 35. 3 Volt Single Supply Stereo Headphone Driver
Rev. E | Page 14 of 16
00875-036
1µF
MYLAR
47.5kΩ
1/4
AD [ ANALOG DEVICES ]
