General Description
The LME49600 is a high performance, low distortion high fi-
delity 250mA audio buffer. Whereas there are many uses for
the LME49600, this application note describes a headphone
amplifier circuit and associated demonstration board. De-
signed for use inside an operational amplifier’s feedback loop,
it increases output current, improves capacitive load drive,
and eliminates thermal feedback.
The LME49600 offers a pin-selectable bandwidth: a low cur-
rent, 110MHz bandwidth mode that consumes 8mA and a
wide 180MHz bandwidth mode that consumes 15mA. In both
modes the LME49600 has a nominal 2000V/
μ
s slew rate.
Bandwidth is easily adjusted by either leaving the BW pin un-
connected, connecting a resistor between the BW pin and the
V
EE
pin or connecting the BW pin directly to the V
EE
pin.
The LME49600 is fully protected through internal current limit
and thermal shutdown.
Operating Conditions
■
Temperature Range
–40°C
≤
T
A
≤
85°C
■
Amplifier Power
Supply Voltage
2.5V
≤
V
S
±17V
Board Features
The LME49600/LME49720 Stereo Headphone Amplifier
demonstration board has all of the necessary connections,
using RCA jacks, 1/8” stereo headphone jack and 0.100”
headers, to apply the power supply voltage and the audio in-
put signals. The amplified audio signal is available on both a
stereo headphone jack and auxiliary output connections.
Also present on the demonstration board is a potentiometer
to control the stereo output signal magnitude.
Schematic
Figure 2 shows the LME49600/LME49720 Stereo Head-
phone Amplifier Demonstration Board schematic. Refer to
Table 3 for a list of the connections and their functions.
30047317
Figure 2. The LME49600 Demonstration Board Schematic
Note: The LM4562, LME49720, or LME49860 can be used.
www.national.com
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AN-1768
