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PDF LM4908 Data sheet ( Hoja de datos )
| Número de pieza | LM4908 | |
| Descripción | 10kV ESD Rated Dual 120 mW Headphone Amplifier | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LM4908 (archivo pdf) en la parte inferior de esta página. Total 21 Páginas | ||
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February 2004
www.DataSheet4U.com
LM4908
10kV ESD Rated, Dual 120 mW Headphone Amplifier
General Description
The LM4908 is a dual audio power amplifier capable of
delivering 120mW per channel of continuous average power
into a 16Ω load with 0.1% (THD+N) from a 5V power supply.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components using surface mount packaging. Since
the LM4908 does not require bootstrap capacitors or snub-
ber networks, it is optimally suited for low-power portable
systems.
The unity-gain stable LM4908 can be configured by external
gain-setting resistors.
Key Specifications
j THD+N at 1kHz at 120mW
continuous average output power
into 16Ω
j THD+N at 1kHz at 75mW
continuous average output power
into 32Ω
0.1% (typ)
0.1% (typ)
j Output power at 0.1% THD+N
at 1kHz into 32Ω
75mW (typ)
Features
n Up to 10kV ESD protection on all pins
n MSOP, SOP, and LLP surface mount packaging
n Switch on/off click suppression
n Excellent power supply ripple rejection
n Unity-gain stable
n Minimum external components
Applications
n Headphone Amplifier
n Personal Computers
n Portable electronic devices
Typical Application
20075201
*Refer to the Application Information Section for information concerning proper selection of the input and output coupling capacitors.
FIGURE 1. Typical Audio Amplifier Application Circuit
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2004 National Semiconductor Corporation DS200752
www.national.com
1 page  
External Components Description (Figure 1)
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Components Functional Description
1. Ri
2. Ci
3. Rf
4. CS
The inverting input resistance, along with Rf, set the closed-loop gain. Ri, along with Ci, form a high
pass filter with fc = 1/(2πRiCi).
The input coupling capacitor blocks DC voltage at the amplifier’s input terminals. Ci, along with Ri,
create a highpass filter with fC = 1/(2πRiCi). Refer to the section, Selecting Proper External
Components, for an explanation of determining the value of Ci.
The feedback resistance, along with Ri, set closed-loop gain.
This is the supply bypass capacitor. It provides power supply filtering. Refer to the Application
Information section for proper placement and selection of the supply bypass capacitor.
This is the half-supply bypass pin capacitor. It provides half-supply filtering. Refer to the section,
5. CB
6. CO
7. RB
Selecting Proper External Components, for information concerning proper placement and selection
of CB.
This is the output coupling capacitor. It blocks the DC voltage at the amplifier’s output and forms a high
pass filter with RL at fO = 1/(2πRLCO)
This is the resistor which forms a voltage divider that provides 1/2 VDD to the non-inverting input of the
amplifier.
Typical Performance
Characteristics
THD+N vs Frequency
VDD = 2.6V, PWR = 15mW, RL = 8Ω
THD+N vs Frequency
VDD = 2.6V, PWR = 15mW, RL = 16Ω
20075267
20075268
5 www.national.com
5 Page 
Typical Performance Characteristics (Continued)
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PSRR vs Frequency
VDD = 5V, RL = 32Ω, VRIPPLE = 100mVpp
Pins 3 and 5 directly driven, Inputs Floating
PSRR vs Frequency
VDD = 5V, RL = 32Ω, VRIPPLE = 100mVpp
Inputs Terminated
20075296
Open Loop Frequency Response
VDD = 5V, RL = 8Ω
20075297
Open Loop Frequency Response
VDD = 5V, RL = 32Ω
20075298
Open Loop Frequency Response
VDD = 5V, RL = 5kΩ
Supply Current vs
Supply Voltage (no Load)
20075299
200752A0
11
200752A1
www.national.com
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| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet LM4908.PDF ] | |
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