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| NS LME49600高保真耳机放大方案 |
| 作者： 时间：2008-08-25 来源:eaw |
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NS公司的LME49600高保真耳机放大器是可提供高性能低失真250mA的音频缓冲器。它的低失真（THD+N）可达0.00003%，转换速率高达2000V/μs，典型带宽可达180MHz，可用作耳机放大器输出级，线路驱动器，低功率音频放大器，大电流运放输出级以及电源稳压器。本文介绍了LME49600的主要指标和特性，功能方框图，用作音频缓冲器的电路图，以及耳机放大器电路图。此外，还介绍了LME49600评估板电路图和材料清单（BOM）。
LME49600 High Performance, High Fidelity, High Current Audio Buffer The LME49600 is a high performance, low distortion high fidelity 250mA audio buffer. The LME49600 is designed for a wide range of applications. It can be used inside the feedback loop of op amps.
The LME49600 offers a pin-selectable bandwidth: a low current, 110MHz bandwidth mode that consumes 7.3mA and a wide 180MHz bandwidth mode that consumes 13.2mA. In both modes the LME49600 has a nominal 2000V/μs slew rate. Bandwidth is easily adjusted by either leaving the BW pin unconnected or connecting a resistor between the BW pin and the VEE pin.
The LME49600 is fully protected through internal current limit and thermal shutdown.
LME49600主要指标：
■Low THD+N (VOUT = 3VRMS, f = 1kHz, Figure 2) 0.00003% (typ)
■Slew Rate 2000V/μs (typ)
■High Output Current 250mA (typ)
■Bandwidth
BW pin floating 110MHz (typ)
BW connected to VEE 180MHz (typ)
■Supply Voltage Range ±2.25V ≤ VS ≤ ±18V
LME49600主要特性：
■Pin-selectable bandwidth and quiescent current
■Pure fidelity. Pure performance
■Short circuit protection
■Thermal shutdown
■TO–263 surface-mount package
应用：
■Headphone amplifier output drive stage
■Line drivers
■Low power audio amplifiers
■High-current operational amplifier output stage
■ATE Pin Driver Buffer
■Power supply regulator
图1。LME49600功能方框图
图2。高性能高保真LME49600用作音频缓冲器的电路图
图3。高输出电流高性能LME49600耳机放大器电路图
LME49600评估板
To help the user investigate and evaluate the LME49600s performance and capabilities, a fully populated demonstration board was created. Please contact the National Semiconductor Corporations Audio Products Group for availability. This board is shown in Figure 1. Connected to an external power supply (±2.5V to ±17V ) and a signal source. The LME49600 demonstration board easily demonstrates the amplifiers features. The LME49600 is a high performance, low distortion high fidelity 250mA audio buffer. Whereas there are many uses for the LME49600, this application note describes a headphone amplifier circuit and associated demonstration board. Designed 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 current, 110MHz bandwidth mode that consumes 8mA and a wide 180MHz bandwidth mode that consumes 15mA. In both modes the LME49600 has a nominal 2000V/μs slew rate.
Bandwidth is easily adjusted by either leaving the BW pin unconnected, connecting a resistor between the BW pin and the VEE pin or connecting the BW pin directly to the VEE pin.
The LME49600 is fully protected through internal current limit and thermal shutdown.
Operating Conditions
■Temperature Range –40°C ≤ TA ≤ 85°C
■Amplifier Power
Supply Voltage 2.5V ≤ VS ±17V
LME49600评估板主要特性：
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 input 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.
图4。LME49600评估板外形图
图5。LME49600评估板电路图
LME49600评估板材料清单
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