NS公司的LME49600高保真耳機放大器是可提供高性能低失真250mA的音頻緩沖器。它的低失真（THD+N）可達0.00003%，轉換速率高達2000V/μs，典型帶寬可達180MHz，可用作耳機放大器輸出級，線路驅動器，低功率音頻放大器，大電流運放輸出級以及電源穩壓器。本文介紹了LME49600的主要指標和特性，功能方框圖，用作音頻緩沖器的電路圖，以及耳機放大器電路圖。此外，還介紹了LME49600評估板電路圖和材料清單（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主要指標：
■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
應用：
■Headphone amplifier output drive stage
■Line drivers
■Low power audio amplifiers
■High-current operational amplifier output stage
■ATE Pin Driver Buffer
■Power supply regulator
圖1。LME49600功能方框圖
圖2。高性能高保真LME49600用作音頻緩沖器的電路圖
圖3。高輸出電流高性能LME49600耳機放大器電路圖
LME49600評估板
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評估板主要特性：
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.
圖4。LME49600評估板外形圖
圖5。LME49600評估板電路圖
LME49600評估板材料清單
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