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APA2065 参数 Datasheet PDF下载

APA2065图片预览
型号: APA2065
PDF下载: 下载PDF文件 查看货源
内容描述: 立体声2.7瓦音频功率放大器(带DC_Volume控制) [Stereo 2.7-W Audio Power Amplifier (with DC_Volume Control)]
分类和应用: 放大器功率放大器
文件页数/大小: 25 页 / 449 K
品牌: ANPEC [ ANPEC ELECTRONICS COROPRATION ]
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APA2065  
Application Descriptions (Cont.)  
Input Resistance, Ri (Cont.)  
The value of Ci is important to consider as it directly  
affects the low frequency performance of the circuit.  
Consider the example where Ri is 10kW and the  
specification calls for a flat bass response down to  
100Hz. Equation is reconfigured as follow :  
RF  
Ri  
RF  
Ri  
(2)  
(3)  
-
=
AV  
SE Gain =  
-2 x  
=
BTL Gain  
BTL mode operation brings the factor of 2 in the gain  
equation due to the inverting amplifier mirroring the  
voltage swing across the load. For the varying gain  
setting, APA2065 generates each input resistance  
on figure 4. The input resistance will affect the low  
frequency performanceof audio signal.The minmum  
input resistance is 10kW when gain setting is 20dB  
and the resistance will ramp up when close loop gain  
below 20dB. The input resistance has wide variation  
(+/-10%) caused by process variation.  
1
(5)  
Ci=  
2px10kWxfC  
Consider to input resistance variation, the Ci is 0.16mF  
so one would likely choose a value in the range  
of 0.22mF to 1.0mF.  
Afurther consideration for this capacitor is the leakage  
path from the input source through the input network  
(Ri+Rf, Ci) to the load. This leakage current creates a  
DC offset voltage at the input to the amplifier that  
reduces useful headroom, especially in high gain  
applications. For this reason a low-leakage tantalum  
or ceramiccapacitor isthe best choice. When polarized  
capacitors are used, the positive side of the capacitor  
should face the amplifier input in most applications as  
theDC level thereisheld atVDD/2, whichislikelyhigher  
that thesourceDC level. Pleasenotethat it isimportant  
to confirm the capacitor polarity in the application.  
Ri vs Gain(BTL)  
Ri(k )  
W
120  
100  
80  
60  
40  
20  
0
Effective BypassCapacitor, Cbypass  
As other power amplifiers, proper supply bypassing is  
critical for low noise performance and high power  
supply rejection.  
-40  
-30  
-20  
-10  
0
10  
20  
Gain(dB)  
Figure 4: Input resistance vsGain setting  
Input Capacitor, Ci  
The capacitors located on both the bypass and power  
supply pins should be as close to the device as  
possible. The effect of a larger bypass capacitor will  
improve PSRR due to increased supply stability.  
Typical applicationsemploy a 5V regulator with 1.0mF  
and a 0.1mF bypass capacitor as supply filtering. This  
does not eliminate the need for bypassing the supply  
nodes of the APA2065. The selection of bypass  
capacitors, especially Cbypass, is thus dependent  
upon desired PSRR requirements, click and pop  
performance.  
In the typical application an input capacitor, Ci, is  
required to allowtheamplifier to biasthe input signal to  
theproperDC level for optimum operation. In thiscase,  
Ci andthe minimum input impedance Ri (10kW) form a  
high-passfilter with the corner frequency determined in  
thefollowequation:  
1
(4)  
FC(highpass)=  
2px10kWxCi  
Copyright ã ANPEC Electronics Corp.  
17  
www.anpec.com.tw  
Rev. A.4 - Aug., 2005  
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