参数资料
型号: TPA6111A2DGN
厂商: TEXAS INSTRUMENTS INC
元件分类: 音频/视频放大
英文描述: 0.15 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO8
封装: GREEN, PLASTIC, MSOP-8
文件页数: 7/26页
文件大小: 804K
代理商: TPA6111A2DGN
www.ti.com
APPLICATION INFORMATION
GAIN SETTING RESISTORS, RF and Ri
Gain + *
R
F
R
I
(1)
Effective Impedance +
R
FRI
R
F ) RI
(2)
f
c(lowpass) +
1
2p R
F
C
F
(3)
INPUT CAPACITOR, Ci
f
c(highpass) +
1
2p R
I
C
I
(4)
C
I +
1
2p R
I
f
c(highpass)
(5)
TPA6111A2
SLOS313B – DECEMBER 2000 – REVISED JUNE 2004
The gain for the TPA6111A2 is set by resistors RF and RI according to Equation 1.
Given that the TPA6111A2 is a MOS amplifier, the input impedance is high. Consequently, input leakage
currents are not generally a concern, although noise in the circuit increases as the value of RF increases. In
addition, a certain range of RF values is required for proper start-up operation of the amplifier. Taken together it
is recommended that the effective impedance seen by the inverting node of the amplifier be set between 5 k
and 20 k
. The effective impedance is calculated in Equation 2.
As an example, consider an input resistance of 20 k
and a feedback resistor of 20 k. The gain of the amplifier
would be –1 and the effective impedance at the inverting terminal would be 10 k
, which is within the
recommended range.
For high-performance applications, metal film resistors are recommended because they tend to have lower noise
levels than carbon resistors. For values of RF above 50 k, the amplifier tends to become unstable due to a pole
formed from RF and the inherent input capacitance of the MOS input structure. For this reason, a small
compensation capacitor of approximately 5 pF should be placed in parallel with RF. In effect, this creates a
low-pass filter network with the cutoff frequency defined in Equation 3.
For example, if RF is 100 k and CF is 5 pF, then fc(lowpass) is 318 kHz, which is well outside the audio range.
In the typical application, input capacitor CI is required to allow the amplifier to bias the input signal to the proper
dc level for optimum operation. In this case, Ci and RI form a high-pass filter with the corner frequency
determined in Equation 4.
The value of CI is important to consider, as it directly affects the bass (low-frequency) performance of the circuit.
Consider the example where RI is 20 k and the specification calls for a flat bass response down to 20 Hz.
Equation 4 is reconfigured as Equation 5.
In this example, CI is 0.40 F, so one would likely choose a value in the range of 0.47 F to 1 F. A further
consideration for this capacitor is the leakage path from the input source through the input network (RI, CI) and
the feedback resistor (RF) 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 (> 10). For this reason a low-leakage tantalum
or ceramic capacitor is the best choice. When polarized capacitors are used, the positive side of the capacitor
should face the amplifier input in most applications, as the dc level there is held at VDD/2, which is likely higher
than the source dc level. Note that it is important to confirm the capacitor polarity in the application.
15
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TPA6111A2DGNRG4 功能描述:音频放大器 Stereo Headphone Pin Compat RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel
TPA6111A2DR 功能描述:音频放大器 150mW Stereo Power RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel