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參數(shù)資料
| 型號： | TPA112DGN |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 0.07 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO8 |
| 封裝： | GREEN, PLASTIC, MSOP-8 |
| 文件頁數(shù)： | 11/29頁 |
| 文件大小： | 707K |
| 代理商： | TPA112DGN |
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APPLICATION INFORMATION
GAIN SETTING RESISTORS, RF and RI
Gain + *
R
F
R
I
(1)
Effective Impedance +
R
FRI
R
F ) RI
(2)
f
co(lowpass) +
1
2p R
F CF
(3)
INPUT CAPACITOR, CI
f
co(highpass) +
1
2p R
I
C
I
(4)
C
I +
1
2p R
I
f
co(highpass)
(5)
TPA112
SLOS212E – AUGUST 1998 – REVISED JUNE 2004
The gain for the TPA112 is set by resistors RF and RI according to Equation 1.
Given that the TPA112 is an 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 fco(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 0.4 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
that the source dc level. It is important to confirm the capacitor polarity in the application.
19
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TPA112DGNG4 | 功能描述:音頻放大器 150mW Stereo Aud Power Amp RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| TPA112DGNR | 功能描述:音頻放大器 150mW Stereo RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| TPA112DGNRG4 | 功能描述:音頻放大器 150mW Stereo RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| TPA112DR | 功能描述:音頻放大器 150mW Stereo RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| TPA112DRG4 | 功能描述:音頻放大器 150mW Stereo RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
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