參數(shù)資料
型號(hào): TPA721D
廠商: TEXAS INSTRUMENTS INC
元件分類: 音頻/視頻放大
英文描述: 0.7 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8
封裝: GREEN, PLASTIC, MS-012AA, SOIC-8
文件頁(yè)數(shù): 7/26頁(yè)
文件大?。?/td> 663K
代理商: TPA721D
www.ti.com
APPLICATION SCHEMATICS
Audio
Input
Bias
Control
VDD
700 mW
6
5
7
VO+
VDD
1
2
4
BYPASS
IN–
VDD/2
CI
CS
1
F
CB
2.2
F
SHUTDOWN
VO– 8
GND
From System Control
3
IN+
RI
10 k
RF
50 k
+
+
COMPONENT SELECTION
Gain-Setting Resistors, RF and RI
BTL gain + * 2
R
F
R
I
(5)
Effective impedance +
R
F
R
I
R
F )
R
I
(6)
TPA721
SLOS231E – NOVEMBER 1998 – REVISED JUNE 2004
Figure 26 is a schematic diagram of a typical handheld audio application circuit, configured for a gain of –10 V/V.
Figure 26. TPA721 Application Circuit
The following sections discuss the selection of the components used in Figure 26.
The gain for each audio input of the TPA721 is set by resistors RF and RI according to Equation 5 for BTL mode.
BTL mode operation brings about the factor 2 in the gain equation due to the inverting amplifier mirroring the
voltage swing across the load. Given that the TPA721 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 startup 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 6.
As an example, consider an input resistance of 10 k
and a feedback resistor of 50 k. The BTL gain of the
amplifier would be –10 V/V, and the effective impedance at the inverting terminal would be 8.3 k
, which is well
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 when RF is greater than
50 k
. This, in effect, creates a low-pass filter network with the cutoff frequency defined in Equation 7.
15
相關(guān)PDF資料
PDF描述
TPA721DGN 0.7 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8
TPA721DGNR 0.7 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8
TPA721DR 0.7 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8
TPA721DG4 0.7 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8
TPA721DGNG4 0.7 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8
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