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参数资料
| 型号： | PGA2500IDBG4 |
| 英文描述： | Digitally Controlled Microphone Preamplifier |
| 中文描述： | 数控麦克风前置放大器 |
| 文件页数： | 12/17页 |
| 文件大小： | 206K |
| 代理商： | PGA2500IDBG4 |
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SBOS289A NOVEMBER 2003 REVISED DECEMBER 2003
www.ti.com
12
INPUT CIRCUIT CONSIDERATIONS
The input circuit for the PGA2500 must include several
items that are common to most microphone preamplifiers.
Figure 7 shows a typical input circuit configuration. Other
functions, such as input attenuation (pads), filters, and
polarity reversal switches are commonly found in
preamplifier circuits, but are not shown here in order to
focus on the basic input circuit requirements.
The microphone input is typically taken from a balanced
XLR or TRS input connection (XLR shown). The 1000pF
capacitors provide simple EMI filtering for the circuit.
Additional filtering for low- or high-frequency noise may be
added, depending upon the end application environment.
A bridging resistor is shown and may be selected to
provide the desired overall input impedance required for a
given microphone. This resistance will be in parallel with
the phantom power bias resistors and the PGA2500 input
resistance to set the actual impedance seen by the
microphone.
Connections for +48V phantom power, required for
condenser microphones, are shown in Figure 7. The
phantom power requires an On/Off switch, as dynamic
microphones do not require phantom power and may be
damaged if power is applied. DC-blocking capacitors are
required between the phantom power connections and the
PGA2500 inputs. The blocking capacitors are selected to
have a high working voltage rating, with 50V being the
minimum and 63V recommended for long term reliability.
The blocking capacitors, along with the PGA2500 input
resistance, form a high-pass filter circuit. With the typical
input resistance of the PGA2500 specified in the Electrical
Characteristics table, the value of the capacitor can be
chosen to meet the desired low frequency response for the
end application. At the same time, the value should be no
higher than required, since larger capacitors store more
charge and increase the surge current seen at the
preamplifier when a short circuit occurs on the microphone
input connector.
To protect the PGA2500 from large surge currents, power
Schottky diodes are placed on the input pins to both the
VA+ and VA power supplies. Schottky diodes are used
due to their lower turn-on voltage compared to standard
rectifier diodes. Power devices are required since the
surge currents from a large valued blocking capacitor
(47
μ
F) can exceed 4.5 amps for a very short duration of
time. It is recommended that the Schottky diode chosen for
this application be specified for at least a 10A surge
current.
The use of a series current-limiting resistor prior to the
protection diodes will aid in handling surge currents,
although the resistor will add noise to the circuit. Select a
current-liming resistor value that is as high as tolerable for
the desired noise performance of the preamplifier circuit.
(3)
6.81k
0.25W
(4)
(4)
(4)
(4)
(3)
10
μ
F
47
μ
F
63WV
+
+
10
μ
F
47
μ
F
63WV
1
Mic Input
2
3
1000pF
1000pF
1000pF
6.81k
0.25W
Phantom
Power
Switch
+48V
(1)
(2)
(2)
VA+
VA
V
IN
+
V
IN
NOTES: (1) Bridging resistor, used to set the impedance seen by the microphone.
(2) The blocking capacitor value is selected based upon the desired low frequency response.
(3) Currentimiting resistor. Select the highest value tolerable based upon input noise requirements.
(4) Schottky diode, selected for fast turnon and rated for a minimum of a 10A surge current.
Recommended device is the MBRA120LT3 from ON Semiconductor.
Figure 7. Typical Input Circuit for the PGA2500
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PDF描述 |
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| PGA2500IDBRG4 | Digitally Controlled Microphone Preamplifier |
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| PGA4311UA1 | 4-Channel Audio Volume Control |
| PGA4311UAG4 | 4-Channel Audio Volume Control |
| PGA4311UG4 | 4-Channel Audio Volume Control |
相关代理商/技术参数 |
参数描述 |
|---|---|
| PGA2500IDBR | 功能描述:传声器前置放大器 0dB & 10dB-65dB in 1dB steps RoHS:否 制造商:Texas Instruments 可用增益调整:Digital control, 65 dB to 0 dB 共模抑制比（最小值）: 输入补偿电压: 最大输入电阻:9200 Ohms 最大工作温度:+ 85 C 封装 / 箱体:SSOP-28 封装:Tube |
| PGA2500IDBRG4 | 功能描述:传声器前置放大器 0dB & 10dB-65dB in 1dB steps RoHS:否 制造商:Texas Instruments 可用增益调整:Digital control, 65 dB to 0 dB 共模抑制比（最小值）: 输入补偿电压: 最大输入电阻:9200 Ohms 最大工作温度:+ 85 C 封装 / 箱体:SSOP-28 封装:Tube |
| PGA2505 | 制造商:TI 制造商全称:Texas Instruments 功能描述:Digitally-Controlled MICROPHONE PREAMPLIFIER |
| PGA2505EVM | 功能描述:音频 IC 开发工具 PGA2505 Eval Mod RoHS:否 制造商:Texas Instruments 产品:Evaluation Kits 类型:Audio Amplifiers 工具用于评估:TAS5614L 工作电源电压:12 V to 38 V |
| PGA2505IDB | 功能描述:传声器前置放大器 Dig-Controlled Micro phone Preamp RoHS:否 制造商:Texas Instruments 可用增益调整:Digital control, 65 dB to 0 dB 共模抑制比（最小值）: 输入补偿电压: 最大输入电阻:9200 Ohms 最大工作温度:+ 85 C 封装 / 箱体:SSOP-28 封装:Tube |
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