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参数资料
| 型号： | THS7002IPWP |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 模拟信号调理 |
| 英文描述： | SPECIALTY ANALOG CIRCUIT, PDSO28 |
| 封装： | GREEN, PLASTIC, HTSSOP-28 |
| 文件页数： | 11/41页 |
| 文件大小： | 1203K |
| 代理商： | THS7002IPWP |
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THS7001, THS7002
70MHz PROGRAMMABLEGAIN AMPLIFIERS
SLOS214C OCTOBER 1998 REVISED MARCH 2007
19
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
APPLICATION INFORMATION
optimizing frequency response for the preamplifiers (continued)
The next thing that helps to maintain a smooth frequency response is to keep the feedback resistor (Rf) and
the gain resistor (Rg) values fairly low. These two resistors are effectively in parallel when looking at the ac
small-signal response. This is why in a configuration with a gain of 5, a feedback resistor of 5.1 k
with a gain
resistor of 1.2 k
only shows a small peaking in the frequency response. The parallel resistance is less than
1 k
. This value, in conjunction with a very small stray capacitance test PCB, forms a zero on the edge of the
amplifier’s natural frequency response. To eliminate this peaking, all that needs to be done is to reduce the
feedback and gain resistances. One other way to compensate for this stray capacitance is to add a small
capacitor in parallel with the feedback resistor. This helps to neutralize the effects of the stray capacitance. To
keep this zero out of the operating range, the stray capacitance and resistor value’s time constant must be kept
low. But, as can be seen in Figures 14 19, a value too low starts to reduce the bandwidth of the amplifier. Table
1 shows some recommended feedback resistors to be used with the THS7001 and THS7002 preamplifiers.
Table 2. Recommended Feedback Resistors
GAIN
Rf for VCC = ±15 V and ± 5 V
2
499
1
499
5
1 k
PGA gain control
The PGA section of the THS7001 and THS7002 IC allows for digital control of the gain. There are three digital
control pins for each side of the PGA (AG0 – AG2, and BG0 – BG2). Standard TTL or CMOS Logic will control
these pins without any difficulties. The applied logic levels are referred to the DGND pins of the THS7002. The
gain functions are not latched and therefore always rely on the logic at these pins to maintain the correct gain
settings. A 3.3 k
resistor to ground is usually applied at each input to ensure a fixed logic state. The gain control
acts like break-before-make SPDT switches. Because of this action, the PGA will go into an open-loop condition.
This may cause the output to behave unpredictably until the switches closes in less than 1.5
s. Due to the
topology of this circuit, the controlling circuitry must be able to sink up to 2
A of current when 0-V is applied
to the gain control pin. A simplified circuit diagram of the gain control circuitry is shown in Figure 55.
+VCC
To Internal
Bias Circuitry
Control
VCC
DGND
Gain
Figure 55. Simplified PGA Gain Control
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相关代理商/技术参数 |
参数描述 |
|---|---|
| THS7002IPWPG4 | 功能描述:特殊用途放大器 70-MHz Hi-Spd Dual Prgrmbl-Gain Amp RoHS:否 制造商:Texas Instruments 通道数量:Single 共模抑制比（最小值）: 输入补偿电压: 工作电源电压:3 V to 5.5 V 电源电流:5 mA 最大功率耗散: 最大工作温度:+ 70 C 最小工作温度:- 40 C 安装风格:SMD/SMT 封装 / 箱体:QFN-20 封装:Reel |
| THS7002IPWPR | 功能描述:运算放大器 - 运放 70-MHz Programmable- Gain Dual RoHS:否 制造商:STMicroelectronics 通道数量:4 共模抑制比（最小值）:63 dB 输入补偿电压:1 mV 输入偏流（最大值）:10 pA 工作电源电压:2.7 V to 5.5 V 安装风格:SMD/SMT 封装 / 箱体:QFN-16 转换速度:0.89 V/us 关闭:No 输出电流:55 mA 最大工作温度:+ 125 C 封装:Reel |
| THS7002PWP | 制造商:TI 制造商全称:Texas Instruments 功能描述:70-MHz PROGRAMMABLE-GAIN AMPLIFIERS |
| THS7102 | 制造商:TI 制造商全称:Texas Instruments 功能描述:ADSL (POTS) CENTRAL OFFICE LINE INTERFACE DRIVER/RECEIVER |
| THS7103 | 制造商:TI 制造商全称:Texas Instruments 功能描述:ADSL (ISDN) CENTRAL OFFICE LINE INTERFACE DRIVER/RECEIVER |
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