AGPS11C 高压变频器保护板用于保护电压稳定

AGPS11C 高压变频器保护板用于保护电压稳定 

AGPS11C 高压变频器保护板用于保护电压稳定 

AGPS11C 高压变频器保护板用于保护电压稳定 

按照表1中列出的设计要求设计高带宽、高增益、电压放大器
此处选择放大器配置；然而，该理论也适用于非反相配置。
在反相配置中，信号增益和噪声增益传递函数不相等，不同于
非反相配置。
表1.设计要求
目标带宽
（MHz）信号增益（V/V）反馈电阻
(Ω)
频率
峰值（dB）
> 750 –2 453 < 2
10.2.2详细设计程序
OPA858被补偿为在7V/V的增益中具有小于1dB的峰值。在下部使用设备
增益导致峰值和潜在不稳定性增加。图59显示了信号中配置的OPA858
增益为-2 V/V。放大器的直流噪声增益（1/β）受62Ω端接电阻器和50Ω端接电阻的影响
源电阻，由等式1给出。在较高频率下，噪声增益受电抗元件的影响
例如电感器和电容器。这些包括离散电路板组件和印刷电路板
（PCB）寄生。
(1)
频率（Hz）
模拟响应
测量响应
频率（Hz）
归一化增益（dB）
www.ti.com.SBOS629A–2018年4月–2018年7月修订
产品文件夹链接：OPA858
版权所有©2018，德克萨斯仪器公司提交文件反馈
放大器的稳定性和相位裕度取决于放大器的环路增益，它是
放大器的AOL和反馈因子（β）。负反馈回路系统的β是
反馈到输入端的输出信号，在放大器的情况下，是噪声增益的倒数。这个
通过增加输入电容器和反馈，可以提高放大器在高频下的噪声增益
电容器如图60所示。如果小心操作，增加1/β可以改善相位裕度，就像任何放大器一样
与单位增益缓冲器配置相比，在高增益配置中更稳定。具有
增加的电容器改变高频噪声增益，但不改变信号增益。AN-1604
失补偿运算放大器应用报告提供了噪声增益整形的详细分析
失补偿放大器的技术，并展示如何选择外部电阻和电容值。
图61显示了如图59所示配置的OPA858的未补偿频率响应。
在没有任何附加噪声增益整形组件的情况下，OPA858显示约13dB的峰值。
图62显示了OPA858的噪声增益补偿频率响应，配置如所示
图60.噪声增益整形元件将峰值降低至小于1.5 dB。2.7pF输入电容器，
放大器的输入电容、增益电阻器和反馈电阻器在噪声增益中产生零
如等式2所示，频率为f。Design a high-bandwidth, high-gain, voltage amplifier with the design requirements listed in Table 1. An inverting
amplifier configuration is chosen here; however, the theory is applicable to a noninverting configuration as well.
In an inverting configuration the signal gain and noise gain transfer functions are not equal, unlike the
noninverting configuration.
Table 1. Design Requirements
TARGET BANDWIDTH
(MHz) SIGNAL GAIN (V/V) FEEDBACK RESISTANCE
(Ω)
FREQUENCY
PEAKING (dB)
> 750 –2 453 < 2
10.2.2 Detailed Design Procedure
The OPA858 is compensated to have less than 1 dB of peaking in a gain of 7 V/V. Using the device in lower
gains results in increased peaking and potential instability. Figure 59 shows the OPA858 configured in a signal
gain of –2 V/V. The DC noise gain (1/β) of the amplifier is affected by the 62-Ω termination resistor and the 50-Ω
source resistor and is given by Equation 1. At higher frequencies the noise gain is affected by reactive elements
such as inductors and capacitors. These include both discrete board components as well as printed circuit board
(PCB) parasitics.
(1)
Frequency (Hz)
Simulated Response
Measured Response
Frequency (Hz)
Normalized Gain (dB)
www.ti.com SBOS629A –APRIL 2018–REVISED JULY 2018
Product Folder Links: OPA858
Copyright © 2018, Texas Instruments Incorporated Submit Documentation Feedback
The stability and phase margin of the amplifier depend on the loop gain of the amplifier, which is the product of
the AOL and the feedback factor (β) of the amplifier. The β of a negative-feedback loop system is the portion of
the output signal that is fed back to the input, and in the case of an amplifier is the inverse of the noise gain. The
noise gain of the amplifier at high frequencies can be increased by adding an input capacitor and a feedback
capacitor as Figure 60 shows. If done carefully, increasing 1/β improves the phase margin just as any amplifier is
more stable in a high gain configuration versus a unity-gain buffer configuration. The modified network with the
added capacitors alters the high-frequency noise gain, but does not alter the signal gain. The AN-1604
Decompensated Operational Amplifiers application report provides a detailed analysis of noise gain-shaping
techniques for decompensated amplifiers and shows how to choose external resistors and capacitor values.
Figure 61 shows the uncompensated frequency response of the OPA858 configured as shown in Figure 59.
Without any added noise gain shaping components, the OPA858 shows approximately 13 dB of peaking.
Figure 62 shows the noise gain compensated frequency response of the OPA858 configured as shown in
Figure 60. The noise gain shaping elements reduce the peaking to less than 1.5 dB. The 2.7-pF input capacitor,
the input capacitance of the amplifier, the gain resistor, and the feedback resistor create a zero in the noise gain
at a frequency f, as Equation 2 shows.