803.92.00 HQQ 数据记录板用于数据传输

803.92.00 HQQ 数据记录板用于数据传输 

803.92.00 HQQ 数据记录板用于数据传输 

803.92.00 HQQ 数据记录板用于数据传输 

上面引用的应用程序报告和博客文章中的等式和计算器用于建模
配置为TIA的OPA858的带宽（f-3dB）和噪声（IRN）性能。结果性能为：
如图57和图58所示。左侧Y轴显示闭环带宽性能，而
图的右侧显示了集成输入参考噪声。计算IRN的噪声带宽，对于固定
RF和CPD设置为等于f–3dB频率。
图57显示了在RF=10 kΩ和20
kΩ。增加CPD会降低闭环带宽。减少任何杂散寄生电容至关重要
PCB以大化带宽。OPA858的设计总输入电容为0.8 pF，以使
对系统性能的影响。
图58显示了CPD=1 pF和2 pF时放大器性能随射频的变化。增加射频导致
较低带宽。为了大化光学前端系统中的信噪比（SNR），大化增益
在TIA阶段。将射频增加一倍“X”会使信号电平增加“X”，但只会增加电阻
“噪声贡献”√从而提高SNR。
 
1 453噪声增益＝＝1 2.79 V/V 5.04 dB
SBOS629A–2018年4月–2018年7月修订www.ti.com
产品文件夹链接：OPA858
提交文件反馈版权©2018，德克萨斯仪器公司
10.2典型应用
OPA858的高GBWP、低输入电压噪声和高转换速率使该器件成为可行的宽带、高性能和高性能的器件，
高输入阻抗电压放大器。
图59.增益为-2V/V的OPA858（无噪声增益整形）
图60.增益为-2V/V的OPA858（具有噪声增益整形）
10.2.1设计要求
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）parasitThe equations and calculators in the application report and blog posts referenced above are used to model the
bandwidth (f-3dB) and noise (IRN) performance of the OPA858 configured as a TIA. The resultant performance is
shown in Figure 57 and Figure 58. The left side Y-axis shows the closed-loop bandwidth performance, while the
right side of the graph shows the integrated input referred noise. The noise bandwidth to calculate IRN, for a fixed
RF and CPD is set equal to the f–3dB frequency.
Figure 57 shows the amplifier performance as a function of photodiode capacitance (CPD) for RF = 10 kΩ and 20
kΩ. Increasing CPD decreases the closed-loop bandwidth. It is vital to reduce any stray parasitic capacitance from
the PCB to maximize bandwidth. The OPA858 is designed with 0.8 pF of total input capacitance to minimize the
effect on system performance.
Figure 58 shows the amplifier performance as a function of RF for CPD = 1 pF and 2 pF. Increasing RF results in
lower bandwidth. To maximize the signal-to-noise ratio (SNR) in an optical front-end system, maximize the gain
in the TIA stage. Increasing RF by a factor of "X" increases the signal level by "X", but only increases the resistor
noise contribution by "√X", thereby improving SNR.
 
1 453 Noise Gain = = 1 2.79 V/V 5.04 dB
SBOS629A –APRIL 2018–REVISED JULY 2018 www.ti.com
Product Folder Links: OPA858
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10.2 Typical Application
The high GBWP, low input voltage noise and high slew rate of the OPA858 makes the device a viable wideband,
high input impedance voltage amplifier.
Figure 59. OPA858 in a Gain of –2V/V (No Noise Gain Shaping)
Figure 60. OPA858 in a Gain of –2V/V (With Noise Gain Shaping)
10.2.1 Design Requirements
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) parasit