差分电压采样

差分电压采样

0 概述

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采样在电力电子控制中至关重要，而采样就离不开差分。差分运算放大电路，对共模信号得到有效抑制，而只对差分信号进行放大，因而得到广泛的应用。

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$$V_o = \dfrac{R_f}{R_1} \cdot \left ( V_p - V_n \right ) + V_{ref} \tag{0-1}$$

1 叠加定理

1.1 $V_{inp} \neq 0 ,V_{inn} = 0,V_{ref} = 0$

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$$V_p = V_{inp }\cdot \dfrac{R_f}{R_1 + R_f} = V_n \tag{1-1}$$$$i_{in} = \dfrac{V_n-0}{R_1} \tag{1-2}$$$$V_{o1} = i_{in} \cdot (R_1 + R_f) = \dfrac{\dfrac{V_{inp} \cdot R_f}{R_1 + R_f}}{R_1} \cdot {R_1+R_f}= V_{inp} \cdot \dfrac{R_f}{R_1} \tag{1-3}$$

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1.2 $V_{inn} \neq 0 ,V_{inp} = 0,V_{ref} = 0$

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$$V_p = 0 =V_n \tag{1-4}$$$$i_{in} = \dfrac{V_n-V_{inn}}{R_1} \tag{1-5}$$$$V_{o2} = V_{inn} + i_{in} \cdot (R_1 + R_f) = V_{inn} + \dfrac{0-V_{inn}}{R_1} \cdot (R_1+R_f) = - V_{inn} \cdot \dfrac{R_f}{R_1} \tag{1-6}$$

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1.3 $ V_{ref} \neq 0 ,V_{inp} = 0,V_{inn} = 0$

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$$V_p = V_{ref} \cdot \dfrac{R_1}{R_1 + R_f} = V_n \tag{1-7}$$$$i_{in} = \dfrac{V_n-0}{R_1} \tag{1-8}$$$$V_{o3} = i_{in} \cdot (R_1 + R_f) = \dfrac{\dfrac{V_{ref} \cdot R_1}{R_1 + R_f}}{R_1} \cdot {R_1+R_f}= V_{ref} \tag{1-9}$$

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1.4 叠加可得到

$$V_o = V_{o1} + V_{o2} + V_{o3} = V_o = \dfrac{R_f}{R_1} \cdot \left ( V_p - V_n \right ) + V_{ref} \tag{1-10}$$

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2 常用差分IC

2.1 INA199

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2.2 INA240