差分电压采样
0 概述
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。
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
V_p = V_{inp }\\cdot \\dfrac{R_f}{R_1 + R_f} = V_n \\tag{1-1}$$$$i_{in} = \\dfrac{V_n-0}{R_1} \\tag{1-2}$$$$V_{o1} = i_{in} \\cdot (R_1 + R_f) = \\dfrac{\\dfrac{V_{inp} \\cdot R_f}{R_1 + R_f}}{R_1} \\cdot {R_1+R_f}= V_{inp} \\cdot \\dfrac{R_f}{R_1} \\tag{1-3}
1.2 V_{inn} \\neq 0 ,V_{inp} = 0,V_{ref} = 0
V_p = 0 =V_n \\tag{1-4}$$$$i_{in} = \\dfrac{V_n-V_{inn}}{R_1} \\tag{1-5}$$$$V_{o2} = V_{inn} + i_{in} \\cdot (R_1 + R_f) = V_{inn} + \\dfrac{0-V_{inn}}{R_1} \\cdot (R_1+R_f) = - V_{inn} \\cdot \\dfrac{R_f}{R_1} \\tag{1-6}
1.3 V_{ref} \\neq 0 ,V_{inp} = 0,V_{inn} = 0
V_p = V_{ref} \\cdot \\dfrac{R_1}{R_1 + R_f} = V_n \\tag{1-7}$$$$i_{in} = \\dfrac{V_n-0}{R_1} \\tag{1-8}$$$$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}
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}
2 常用差分IC
2.1 INA199
2.2 INA240
