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Inverting: zero at -2, pole at -5, HF gain 2

Short answer

For the inverting realization of −2(s+2)/(s+5): R1=25 kΩ, C1=20 μF (input parallel), R2=20 kΩ, C2=10 μF (feedback). HF gain2, zero −2, pole −5. Add inverter for positive sign.

Realize a system using inverting op-amp configuration with zero at s = -2 and pole at s = -5 and having high frequency gain of 2.

Required function: zero at s=−2s=-2, pole at s=−5s=-5, HF gain 2:

T(s)=2 s+2s+5(DC gain 0.8)T(s) = 2\,\frac{s+2}{s+5} \quad(\text{DC gain } 0.8)

Inverting configuration: Z1Z_1 from the input to the inverting input, Z2Z_2 in feedback:

T(s)=−Z2Z1=−Y1Y2T(s) = -\frac{Z_2}{Z_1} = -\frac{Y_1}{Y_2}

With Y1=1R1+sC1Y_1 = \dfrac{1}{R_1} + sC_1 (parallel R1C1R_1C_1) and Y2=1R2+sC2Y_2 = \dfrac{1}{R_2} + sC_2 (parallel R2C2R_2C_2):

T(s)=−C1C2⋅s+1R1C1s+1R2C2T(s) = -\frac{C_1}{C_2}\cdot\frac{s + \frac{1}{R_1C_1}}{s + \frac{1}{R_2C_2}}
              +---R2---+
              |        |
              +---||---+
       R1     |   C2   |
  +--/\/\--+  |        |
Vin        +--+-|-\    |
  +---||---+    |  >---+--- Vo
       C1   GND-|+/

Matching:

C1C2=21R1C1=21R2C2=5\begin{aligned} \frac{C_1}{C_2} &= 2 \\ \frac{1}{R_1C_1} &= 2 \\ \frac{1}{R_2C_2} &= 5 \end{aligned}

Normalized: C2=1C_2 = 1 F, C1=2C_1 = 2 F, R1=12×2=0.25 ΩR_1 = \dfrac{1}{2\times2} = 0.25\ \Omega, R2=0.2 ΩR_2 = 0.2\ \Omega.

Practical values (impedance scale km=105k_m = 10^5, C→C/kmC \to C/k_m):

ElementNormalizedFinal
R1R_10.25 Ω25 kΩ
C1C_12 F20 μF
R2R_20.2 Ω20 kΩ
C2C_21 F10 μF

Check: DC gain =R2/R1=0.8=2×2/5= R_2/R_1 = 0.8 = 2 \times 2/5; HF gain =C1/C2=2= C_1/C_2 = 2.

Answer: R1=25 kΩR_1 = 25\ \text{k}\Omega, C1=20 μC_1 = 20\ \muF, R2=20 kΩR_2 = 20\ \text{k}\Omega, C2=10 μC_2 = 10\ \muF, realizing −2(s+2)/(s+5)-2(s+2)/(s+5). The minus sign is the 180° phase inversion of this configuration; a unity-gain inverter can follow if a positive sign is needed.

✓ Answer checked by Claude Sonnet 5.5

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