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"Chapter 1 - The Op Amp's Place in the World" - HTL Wien 10

"Chapter 1 - The Op Amp's Place in the World" - HTL Wien 10

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With C 1 = 330 pF and C 2 = 4.7 nF, <strong>the</strong> values for R1 and R2 are:<br />

R1 = 1.45 kΩ, with <strong>the</strong> closest 1% value be<strong>in</strong>g 1.47 kΩ<br />

R2 = 4.51 kΩ, with <strong>the</strong> closest 1% value be<strong>in</strong>g 4.53 kΩ<br />

Figure 16–22 shows <strong>the</strong> f<strong>in</strong>al filter circuit with its partial filter stages.<br />

3.16k<br />

VIN 1.87k 4.42k<br />

1n<br />

820p<br />

1.5n<br />

1.47k 4.53k<br />

Figure 16–22. Fifth-Order Unity-Ga<strong>in</strong> Butterworth Low-Pass Filter<br />

16.4 High-Pass Filter Design<br />

V IN<br />

R 1<br />

330p<br />

Active Filter Design Techniques<br />

High-Pass Filter Design<br />

By replac<strong>in</strong>g <strong>the</strong> resistors of a low-pass filter with capacitors, and its capacitors with resistors,<br />

a high-pass filter is created.<br />

R 2<br />

C 1<br />

C 2<br />

V OUT<br />

Figure 16–23. Low-Pass to High-Pass Transition Through Components Exchange<br />

V IN<br />

To plot <strong>the</strong> ga<strong>in</strong> response of a high-pass filter, mirror <strong>the</strong> ga<strong>in</strong> response of a low-pass filter<br />

at <strong>the</strong> corner frequency, Ω=1, thus replac<strong>in</strong>g Ω with 1/Ω and S with 1/S <strong>in</strong> Equation 16–1.<br />

C 1<br />

C 2<br />

R 1<br />

4.7n<br />

R 2<br />

V OUT<br />

V OUT<br />

16-21

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