4

1

C

3

4

2

5

R

Gain

R

1

f

1 R R C C

2S

1 3

2

5

2

2

1

3

4

3

4

2

5

1 R R C C

Output

s

Input

s

s C

1 R

1 R

1 R

1 R R C C

+

±

OPA202

Output

Input

R1

590

R4

2.94 k

R3

499

C2

39 nF

C5

1 nF

Copyright © 2017, Texas Instruments Incorporated

28

OPA202, OPA2202, OPA4202

SBOS812E – OCTOBER 2017 – REVISED FEBRUARY 2020

www.ti.com

Product Folder Links: OPA202 OPA2202 OPA4202

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Copyright © 2017–2020, Texas Instruments Incorporated

8.2 Typical Application

Figure 47. 25-kHz, Low-Pass Filter

8.2.1 Design Requirements

Low-pass filters are used in signal processing applications to reduce noise and prevent aliasing. The OPAx202

devices are is designed to construct high-speed, high-precision active filters. Figure 47 shows a second-order,

low-pass filter commonly encountered in signal processing applications.

Use the following parameters for this design example:

•

Gain = 5 V/V (inverting gain)

•

Low-pass cutoff frequency = 25 kHz

•

Second-order Chebyshev filter response with 3-dB gain peaking in the passband

8.2.2 Detailed Design Procedure

The infinite-gain multiple-feedback circuit for a low-pass network function is shown in Figure 47. Use Equation 1

to calculate the voltage transfer function.

(1)

This circuit produces a signal inversion. For this circuit, the gain at DC and the low-pass cutoff frequency are

calculated by Equation 2:

(2)

and easy-to-use active filter design program. The WEBENCH® Filter Designer lets you create optimized filter

designs using a selection of TI operational amplifiers and passive components from TI's vendor partners.

Available as a web based tool from the WEBENCH Design Center, WEBENCH Filter Designer allows you to

design, optimize, and simulate complete multistage active filter solutions within minutes.