8.2 Typical Applications

8.2.1 Second-Order Low-Pass Filter

Low-pass filters are commonly employed in signal processing applications to reduce noise and prevent aliasing.

The TLVx365 is designed to construct high-speed, high-precision active filters. Figure 8-5 shows a second-order

low-pass filter commonly encountered in signal processing applications.

+

±

Output

Input

R1

590

R4

2.94 k

R3

499

C2

39 nF

C5

1 nF

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Figure 8-5. Second-Order Low-Pass Filter

8.2.1.1 Design Requirements

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 pass band

8.2.1.2 Detailed Design Procedure

Figure 8-5 shows the infinite-gain, multiple-feedback circuit for a low-pass network function. Use Equation 1 to

calculate the voltage transfer function.

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

(1)

This circuit produces a signal inversion. For this circuit, use Equation 2 to calculate the gain at dc and the

low-pass cutoff frequency.

4

1

C

3

4

2

5

R

Gain

R

1

f

1 R R C C

2S

(2)

8.2.1.3 Application Curve

Frequency (Hz)

-60

-40

-20

0

20

100

1k

10k

100k

1M

Figure 8-6. TLVx365 Second-Order 25 kHz, Chebyshev, Low-Pass Filter

TLV365, TLV2365

SBOSAA8C – DECEMBER 2022 – REVISED AUGUST 2024

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