OPA828 datasheet(29/47 Pages) TI

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8.2.2 Low-Pass Filter

Output

Input

590

2.94 k

499

39 nF

1 nF

Figure 8-5. Typical OPA828 Application Schematic

8.2.2.1 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

8.2.2.2 Detailed Design Procedure

Figure 8-5 shows the infinite-gain multiple-feedback circuit for a low-pass network function. Equation 5 calculates

the voltage transfer function.

OutputInputs =

−1/ R1R3C2C5

s2+ s/C2 1/R1+1/R3+1/R4 +1/R3R4C2C5

(5)

This circuit produces a signal inversion. For this circuit, Equation 6 calculates the gain at dc and the low-pass

cutoff frequency:

Gain=R4R1

fc= 12π 1/R3R4C2C5

(6)

8.2.2.3 Application Curve

Frequency (Hz)

-60

-40

-20

100

10k

100k

Figure 8-6. Low-Pass Filter Transfer Function

8.3 Power Supply Recommendations

The OPAx828 are specified to operate from 8 V to 36 V (±4 V to ±18 V); many specifications apply from –40°C

to +125°C. Parameters that can exhibit significant variance with regard to operating voltage or temperature are

presented in the typical characteristic curves.

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OPA828, OPA2828

SBOS671D – SEPTEMBER 2018 – REVISED DECEMBER 2022

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