AD8027ART-R2 datasheet(21/24 Pages) AD

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AD8027/AD8028

Rev. B | Page 21 of 24

Band-Pass Filter

In communication systems, active filters are used extensively in

signal processing. The AD8027/AD8028 is an excellent choice

for active filter applications. In realizing this filter, it is impor-

tant that the amplifier has a large signal bandwidth of at least

10× the center frequency, fO. Otherwise, a phase shift can occur

in the amplifier, causing instability and oscillations.

In the schematic shown in Figure 62, the AD8027/AD8028 is

configured as a 1 MHz band-pass filter. The target specifications

are fO = 1 MHz and a –3 dB pass band of 500 kHz. Start the

design by selecting the following: fO, Q, C1, and R4. Then using

the equations shown below, calculate the remaining variables.

The test data shown in Figure 63 indicates that this design

yielded a filter response with a center frequency fO = 1 MHz and

a bandwidth of 450 kHz.

(MHz)

Band

Pass

k = 2πfOC1

C2 = 0.5C1

R1 = 2/k, R2 = 2/(3k), R3 = 4/k

H = 1/3(6.5 – 1/Q)

R5 = R4/(H – 1)

–5

0.1

µF

0.1

µF

523

Ω

523

Ω

500pF

1000pF

634

Ω

VOUT

316

Ω

105

Ω

VIN

SELECT

AD8027/

AD8028

–

03327-A-061

Figure 62. Band-Pass Filter Schematic

0.1

CH1 S21 LOG

5dB/REF 6.342dB

1:6.3348dB 1.00 000MHz

FREQUENCY – MHz

03327-A-062

Figure 63. Band-Pass Filter Response

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by providing technical support and online design tools. We offer

technical support via free evaluation boards, sample ICs, inter-

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