Circuit Note

CN-0268

Circuits from the Lab™ reference circuits are engineered and

tested for quick and easysystemintegrationto helpsolve today’s

analog, mixed-signal, and RF design challenges. For more

informationand/orsupport,visitwww.analog.com/CN0268.

Devices Connected/Referenced

ADL5565

6 GHz Ultrahigh Dynamic Range Differential

Amplifier

AD9467

16-Bit, 200 MSPS/250 MSPS ADC

Resonant Approach to Designing a Band-Pass Filter for Narrow-Band, High IF, 16-Bit,

250 MSPS Receiver Front End

Rev. 0

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EVALUATION AND DESIGN SUPPORT

Design and Integration Files

Schematics, Layout Files, Bill of Materials

CIRCUIT FUNCTION AND BENEFITS

The circuit shown in Figure 1 is a 16-bit, 250 MSPS, narrow-band,

high IF receiver front end with an optimum interface between

the ADL5565 differential amplifier and the AD9467 ADC.

The AD9467 is a buffered input 16-bit, 200 MSPS or 250 MSPS

ADC with SNR performance of approximately 75.5 dBFS and

SFDR performance between 95 dBFS and 98 dBFS. The ADL5565

differential amplifier is suitable for driving IF sampling ADCs

because of its high input bandwidth, low distortion, and high

output linearity.

This circuit note describes a systematic procedure for designing

the interface circuit and the antialiasing filter that maintains

high performance and ensures minimal signal loss. A resonant

approach is used to design a maximally flat Butterworth fourth-

order band-pass filter with a center frequency of 200 MHz.

CIRCUIT DESCRIPTION

The advantages of using a differential amplifier to drive a high

speed ADC include signal gain, isolation, and source impedance

matching to the ADC. The ADL5565 allows pin-strappable gain

adjustments of 6 dB, 12 dB, or 15.5 dB. Alternatively, by applying

two external resistors to the inputs, finer gain steps can be achieved

within the 0 dB to 15.5 dB range. Additionally, the ADL5565

offers high output linearity, low distortion, low noise, and wide

input bandwidth. The 3 dB bandwidth is 6 GHz, and the 0.1 dB

flatness is 1 GHz. The ADL5565 is capable of achieving an

output third-order intercept (OIP3) of greater than 50 dB.

0.1µF

ADL5565

G = 6dB

3.5pF

530Ω

0.1µF

33Ω

33Ω

1nF

1nF

XFMR

1:1 Z

ECT1-1-13M

INPUT

Z = 50Ω

INTERNAL

INPUT Z

AD9467

16-BIT

250MSPS

ADC

15Ω

15Ω

310Ω

5.6Ω

5.6Ω

39nH

2pF

VIP2

VIN2

5Ω

5Ω

+3.3V

+1.8V

VIP1

VIN1

+3.3V

FS = 2V p-p DIFF

8.2pF

39nH

150nH

150nH

180nH

Figure 1. Resonant Filter Design for Narrow Band High IF Applications Using the ADL5565 Differential Amplifier and the AD9467 ADC