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ADL5566

Data Sheet

Rev. C | Page 14 of 24

CIRCUIT DESCRIPTION

The ADL5566 is a high gain, fully differential dual amplifier/ADC

driver that uses a 2.8 V to 5 V supply. It provides a 16 dB gain

that can be reduced by adding external series resistors. The 3 dB

bandwidth is 4.5 GHz, and it has a differential input impedance of

160 Ω. It has a differential output impedance of 10 Ω and an

output common-mode adjust voltage of 1.1 V to 1.8 V.

5Ω

80Ω

500Ω

80Ω

½ RS

0.1µF

–

ADL5566

Figure 35. Basic Structure

The ADL5566 is composed of a dual fully differential amplifier

with on-chip feedback and feed-forward resistors. The gain is fixed

at 16 dB but can be reduced by adding two resistors in series with

the two inputs (see the Gain Adjustment and Interfacing section).

The amplifier is designed to provide a high differential open-loop

gain and has an output common-mode circuit that enables the

user to change the output common-mode voltage by applying a

voltage to a VCOMx pin. The amplifier is designed to provide

superior low distortion at frequencies to and beyond 300 MHz

with low noise and low power consumption. The low distortion

and noise are realized with a 3.3 V power supply at 140 mA.

The dual amplifier has an extremely high gain bandwidth (GBW)

product that results in distortion levels that are the best in the

industry for power consumed at frequencies beyond 100 MHz.

This amplifier achieves greater than −69 dBc IMD3 at 500 MHz

and −100 dBc at 200 MHz for 2 V p-p operation. In addition,

the ADL5566 can also deliver 5 V p-p operation under heavy

loads. The internal gain is set at 16 dB, and the part has a noise

figure of 6.5 dB and a RTI of 1.5 nV/√Hz. When comparing noise

figure and distortion performance, this amplifier delivers the

best in category spurious-free dynamic range (SFDR).

The ADL5566 is very flexible in terms of I/O coupling. It can be

ac- or dc-coupled. For dc coupling, the output common-mode

voltage (VCOMx) can be adjusted (using the VCOMx pin) from

1.1 V to 1.8 V output for VCCx at 3.3 V and up to 3 V with VCCx

at 5 V. For the best distortion, the common-mode output should

not go below 1.25 V at VCCx equal to 3.3 V and 1.35 V for 5 V

VCCx operation. Note that the input common-mode voltage

slaves to the VCOMx output voltage when ac-coupled at the

inputs. For dc-coupled inputs, the input common-mode voltage

should also stay between 1.25 V and 1.8 V for a 3.3 V supply and

1.35 V to 3.5 V for a 5 V supply. Note again that, for ac-coupled

applications with series capacitors at the inputs, as in Figure 37,

the output common-mode voltage, VCOMx, sets the common-

mode input to the same level. Because of the wide input common-

mode range, this part can easily be dc-coupled to many types of

mixers, demodulators, and amplifiers. Forcing a higher input

VCOMx does not affect the output VCOMx in dc-coupled mode.

Note that, if the outputs are ac-coupled (see the ADC Interfacing

section), no external VCOMx adjust is required because the

amplifier common-mode outputs are set at VCCx/2.

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