adl5562 Analog Devices, Inc., adl5562 Datasheet - Page 13

• Manufacturer Part Number: adl5562
• Description: 3.3 Ghz Ultralow Distortion Rf/if Differential Amplifier
• Manufacturer: Analog Devices, Inc.

CIRCUIT DESCRIPTION
BASIC STRUCTURE
The ADL5562 is a low noise, fully differential amplifier/ADC
driver that uses a 3.3 V supply. It provides three gain options
(6 dB, 12 dB, and 15.5 dB) without the need for external
resistors and has wide bandwidths of 2.6 GHz for 6 dB, 2.3 GHz
for 12 dB, and 2.1 GHz for 15.5 dB. Input impedance is 400 Ω
differential for 6 dB, 200 Ω for 12 dB, and 133 Ω for 15.5 dB. It
has a differential output impedance of 10 Ω and a common-
mode adjust voltage of 1.25 V to 1.85 V.
The ADL5562 is composed of a fully differential amplifier with
on-chip feedback and feed-forward resistors. The two feed-
forward resistors on each input set this pin-strappable amplifier
in three different gain configurations of 6 dB, 12 dB, and 15.5 dB.
The amplifier is designed to provide high differential open-loop
gain and an output common-mode circuit that enables the user
1
1
/
/
2
2
AC
R
R
S
S
0.1µF
0.1µF
Figure 30. Basic Structure
VIP2
VIP1
VIN1
VIN2
100Ω
200Ω
200Ω
100Ω
400Ω
400Ω
5Ω
5Ω
R
L
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to change the common-mode voltage from a VCOM pin. The
amplifier is designed to provide superior low distortion at
frequencies up 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 80 mA.
The ADL5562 is very flexible in terms of I/O coupling. It can
be ac-coupled or dc-coupled at the inputs and/or the outputs
within the specified input and output common-mode levels.
The input of the device can be configured as single-ended or
differential with similar distortion performance. Due to the
internal connections between the inputs and outputs, the user
should keep the output common-mode voltage between 1.25 V
and 1.85 V for the best distortion. For a dc-coupled input, the
input common mode should be between 1 V and 2.3 V for the
best distortion. The device has been characterized using 2 V p-p
into 200 Ω. If the inputs are ac-coupled, the input and output
common-mode voltages are set by VCC/2 when no external
circuitry is used. The ADL5562 provides an output common-
mode voltage set by VCOM, which allows driving an ADC
directly without external components such as a transformer or
ac-coupling capacitors, provided the VCOM of the amplifier is
within the VCOM of the ADC. For dc-coupled requirements,
the input VCM must be set by the VCOM pin in all three gain
settings.
ADL5562