Data Sheet

ADA4853-1/ADA4853-2/ADA4853-3

APPLICATIONS INFORMATION

SINGLE-SUPPLY VIDEO AMPLIFIER

With low differential gain and phase errors and wide 0.5 dB

flatness, the ADA4853-1/ADA4853-2/ADA4853-3 are ideal

solutions for portable video applications. Figure 51 shows a

typical video driver set for a noninverting gain of +2, where

RF = RG = 1 kΩ. The video amplifier input is terminated into a

shunt 75 Ω resistor. At the output, the amplifier has a series

75 Ω resistor for impedance matching to the video load.

When operating in low voltage, single-supply applications, the

input signal is only limited by the input stage headroom.

75Ω CABLE

VOUT

75Ω

75Ω

VIN

RG

RF

+VS

PD

U1

C1

2.2µF

C2

0.01µF

+

V

Figure 51. Video Amplifier

POWER SUPPLY BYPASSING

Attention must be paid to bypassing the power supply pins of

the ADA4853-1/ADA4853-2/ADA4853-3. High quality capacitors

with low equivalent series resistance (ESR), such as multilayer

ceramic capacitors (MLCCs), should be used to minimize

supply voltage ripple and power dissipation. A large, usually

tantalum, 2.2 µF to 47 µF capacitor located in proximity to the

ADA4853-1

/ADA4853-2/ADA4853-3 is required to provide good

decoupling for lower frequency signals. The actual value is

determined by the circuit transient and frequency requirements.

In addition, 0.1 µF MLCC decoupling capacitors should be

located as close to each of the power supply pins as is physically

possible, no more than ⅛ inch away. The ground returns should

terminate immediately into the ground plane. Locating the bypass

capacitor return close to the load return minimizes ground loops

and improves performance.

LAYOUT

As is the case with all high speed applications, careful attention

to printed circuit board (PCB) layout details prevents associated

board parasitics from becoming problematic. The ADA4853-1/

ADA4853-2

/ADA4853-3 can operate at up to 100 MHz; there-

fore, proper RF design techniques must be employed. The PCB

should have a ground plane covering all unused portions of the

component side of the board to provide a low impedance return

path. Removing the ground plane on all layers from the area

near and under the input and output pins reduces stray capacit-

ance. Signal lines connecting the feedback and gain resistors

should be kept as short as possible to minimize the inductance

and stray capacitance associated with these traces. Termination

resistors and loads should be located as close as possible to their

respective inputs and outputs. Input and output traces should

be kept as far apart as possible to minimize coupling (crosstalk)

through the board. Adherence to microstrip or stripline design

techniques for long signal traces (greater than 1 inch) is

recommended. For more information on high speed board

layout, go to www.analog.com to view A Practical Guide to

High-Speed Printed-Circuit-Board Layout.

Rev. G | Page 17 of 20