ARA2005 datasheet(12/16 Pages) ANADIGICS

12 / 16 page

PRELIMINARY DATA SHEET - Rev 1.3

08/2001

ARA2005

APPLICATION INFORMATION

Transmit Enable / Disable

The ARA2005 includes two amplification stages that

each can be shut down through external control pins

Vg1 and Vg2 (pins 7 and 22, respectively.) By

applying a slightly positive bias of typically +1.0 Volts,

the amplifier is enabled. In order to disable the

amplifier, the control pin needs to be pulled to

ground.

A practical way to implement the necessary control

is to use bias resistor networks similar to those

shown in the test circuit schematic (Figure 4.) Each

network includes a resistor shunted to ground that

serves as a pull-down to disable the amplifier when

no control voltage is applied. When a positive voltage

is applied, the network acts as a voltage divider that

presents the required +1.0 Volts to enable the

amplifier. By selecting different resistor values for

the voltage divider, the network can accommodate

different control voltage inputs.

The Vg1 and Vg2 pins may be connected together

directly, and controlled through a single resistor

network from a common control voltage.

Amplifier Bias Current

The ISET pins (8 and 21) set the bias current for the

amplification stages. Grounding these pins results

in the maximum possible current. By placing a

resistor from the pin to ground, the current can be

reduced. The recommended bias conditions use

the configuration shown in the test circuit schematic

in Figure 4.

Attenuator Control

Each of the four internal attenuation stages of the

ARA2005 is controlled by a TTL-compatible logic input

at one of the attenuator control pins (13 - 16). A logic

high will enable a given attenuator stage, and a logic

low will bypass it.

Output Transformer

Matching the output of the ARA2005 to a 75 Ohm

load is accomplished using a 2:1 turns ratio

transformer. In addition to providing an impedance

transformation, this transformer provides the bias to

the output amplifier stage via the center tap.

The transformer also cancels even mode distortion

products and common mode signals, such as the

voltage transients that occur while enabling and

disabling the amplifiers. As a result, care must be

taken when selecting the transformer to be used at

the output. It must be capable of handling the RF

and DC power requirements without saturating the

core, and it must have adequate isolation and good

phase and amplitude balance. It also must operate

over the desired frequency and temperature range

for the intended application.

ESD Sensitivity

Electrostatic discharges can cause permanent

damage to this device. Electrostatic charges

accumulate on test equipment and the human body,

and can discharge without detection. Although the

ARA2005 has some built-in ESD protection, proper

precautions

and

handling

are

strongly

recommended. Refer to the ANADIGICS application

note on ESD precautions.

ARA2005 Datasheet(PDF) 12 Page - ANADIGICS, Inc

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