DEMO-MGA-83A datasheet(7/22 Pages) BOARDCOM

7 / 22 page

MGA-83563 Applications Information

The MGA-83563 is two-stage, medium power GaAs RFIC

amplifier designed to be used for driver and output

stages in transmitter applications operating within the

500 MHz to 6 GHz frequency range.

This device is designed for operation in the saturated

mode where it delivers a typical output power of +22

dBm (158 mW) with a power-added efficiency of 37%. The

MGA-83563 has a large signal gain of 18 dB requiring an

input signal level of only +4 dBm to drive it well into satu-

ration. The high output power and high efficiency of the

MGA-83563, combined with +3-volt operation and sub-

miniature packaging, make this device especially useful for

battery-powered, personal communication applications

such as wireless data, cellular phones, and PCS.

The upper end of the frequency range of the MGA-83563

extends to 6 GHz making it a useful solution for medium

power amplifiers in wireless communications products

such as 5.7 GHz spread spectrum or other ISM/license-

free band applications. Internal capacitors on the RFIC

chip limit the low-end frequency response to applica-

tions above approximately 500 MHz.

The thermal limitations of the subminiature SOT-363

(SC-70) package generally restrict the use of the MGA-

83563 to applications that use constant envelope types

of modulation. These types of systems are able to take

full advantage of the MGA-83563’s high efficiency, satu-

rated mode of operation. The use of the MGA-83563 for

linear applications at reduced power levels is discussed

in the “Thermal Design for Reliability” and “Use of the

MGA-83563 for Linear Applications” in this applications

note.

Application Guidelines

The use of the MGA-83563 is very straightforward. The

on-chip, partial RF impedance matching and integrated

bias control circuit simplify the task of using this device.

The design steps consist of (1) selecting an interstage in-

ductor from the data provided, (2) adding provision for

bringing in the DC bias, and (3) designing and optimizing

an output impedance match for the particular frequency

band of interest. The input is already well matched to 50

ohms for most frequencies and in many cases no addi-

tional input matching will be necessary.

Each of the three design steps for using the MGA-83563

will now be discussed in greater detail.

Step 1 — Selecting the Interstage Inductor

The drain of the first stage FET of this two-stage RFIC am-

plifier is connected to package Pin 1. The supply voltage

Vd is connected to this drain through an inductor, L2, as

shown in Figure 18. The supply end of the inductor is by-

passed to ground.

This interstage inductor serves the purpose of complet-

ing the impedance match between the first and second

stages. The value of inductor L2 depends on the particu-

lar frequency for which the MGA-83563 is to be used and

is chosen from the look-up graph in Figure 19.

Input

RFC

Figure 18. Interstage Inductor L2 and Bias Current.

The values for inductor L2 are somewhat dependent on

the specific printed circuit board material, thickness, and

RF layout that are used. The inductor values shown in

Figure 19 have been created for the PCB and RF layout

that is used for the circuit examples presented in this ap-

plication note. The methodology that was used to deter-

mine the optimum values for L2 and for creating Figure

19 is presented in the Appendix. If the user’s PCB and/or

layout differ significantly from the example circuits, refer

to the Appendix for a description of how to determine

the values of L2 for any arbitrary frequency, PCB material,

or RF layout.

Step 2 — Bias Connections

The MGA-83563 is a voltage-biased device and operates

from a single, positive power supply. The supply voltage,

typically +3-volts, must be applied to the drains of both

stages of the RFIC amplifier. The connection to the first

stage drain is made through the interstage inductor, L2,

as described in the previous step. The supply voltage is

applied to the second stage drain through Pin 6, which

is also the RF Output connection. Referring to Figure 18,

an inductor (RFC) is used to separate the RF output signal

from the DC supply. The supply side of the RFC is capaci-

tively bypassed. A DC blocking capacitor is used at the

output to isolate the supply voltage from the succeeding

stage.

DEMO-MGA-83A Arkusz danych(PDF) 7 Page - Broadcom Corporation.

DEMO-MGA-83A Arkusz danych(HTML) 7 Page - Broadcom Corporation.

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Arkusz danych Pobierz

Link URL