herunterladen
AN-1192
APPLICATION NOTE
One Technology Way • P. O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 • www.analog.com
Designing with the AD8338
by David Hunter
Rev. 0 | Page 1 of 12
INTRODUCTION
The low power, high dynamic range AD8338 variable gain
amplifier (VGA) provides many solutions to real-world systems
through the device’s rich feature set. Traditionally, VGAs are
used in many applications, such as signal level normalization,
programmable gain systems, dynamic range extension, and
automatic gain control.
The core of the device gives the user a total dynamic range of
80 dB, which is configured through the GAIN pin. With a
minimalist design, a gain of 1 to 10,000 is achieved in a board
area as small as 18 mm
2
. Upon the application of external
resistors, the part becomes one of the most flexible VGAs on
the market by either offering a lower input noise, a VGA that
can serve as a variable attenuation-to-gain amplifier, or even a
higher total gain amplifier.
This application note describes the design of the AD8338 and
how to use this device in a variety of situations. This includes
general design practices as well as information on how to obtain
particular extended operational modes. Several application
examples are provided.
Figure 1. Block Diagram
INPR
INPD
INMD
INMR
MODECOMM GAIN
FBKM
OUTP
OUTM
DETO VAGC
FBKP
+
–
+
–
VREF
VGA CORE
0dB TO 80dB
OFFSET NULL
OUTPUT
STAGE
0dB
OFSN
VREF
VBAT
AUTOMATIC
GAIN
CONTROL
GAIN INTERFACE
AD8338
11509-001
