AD8337_07 Datasheet, PDF (1/24 Pages) Analog Devices – General-Purpose, Low Cost, DC-Coupled VGA

FEATURES
Low noise
Voltage noise = 2.2 nV/√Hz
Current noise = 4.8 pA/√Hz (positive input)
Wide bandwidth (−3 dB) = 280 MHz
Nominal gain range: 0 dB to 24 dB (preamp gain = 6 dB)
Gain scaling: 19.7 dB/V
DC-coupled
Single-ended input and output
High speed uncommitted op amp input
Supplies: +5 V, ±2.5 V, or ±5 V
Low power: 78 mW with ±2.5 V supplies
APPLICATIONS
Gain trim
PET scanners
High performance AGC systems
I/Q signal processing
Video
Industrial and medical ultrasound
Radar receivers
GENERAL DESCRIPTION
The AD8337 is a low noise, single-ended, linear-in-dB, general-
purpose variable gain amplifier (VGA) usable at frequencies
from dc to 100 MHz; the −3 dB bandwidth is 280 MHz.
Excellent bandwidth uniformity across the entire gain range
and low output-referred noise makes the AD8337 ideal for
gain trim applications and for driving high speed analog-to-
digital converters (ADCs).
Excellent dc characteristics combined with high speed make
the AD8337 particularly suited for industrial ultrasound, PET
scanners, and video applications. Dual-supply operation enables
gain control of negative-going pulses such as generated by
photodiodes or photomultiplier tubes.
The AD8337 uses the popular and versatile X-AMP® architecture,
exclusively from Analog Devices, Inc., with a gain range of 24 dB.
The gain control interface provides precise linear-in-dB scaling
of 19.7 dB/V, referenced to VCOM.
General-Purpose, Low Cost,
DC-Coupled VGA
AD8337
FUNCTIONAL BLOCK DIAGRAM
VPOS
8
AD8337
GAIN 7
GAIN CONTROL
INTERFACE
18dB
1 VOUT
INPP 3
PREAMP
(PRA)
+
INPN 4 ^–
VCOM 2
5
PRAO
8 SECTIONS
6
VNEG
Figure 1.
The AD8337 includes an uncommitted operational current-
feedback preamplifier (PrA) that operates in inverting or
noninverting configurations. Using external resistors, the
device can be configured for gains of 6 dB or greater. The
AD8337 is characterized by a noninverting PrA gain of 2× using
two external 100 Ω resistors. The attenuator has a range of
24 dB, and the output amplifier has a fixed gain of 8× (18.06 dB).
The lowest nominal gain range is 0 dB to 24 dB and can
be shifted up or down by adjusting the preamp gain. Multiple
AD8337s can be connected in series for larger gain ranges, and
for interstage filtering to suppress noise and distortion, and for
nulling offset voltages.
The operating temperature range is –40°C to +85°C, and it is
available in an 8-lead, 3 mm × 3 mm LFCSP.
Rev. B
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