General-Purpose, Low Cost,

DC-Coupled VGA

AD8337

Rev. B

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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

FUNCTIONAL BLOCK DIAGRAM

VOUT

GAIN

INPP

2

3

5

PRAO

1

INPN

VCOM

+

–

7

AD8337

8 SECTIONS

6

VNEG

VPOS

8

GAIN CONTROL

INTERFACE

8

18dB

PREAMP

(PRA)

4

Figure 1.

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.

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.