Datasheet AD8264 (Analog Devices)

Quad, 235 MHz, DC-Coupled VGA and Differential Output Amplifier Data Sheet AD8264 FEATURES GENERAL DESCRIPTION Low noise
The AD8264 is a quad, linear-in-dB, general-purpose, variable
Voltage noise: 2.3 nV/√Hz
gain amplifier (VGA) with a preamplifier (preamp), and a flexible
Current noise: 2 pA/√Hz
differential output buffer. DC coupling, combined with wide
Wide bandwidth
bandwidth, makes this amplifier a very good pulse processor.
Small signal: 235 MHz (VGAx); 80 MHz (output amplifier)
Each channel includes a single-ended input preamp/VGA section
Large signal: 80 MHz (1 V p-p)
to preserve the wide bandwidth and fast slew rate for low dis-
Gain range
tortion pulse applications. A 6 dB differential output buffer with
0 to 24 dB (input to VGA output)
common-mode and offset adjustments enable direct coupling to
6 to 30 dB (input to differential output)
most modern high speed analog-to-digital converters (ADCs),
Gain scaling: 20 dB/V
using the converter reference output for perfect dc matching levels.
DC-coupled
The −3 dB bandwidth of the preamp/VGA is dc to 235 MHz,
Single-ended input and differential output
and the bandwidth of the differential driver is 80 MHz. The
Supplies: ±2.5 V to ±5 V
floating gain control interface provides a precise linear-in-dB scale
Low power: 140 mW per channel at ±3.3 V
of 20 dB/V and is easy to interface to a variety of external circuits.
APPLICATIONS
The gain of each channel is adjusted independently, and all
Multichannel data acquisition
channels are referenced to a single pin, GNLO. Combined with
Positron emission tomography
a multioutput, digital-to-analog converter (DAC), each section
Gain trim
of the AD8264 can be used for active calibration or as a trim
Industrial and medical ultrasound
amplifier.
Radar receivers
Operation from a bipolar power supply enables amplification of negative voltage pulses generated by current-sinking pulses into a grounded load, such as is typical of photodiodes or photo- multiplier tubes (PMT). Delay-free processing of wideband video signals is also possible.
FUNCTIONAL BLOCK DIAGRAM ONE CHANNEL SHOWN OPPx VGAx PREAMP FIXED GAIN VGA DIFFERENTIAL OUTPUT AMPLIFIER AMPLIFIER 6dB (2×) 6dB (2×) 18dB (8×) IPPx 1kΩ 2kΩ + ATTENUATOR IPNx 100Ω – –24dB TO 0dB 747Ω VOLx 100Ω 107Ω VOHx GAIN INTERPOLATOR VPOS INTERFACE 2kΩ BIAS VNEG 1kΩ
001
COMM GNHx GNLO VOCM OFSx
07736- Figure 1.
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Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE MAXIMUM POWER DISSIPATION ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TEST CIRCUITS THEORY OF OPERATION OVERVIEW PREAMP VGA POST AMPLIFIER VOCM Pin OFSx Pins NOISE APPLICATIONS INFORMATION A LOW CHANNEL COUNT APPLICATION CONCEPT USING A DISCRETE REFERENCE A DC CONNECTED CONCEPT EXAMPLE EVALUATION BOARD CONNECTING AND USING THE AD8264-EVALZ OUTLINE DIMENSIONS ORDERING GUIDE