AD8335_15 Datasheet, PDF (1/28 Pages) Analog Devices – Quad Low Noise, Low Cost Variable Gain Amplifier

Data Sheet
FEATURES
Low noise preamplifier (PrA)
Voltage noise = 1.3 nV/√Hz typical
Current noise = 2.4 pA/√Hz typical
NF = 7 dB (RS = RIN = 50 Ω)
Single-ended input; VIN maximum = 625 mV p-p
Active input match
Input SNR (noise bandwidth = 20 MHz) = 92 dB
VGA
Differential output
VOUT maximum = 5 V p-p, RL = 500 Ω differential
Gain range (8 dB output gain step)
−10 dB to +38 dB—low gain mode
−2 dB to +46 dB—high gain mode
Accurate linear-in-dB gain control
PrA + VGA performance
−3 dB bandwidth of 85 MHz
Excellent overload performance
Supply: 5 V
Power consumption
95 mW/channel (380 mW total)
65 mW/channel (PrA off; 260 mW total)
Power-down
APPLICATIONS
Medical imaging (ultrasound, gamma cameras)
Sonar
Test and measurement
Precise, stable wideband gain control
GENERAL DESCRIPTION
The AD8335 is a quad variable gain amplifier (VGA) with
low noise preamplifier intended for cost and power sensitive
applications. Each channel features a gain range of 48 dB, fully
differential signal paths, active input preamplifier matching,
and user-selectable maximum gains of 46 dB and 38 dB.
Individual gain controls are provided for each channel.
The preamplifier (PrA) has a single-ended to differential gain of
×8 (18.06 dB) and accepts input signals ≤625 mV p-p. PrA noise is
1.2 nV/√Hz and the combined input referred voltage noise of
the PrA and VGA is 1.3 nV/√Hz at maximum gain.
Quad Low Noise, Low Cost
Variable Gain Amplifier
AD8335
FUNCTIONAL BLOCK DIAGRAM
PIP1
PMD1
POP2
PMD2
PIP2
PON2
VCM2
VIP2
VIN2
VIN3
VIP3
VCM3
PON3
PIP3
PMD3
POP3
PMD4
PIP4
18dB
VMD1
18dB
VMD2
AD8335
18dB
VMD3
18dB
VMD4
ATTEN
–48dB TO
0dB
20dB
TO
28dB
VOH1
VOL1
INTERPOLATOR GAIN INT
INTERPOLATOR GAIN INT
ATTEN
–48dB TO
0dB
20dB
TO
28dB
ATTEN
–48dB TO
0dB
20dB
TO
28dB
VGN1
SL12
VGN2
VOL2
VOH2
VOH3
VOL3
INTERPOLATOR GAIN INT
INTERPOLATOR GAIN INT
ATTEN
–48dB TO
0dB
20dB
TO
28dB
VGN3
SL34
VGN4
VOL4
VOH4
Figure 1.
Assuming a 20 MHz noise bandwidth (NBW), the Nyquist
frequency for a 40 MHz ADC, the input SNR is 92 dB. The
HLxx pin optimizes the output SNR for 10-bit and 12-bit
ADCs with 1 V p-p or 2 V p-p full-scale (FS) inputs.
Channel 1 and Channel 2 are enabled through the EN12 pin, and
Channel 3 and Channel 4 are enabled through the EN34 pin.
For VGA only applications, the PrAs can be powered down,
significantly reducing power consumption.
The AD8335 is available in a 64-lead lead frame chip scale
package (9 mm × 9 mm) for the industrial temperature range
of −40°C to +85°C.
Rev. B
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone]
www.analog.com
Fax: [phone] ©2004–2012 Analog Devices, Inc. All rights reserved.