AD8335 Datasheet, PDF (1/24 Pages) Analog Devices – Quad Low Noise, Low Cost Variable Gain Amplifier

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 max = 625 mV p-p
Active input match
Input SNR (noise bandwidth = 20 MHz) = 92 dB
VGA
Differential output
VOUT max = 5 V p-p, RL = 500 Ω differential
Gain range (8 dB output gain step)
−10 dB to +38 dB—LO gain mode
−2 dB to +46 dB—HI gain mode
Accurate linear-in-dB gain control
PrA + VGA performance
−3 dB bandwidth of 70 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 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.
Rev. 0
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Specifications subject to change without notice. No license is granted by implication
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Quad Low Noise, Low Cost
Variable Gain Amplifier
AD8335
FUNCTIONAL BLOCK DIAGRAM
61 60
59 58 53 55
52 51 49
PIP1 63
18dB
PMD1 64
VMD1
PMD2 1
18dB
PIP2 2
PON2 4
POP2 5
VIP2 6
VIN2 7
VMD2
VIN3 10
VIP3 11
POP3 12
PON3 13
AD8335
PIP3 15
18dB
PMD3 16
VMD3
PMD4 17
18dB
PIP4 18
VMD4
ATTEN
–48dB TO
0dB
20dB
TO
28dB
47 VOH1
46 VOL1
INTERPOLATOR GAIN INT 56 VGN1
50 SL12
INTERPOLATOR GAIN INT 54 VGN2
ATTEN
–48dB TO
0dB
20dB
TO
28dB
43 VOL2
42 VOH2
ATTEN
–48dB TO
0dB
20dB
TO
28dB
39 VOH3
38 VOL3
INTERPOLATOR GAIN INT 27 VGN3
31 SL34
INTERPOLATOR GAIN INT 25 VGN4
ATTEN
–48dB TO
0dB
20dB
TO
28dB
35 VOL4
34 VOH4
20 21
22 23 28 26
29 30 32
Figure 1.
Assuming a 20 MHz noise bandwidth (NBW), the Nyquist
frequency for a 40 MHz ADC, the input SNR is 92 dB. The
HILO 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.
Channels 1 and 2 are enabled through the EN12 pin while
Channels 3 and 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
(9 mm × 9 mm) package for the industrial temperature range
of −40°C to +85°C.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone]
www.analog.com
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.