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AD604AR 参数 Datasheet PDF下载

AD604AR图片预览
型号: AD604AR
PDF下载: 下载PDF文件 查看货源
内容描述: 双通道,超低噪声可变增益放大器 [Dual, Ultralow Noise Variable Gain Amplifier]
分类和应用: 模拟IC信号电路放大器光电二极管
文件页数/大小: 20 页 / 499 K
品牌: AD [ ANALOG DEVICES ]
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a
FEATURES
Ultralow Input Noise at Maximum Gain:
0.80 nV/√Hz, 3.0 pA/√Hz
Two Independent Linear-in-dB Channels
Absolute Gain Range per Channel Programmable:
0 dB to +48 dB (Preamp Gain = +14 dB), through
+6 dB to +54 dB (Preamp Gain = +20 dB)
1.0 dB Gain Accuracy
Bandwidth: 40 MHz (–3 dB)
300 k Input Resistance
Variable Gain Scaling: 20 dB/V through 40 dB/V
Stable Gain with Temperature and Supply Variations
Single-Ended Unipolar Gain Control
Power Shutdown at Lower End of Gain Control
Can Drive A/D Converters Directly
APPLICATIONS
Ultrasound and Sonar Time-Gain Control
High Performance AGC Systems
Signal Measurement
Dual, Ultralow Noise
Variable Gain Amplifier
AD604
FUNCTIONAL BLOCK DIAGRAM
PAO
–DSX
+DSX
VGN
GAIN CONTROL
AND SCALING
DIFFERENTIAL
ATTENUATOR
R-1.5R
LADDER NETWORK
0 TO –48.4dB
VOCM
PROGRAMMABLE
ULTRALOW NOISE
PREAMPLIFIER
G = 14–20dB
PRECISION PASSIVE
INPUT ATTENUATOR
VREF
PAI
AFA
OUT
FIXED GAIN
AMPLIFIER
+34.4dB
PRODUCT DESCRIPTION
The AD604 is an ultralow noise, very accurate, dual channel,
linear-in-dB variable gain amplifier (VGA) optimized for time-
based variable gain control in ultrasound applications; however
it will support any application requiring low noise, wide bandwidth
variable gain control. Each channel of the AD604 provides a
300 kΩ input resistance and unipolar gain control for ease of
use. User determined gain ranges, gain scaling (dB/V) and dc
level shifting of output further optimize application performance.
Each channel of the AD604 utilizes a high performance pre-
amplifier that provides an input referred noise voltage of
0.8 nV/√Hz. The very accurate linear-in-dB response of the
AD604 is achieved with the differential input exponential amplifier
(DSX-AMP) architecture. Each of the DSX-AMPs comprise a
variable attenuator of 0 dB to 48.36 dB followed by a high speed
fixed gain amplifier. The attenuator is based on a seven stage
R-1.5R ladder network. The attenuation between tap points
is 6.908 dB and 48.36 dB for the ladder network.
Each independent channel of the AD604 provides a gain range
of 48 dB which can be optimized for the application by program-
ming the preamplifier with a single external resistor in the
preamp feedback path. The linear-in-dB gain response of the
AD604 can be described by the equation:
G
(dB) = (Gain
Scaling
(dB/V )
×
VGN
(V )) + (Preamp
Gain
(dB) – 19
dB).
Preamplifier gains between 5 and 10 (+14 dB and +20 dB)
provide overall gain ranges per channel of 0 dB through +48 dB
and +6 dB through +54 dB. The two channels of the AD604
can be cascaded to provide greater levels of gain range by bypass-
ing the 2nd channel’s preamplifier. However, in multiple channel
systems, cascading the AD604 with other devices in the AD60x
VGA family, which do not include a preamplifier may provide
a more efficient solution. The AD604 provides access to the
output of the preamplifier allowing for external filtering be-
tween the preamplifier and the differential attenuator stage.
The gain control interface provides an input resistance of
approximately 2 MΩ and scale factors from 20 dB/V to
30 dB/V for a V
REF
input voltage of 2.5 V to 1.67 V respect-
ively. Note that scale factors up to 40 dB/V are achievable
with reduced accuracy for scales above 30 dB/V. The gain scales
linear-in-dB with control voltages of 0.4 V to 2.4 V with the
20 dB/V scale. Below and above this gain control range, the gain
begins to deviate from the ideal linear-in-dB control law. The
gain control region below 0.1 V is not used for gain control. In
fact when the gain control voltage is <50 mV the amplifier
channel is powered down to 1.9 mA.
The AD604 is available in a 24-pin plastic SSOP, SOIC and DIP,
and is guaranteed for operation over the –40°C to +85°C
temperature range.
REV. 0
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
World Wide Web Site: http://www.analog.com
Fax: 617/326-8703
© Analog Devices, Inc., 1996