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PDF AD8338 Data sheet ( Hoja de datos )
| Número de pieza | AD8338 | |
| Descripción | 18MHz Variable Gain Amplifier | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Data Sheet
Low Power, 18 MHz Variable Gain Amplifier
AD8338
FEATURES
Voltage controlled gain range of 0 dB to 80 dB
3 mA supply current at gain of 40 dB
Low frequency (LF) to 18 MHz operation
Supply range: 3.0 V to 5.0 V
Low noise: 4.5 nV/√Hz at 80 dB gain
Fully differential signal path
Offset correction (offset null) feature
Internal 1.5 V reference
16-lead LFCSP
Automatic gain control feature
Wide gain range for high dynamic range signals
APPLICATIONS
Front end for inductive telemetry systems
Ultrasonic signal receivers
Signal compression for driving an ADC
AGC amplifiers
INPR
INMR
INPD
INMD
FUNCTIONAL BLOCK DIAGRAM
VBAT OFSN VREF
OFFSET NULL
VGA CORE
+
–
0dB TO 80dB
GAIN INTERFACE
AD8338
+
OUTPUT
STAGE
0dB
–
VREF
AUTOMATIC
GAIN
CONTROL
FBKP
OUTP
OUTM
FBKM
COMM
MODE GAIN DETO
Figure 1.
VAGC
GENERAL DESCRIPTION
The AD8338 is a variable gain amplifier (VGA) for applications
that require a fully differential signal path, low power, low noise,
and a well-defined gain over frequency. Although the inputs are
differential, the device can also be driven with a single-ended
source if required.
The basic gain function is linear-in-dB and is controlled by the
voltage applied to Pin GAIN. The nominal gain range spans
from 0 dB to 80 dB for control voltages between 0.1 V to 1.1 V
with a slope of 12.5 mV/dB. The nominal gain range can be
shifted up or down via direct access to Pin INPD and Pin INMD,
the current inputs of the VGA. For example, driving the INPD
and INMD pins with 50 Ω resistors shifts the gain range up by
20 dB, that is, 20 dB to 100 dB, and lowers the input referred
noise of the device to 1.5 nV/√Hz. Additionally, the gain slope
can be inverted via logic Pin MODE.
The AD8338 includes additional circuit blocks to enable input
offset correction and automatic gain control (AGC). DC offset
voltages are removed by the offset correction circuit, which
behaves like a high-pass filter whose corner is set with an external
capacitor. The AGC function varies the gain of the AD8338 to
maintain a constant rms output voltage. An externally applied
voltage to Pin VAGC with respect to the voltage at Pin VREF
sets the output rms amplitude. A capacitor from Pin DETO to
ground sets the response time of the AGC circuit.
100
80
60
40
20
0
VGAIN = 1.1V
VGAIN = 1.0V
VGAIN = 0.9V
VGAIN = 0.8V
VGAIN = 0.7V
VGAIN = 0.6V
VGAIN = 0.5V
VGAIN = 0.4V
VGAIN = 0.3V
VGAIN = 0.2V
VGAIN = 0.1V
–20
–40
10k
100k 1M 10M
FREQUENCY (Hz)
Figure 2. Gain vs. Frequency
100M
The AD8338 offers additional versatility by providing access to
the internal summing nodes of the VGA core and the output
amplifiers. With the addition of a few external passive components,
users can customize the gain, bandwidth, input impedance, and
noise profile of the device to fit their application.
The AD8338 uses a single-supply voltage of 3.0 V to 5.0 V and
is very power efficient, consuming as little as 3 mA quiescent
current at mid gain. The AD8338 is available in a 3 mm × 3 mm,
RoHS-compliant, 16-lead LFCSP and is specified over the
industrial temperature range of −40°C to +85°C.
Rev. B
Document Feedback
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibilityisassumedbyAnalogDevices for itsuse,nor foranyinfringementsofpatentsor 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.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2013–2016 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 page  
AD8338
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
VBAT to COMM
INPR, INPD, INMD, INMR, MODE, GAIN,
FBKM, FBKP, OUTM, OUTP, VAGC,
VREF, OFSN
Operating Temperature Range
Storage Temperature Range
Maximum Junction Temperature
Lead Temperature (Soldering, 10 sec)
Rating
−0.3 V to +5.5 V
COMM to VBAT
−40°C to +85°C
−65°C to +150°C
150°C
300°C
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
Data Sheet
THERMAL RESISTANCE
Table 3. Thermal Resistance
Package Type
θJA
16-Lead LFCSP
48.75
ESD CAUTION
Unit
°C/W
Rev. B | Page 4 of 19
5 Page 
AD8338
2.0
VOUT = 2V p-p
1.5
f = 1MHz
GAIN = 40dB
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
0
0.2 0.4 0.6
TIME (µs)
0.8
Figure 28. Large Signal Pulse Response vs. Time, VGAIN = 0.6 V
100
80
60
CCLL
=
=
0pF
10pF
CCLL
=
=
20pF
47pF
40
20
0
–20
–40
–60
–80
VOUT = 100mV p-p
f = 1.5MHz
GAIN = 1
–100
0 0.2
0.4
TIME (µs)
0.6
0.8
Figure 29. Small Signal Pulse Response vs. Time for Varying Capacitive Loads
VGAIN
0.6
0.1
1.0
0
–1.0
VOUT
0 1 2 3 4 5 6 7 8 9 10
TIME (µs)
Figure 30. Gain Step Response vs. Time
Data Sheet
1.5 f = 100kHz
VIN LOW = 2mV
1.0
VIN HIGH = 20mV
GAIN = 40dB
0.5
0
–0.5
–1.0
–1.5
0
20 40 60 80 100 120 140 160 180 200
TIME (µs)
Figure 31. Overdrive Recovery vs. Time
12
–40°C, MODE PIN HIGH
+25°C, MODE PIN HIGH
10 +85°C, MODE PIN HIGH
–40°C, MODE PIN LOW
+25°C, MODE PIN LOW
8 +85°C, MODE PIN LOW
6
4
2
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
VGAIN (V)
Figure 32. Supply Current vs. VGAIN
50
OFFSET NULL OFF
40
30 10µF
1µF
20
0.1µF
10
0.01µF
0
–10
–20
–30
–40
20 100
GAIN = 100
1k 10k 100k 1M 10M 100M
FREQUENCY (Hz)
Figure 33. Offset Null Bandwidth vs. Offset Null Capacitor
Rev. B | Page 10 of 19
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet AD8338.PDF ] | |
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