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Data Sheet
FEATURES
Linear-in-dB gain control
Pin-programmable gain ranges
−11 dB to +31 dB with 90 MHz bandwidth
9 dB to 51 dB with 9 MHz bandwidth
Any intermediate range, for example −1 dB to +41 dB
with 30 MHz bandwidth
Bandwidth independent of variable gain
1.3 nV/√Hz input noise spectral density
±0.5 dB typical gain accuracy
Low Noise, 90 MHz
Variable Gain Amplifier
AD603
The decibel gain is linear in dB, accurately calibrated, and stable
over temperature and supply. The gain is controlled at a high
impedance (50 MΩ), low bias (200 nA) differential input; the
scaling is 25 mV/dB, requiring a gain control voltage of only
1 V to span the central 40 dB of the gain range. An overrange
and underrange of 1 dB is provided whatever the selected range.
The gain control response time is less than 1 μs for a 40 dB change.
The differential gain control interface allows the use of either
differential or single-ended positive or negative control voltages.
Several of these amplifiers may be cascaded and their gain
control gains offset to optimize the system SNR.
The AD603 can drive a load impedance as low as 100 Ω with
low distortion. For a 500 Ω load in shunt with 5 pF, the total
harmonic distortion for a ±1 V sinusoidal output at 10 MHz is
typically −60 dBc. The peak specified output is ±2.5 V minimum
into a 500 Ω load.
The AD603 uses a patented proprietary circuit topology—the
X-AMP®. The X-AMP comprises a variable attenuator of 0 dB
to −42.14 dB followed by a fixed-gain amplifier. Because of the
attenuator, the amplifier never has to cope with large inputs and
can use negative feedback to define its (fixed) gain and dynamic
performance. The attenuator has an input resistance of 100 Ω,
laser trimmed to ±3%, and comprises a 7-stage R-2R ladder
network, resulting in an attenuation between tap points of
6.021 dB. A proprietary interpolation technique provides a
continuous gain control function that is linear in dB.
The AD603 is specified for operation from −40°C to +85°C.
APPLICATIONS
RF/IF AGC amplifiers
Video gain controls
A/D range extensions
Signal measurements
GENERAL DESCRIPTION
The AD603 is a low noise, voltage-controlled amplifier for use
in RF and IF AGC systems. It provides accurate, pin-selectable
gains of −11 dB to +31 dB with a bandwidth of 90 MHz or +9 dB to
51+ dB with a bandwidth of 9 MHz. Any intermediate gain
range may be arranged using one external resistor. The input
referred noise spectral density is only 1.3 nV/√Hz, and power
consumption is 125 mW at the recommended ±5 V supplies.
FUNCTIONAL BLOCK DIAGRAM
SCALING
REFERENCE
GPOS
GNEG
V
G
GAIN-
CONTROL
INTERFACE
PRECISION PASSIVE
INPUT ATTENUATOR
FIXED-GAIN
AMPLIFIER
VOUT
AD603
6.44kΩ*
FDBK
694Ω*
0dB
VINP
R
–6.02dB
R
–12.04dB –18.06dB –24.08dB
R
R
R
–30.1dB
R
–36.12dB –42.14dB
R
20Ω*
2R
2R
2R
2R
2R
2R
R
COMM
R-2R LADDER NETWORK
*NOMINAL VALUES.
00539-001
Figure 1.
Rev.
K
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: 781.329.4700
www.analog.com
Fax: 781.461.3113
©1993–2012 Analog Devices, Inc. All rights reserved.
AD603
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 4
ESD Caution .................................................................................. 4
Pin Configurations and Function Descriptions ........................... 5
Typical Performance Characteristics ............................................. 6
Test Circuits ..................................................................................... 11
Theory of Operation ...................................................................... 12
Noise Performance ..................................................................... 12
Data Sheet
The Gain Control Interface ....................................................... 13
Programming the Fixed-Gain Amplifier Using Pin
Strapping...................................................................................... 13
Using the AD603 in Cascade ........................................................ 15
Sequential Mode (Optimal SNR) ............................................. 15
Parallel Mode (Simplest Gain Control Interface) .................. 16
Low Gain Ripple Mode (Minimum Gain Error) ................... 17
Applications Information .............................................................. 18
A Low Noise AGC Amplifier .................................................... 18
Caution ........................................................................................ 19
Evaluation Board ............................................................................ 20
Outline Dimensions ....................................................................... 22
Ordering Guide .......................................................................... 23
REVISION HISTORY
4/12—Rev. J to Rev. K
Changes to Table 1 ............................................................................ 3
Added Figure 10 and Figure 11; Renumbered Sequentially ....... 7
Added Test Circuits Section .......................................................... 11
Moved Figure 29 and Figure 30 .................................................... 11
12/11—Rev. I to Rev. J
Changes to Figure 1 ......................................................................... 1
Changes to Evaluation Board Section .......................................... 19
Changes to Figure 48 Through Figure 50 .................................... 19
Changes to Figure 51 Through Figure 54 .................................... 20
Added Figure 57.............................................................................. 22
5/07—Rev. G to Rev. H
Changes to Layout .......................................................................... 14
Changes to Layout .......................................................................... 15
Changes to Layout .......................................................................... 16
Inserted Evaluation Board Section, and Figure 48 to
Figure 51 .......................................................................................... 19
Inserted Figure 52 and Table 4 ...................................................... 20
Changes to Ordering Guide .......................................................... 21
3/05—Rev. F to Rev. G
Updated Format .................................................................. Universal
Change to Features ............................................................................1
Changes to General Description .....................................................1
Change to Figure 1 ............................................................................1
Changes to Specifications .................................................................3
New Figure 4 and Renumbering Subsequent Figures ..................6
Change to Figure 10 ..........................................................................7
Change to Figure 23 ..........................................................................9
Change to Figure 29 ....................................................................... 12
Updated Outline Dimensions ....................................................... 20
4/04—Rev. E to Rev. F
Changes to Specifications .................................................................2
Changes to Ordering Guide .............................................................3
8/03—Rev. D to Rev E
Updated Format .................................................................. Universal
Changes to Specifications .................................................................2
Changes to TPCs 2, 3, 4 ....................................................................4
Changes to Sequential Mode (Optimal S/N Ratio) section .........9
Change to Figure 8 ......................................................................... 10
Updated Outline Dimensions ....................................................... 14
Rev. K | Page 2 of 24
Data Sheet
SPECIFICATIONS
AD603
@ T
A
= 25°C, V
S
= ±5 V, –500 mV ≤ V
G
≤ +500 mV, GNEG = 0 V, –10 dB to +30 dB gain range, R
L
= 500 Ω, and C
L
= 5 pF, unless
otherwise noted.
Table 1.
Parameter
INPUT CHARACTERISTICS
Input Resistance
Input Capacitance
Input Noise Spectral Density
1
Noise Figure
1 dB Compression Point
Peak Input Voltage
OUTPUT CHARACTERISTICS
−3 dB Bandwidth
Slew Rate
Peak Output
2
Output Impedance
Output Short-Circuit Current
Group Delay Change vs. Gain
Group Delay Change vs. Frequency
Differential Gain
Differential Phase
Total Harmonic Distortion
Third-Order Intercept
ACCURACY
Gain Accuracy, f = 100 kHz; Gain (dB) = (40 V
G
+ 10) dB
T
MIN
to T
MAX
Gain, f = 10.7 MHz
Output Offset Voltage
3
T
MIN
to T
MAX
Output Offset Variation vs. V
G
T
MIN
to T
MAX
GAIN CONTROL INTERFACE
Gain Scaling Factor
T
MIN
to T
MAX
GNEG, GPOS Voltage Range
Input Bias Current
Input Offset Current
Differential Input Resistance
Response Rate
POWER SUPPLY
Specified Operating Range
Quiescent Current
T
MIN
to T
MAX
1
Conditions
Pin 3 to Pin 4
Input short-circuited
f = 10 MHz, gain = maximum, R
S
= 10 Ω
f = 10 MHz, gain = maximum, R
S
= 10 Ω
V
OUT
= 100 mV rms
R
L
≥ 500 Ω
R
L
≥ 500 Ω
f ≤ 10 MHz
f = 3 MHz; full gain range
V
G
= 0 V; f = 1 MHz to 10 MHz
f = 10 MHz, V
OUT
= 1 V rms
f = 40 MHz, gain = maximum, R
S
= 50 Ω
−500 mV ≤ V
G
≤ +500 mV
V
G
= -0.5 V
V
G
= 0.0 V
V
G
= 0.5 V
V
G
= 0 V
−500 mV ≤ V
G
≤ +500 mV
100 kHz
10.7 MHz
Min
97
Typ
100
2
1.3
8.8
−11
±1.4
90
275
±3.0
2
50
±2
±2
0.2
0.2
−60
15
±0.5
−9.0
+10.5
+30.3
Max
103
Unit
Ω
pF
nV/√Hz
dB
dBm
V
MHz
V/µs
V
Ω
mA
ns
ns
%
Degree
dBc
dBm
±2
±2.5
−1
−1.5
−10.3
+9.5
+29.3
+1
+1.5
−8.0
+11.5
+31.3
20
30
20
30
40.6
42
39.9
+2.0
250
dB
dB
dB
dB
dB
mV
mV
mV
mV
dB/V
dB/V
dB/V
V
nA
nA
MΩ
dB/µs
V
mA
mA
4
39.4
38
38.7
−1.2
50
40
39.3
100
10
50
80
12.5
Pin 1 to Pin 2
Full 40 dB gain change
±4.75
±6.3
17
20
Typical open or short-circuited input; noise is lower when system is set to maximum gain and input is short-circuited. This figure includes the effects of both voltage
and current noise sources.
2
Using resistive loads of 500 Ω or greater or with the addition of a 1 kΩ pull-down resistor when driving lower loads.
3
The dc gain of the main amplifier in the AD603 is ×35.7; therefore, an input offset of 100 µV becomes a 3.57 mV output offset.
4
GNEG and GPOS, gain control, and voltage range are guaranteed to be within the range of −V
S
+ 4.2 V to +V
S
− 3.4 V over the full temperature range of −40°C to +85°C.
Rev. K | Page 3 of 24
AD603
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Supply Voltage ±V
S
Internal Voltage VINP (Pin 3)
GPOS, GNEG (Pin 1 and Pin2)
Internal Power Dissipation
Operating Temperature Range
AD603A
AD603S
Storage Temperature Range
Lead Temperature (Soldering, 60 sec)
Rating
±7.5 V
±2 V Continuous
±V
S
for 10 ms
±V
S
400 mW
−40°C to +85°C
−55°C to +125°C
−65°C to +150°C
300°C
Data Sheet
Table 3. Thermal Characteristics
Package Type
8-Lead SOIC
8-Lead CERDIP
θ
JA
155
140
θ
JC
33
15
Unit
°C/W
°C/W
ESD CAUTION
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
Rev. K | Page 4 of 24
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