AD603ARZ Analog Devices Inc, AD603ARZ Datasheet - Page 9

• Manufacturer Part Number: AD603ARZ
• Description: IC AMP VGA 90MHZ LN 50MA 8SOIC
• Manufacturer: Analog Devices Inc
• Series: X-AMP®r
• Type: Var Gain Ampr

Specifications of AD603ARZ

• Amplifier Type: Variable Gain
• Number Of Circuits: 1
• Slew Rate: 275 V/µs
• -3db Bandwidth: 90MHz
• Current - Input Bias: 200nA
• Current - Supply: 12.5mA
• Current - Output / Channel: 50mA
• Voltage - Supply, Single/dual (±): 9.5 V ~ 12.6 V, ±4.75 V ~ 6.3 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• No. Of Amplifiers: 1
• Bandwidth: 90MHz
• Gain Accuracy: 1.5dB
• No. Of Channels: 1
• Supply Voltage Range: ± 4.75V To ± 6.3V
• Amplifier Case Style: SOIC
• No. Of Pins: 8
• Number Of Channels: 1
• Number Of Elements: 2
• Power Supply Requirement: Dual
• Voltage Gain Db: 31.3dB
• Input Resistance: 0.000103@±5VMohm
• Input Bias Current: 0.2@±5VnA
• Single Supply Voltage (typ): Not RequiredV
• Dual Supply Voltage (typ): ±5V
• Power Dissipation: 400mW
• Rail/rail I/o Type: No
• Single Supply Voltage (min): Not RequiredV
• Single Supply Voltage (max): Not RequiredV
• Dual Supply Voltage (min): ±4.75V
• Dual Supply Voltage (max): ±6.3V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 8
• Package Type: SOIC N
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AD603-EVALZ - BOARD EVALUATION FOR AD603
• Output Type: -
• Gain Bandwidth Product: -
• Voltage - Input Offset: -
• Lead Free Status / Rohs Status: Compliant

Optionally, when a resistor is placed from FDBK to COMM,
higher gains can be achieved. This fourth mode is of limited
value because of the low bandwidth and the elevated output off-
sets; it is thus not included in Figure 2.
The gain of this amplifier in the first two modes is set by the
ratio of on-chip laser-trimmed resistors. While the ratio of these
resistors is very accurate, the absolute value of these resistors
can vary by as much as ± 20%. Thus, when an external resistor
is connected in parallel with the nominal 6.44 kW ± 20% inter-
nal resistor, the overall gain accuracy is somewhat poorer. The
worst-case error occurs at about 2 kW (see Figure 4).
While the gain-bandwidth product of the fixed-gain amplifier is
about 4 GHz, the actual bandwidth is not exactly related to the
maximum gain. This is because there is a slight enhancing of the
ac response magnitude on the maximum bandwidth range, due
to higher order poles in the open-loop gain function; this mild
peaking is not present on the higher gain ranges. Figure 2 shows
how optional capacitors may be added to extend the frequency
response in high gain modes.
CASCADING TWO AD603S
Two or more AD603s can be connected in series to achieve
higher gain. Invariably, ac coupling must be used to prevent
the dc offset voltage at the output of each amplifier from
overloading the following amplifier at maximum gain. The
required high-pass coupling network will usually be just a
capacitor, chosen to set the desired corner frequency in
conjunction with the well defined 100 W input resistance of
the following amplifier.
For two AD603s, the total gain-control range becomes 84 dB
(2
will be somewhat reduced. Depending on the pin strapping, the
gain and bandwidth for two cascaded amplifiers can range from
–22 dB to +62 dB (with a bandwidth of about 70 MHz) to
+22 dB to +102 dB (with a bandwidth of about 6 MHz).
REV. E
Figure 4. Worst-Case Gain Error, Assuming Internal
Resistors Have a Maximum Tolerance of –20%
(Top Curve) or +20% (Bottom Curve)
42.14 dB); the overall –3 dB bandwidth of cascaded stages
–0.2
–0.4
–0.6
–0.8
–1.0
1.2
1.0
0.8
0.6
0.4
0.2
0.0
10
100
VdB (OUT) – VdB (O
1k
R
EXT
–1:VdB (OUT) – (–1):VdB (O
( )
REF
10k
)
100k
REF
)
1M
–9–
There are several ways of connecting the gain-control inputs in
cascaded operation. The choice depends on whether it is impor-
tant to achieve the highest possible Instantaneous Signal-to-Noise
Ratio (ISNR), or, alternatively, to minimize the ripple in the gain
error. The following examples feature the AD603 programmed
for maximum bandwidth; the explanations apply to other gain/
bandwidth combinations with appropriate changes to the arrange-
ments for setting the maximum gain.
Sequential Mode (Optimal S/N Ratio)
In the sequential mode of operation, the ISNR is maintained at
its highest level for as much of the gain control range possible.
Figure 5 shows the SNR over a gain range of –22 dB to +62 dB,
assuming an output of 1 V rms and a 1 MHz bandwidth;
Figure 6 shows the general connections to accomplish this.
Here, both the positive gain-control inputs (GPOS) are driven
in parallel by a positive-only, ground-referenced source with a
range of 0 V to +2 V, while the negative gain-control inputs
(GNEG) are biased by stable voltages to provide the needed
gain offsets. These voltages may be provided by resistive divid-
ers operating from a common voltage reference.
The gains are offset (Figure 7) such that A2’s gain is increased
only after A1’s gain has reached its maximum value. Note that
for a differential input of –600 mV or less, the gain of a single
amplifier (A1 or A2) will be at its minimum value of –11.07 dB;
for a differential input of +600 mV or more, the gain will be at
its maximum value of 31.07 dB. Control inputs beyond these
limits will not affect the gain and can be tolerated without dam-
age or foldover in the response. This is an important aspect of
the AD603’s gain-control response. (See the Specifications sec-
tion of this data sheet for more details on the allowable voltage
range.) The gain is now
where V
by the gain range chosen. In the explanatory notes that follow,
we assume the maximum bandwidth connections are used, for
which G
Figure 5. SNR vs. Control Voltage—Sequential Control
(1 MHz Bandwidth)
Gain (dB) = 40 V
O
G
90
85
80
75
70
65
60
55
50
–0.2
is –20 dB.
is the applied control voltage and G
0.2
G
+ G
0.6
O
V
1.0
C
(V)
1.4
O
1.8
is determined
AD603
2.2
(3)