ADL5565 AD [Analog Devices], ADL5565 Datasheet - Page 19

• Manufacturer Part Number: ADL5565
• Description: 6 GHz Ultrahigh Dynamic Range Differential Amplifier
• Manufacturer: AD [Analog Devices]

The single-ended gain can be determined using the following
formula. The values of R
are shown in Table 8.
In Equation 2, R
Table 8. Values of R
Gain (dB)
5.3
10.3
13
1
2
GAIN ADJUSTMENT AND INTERFACING
The effective gain of the
of techniques. A matched attenuator network can reduce the
effective gain; however, this requires the addition of a separate
component that can be prohibitive in size and cost. Instead, a
simple voltage divider can be implemented using the combination
of additional series resistors at the amplifier input and the input
impedance of the ADL5565, as shown in Figure 36. A pair of
resistors is used to match to the impedance of the previous stage.
Figure 36 shows a typical implementation of the divider concept
that effectively reduces the gain by adding attenuation at the
input. For frequencies less than 100 MHz, the input impedance
of the
resistance (differential) for maximum, middle, and minimum
gains, respectively. Assuming that the frequency is low enough
to ignore the shunt reactance of the input and high enough so
that the reactance of moderately sized ac coupling capacitors
can be considered negligible, the insertion loss, Il, due to the
shunt divider can be expressed as
In Equation 3, R
R
These values are based on a 50 Ω input match.
G
is the gain setting resistor (see Figure 1).
1
1
/
/
AC
2
2
Adjusted Gain (dB) =
6 dB, 12 dB, or 15.5 dB Gain – Il (dB)
A
Il
R
R
ADL5565
S
S
(
V
dB
1
=
)
Figure 36. Gain Adjustment Using a Series Resistor
=
R
1
1
20
/
/
G
2
2
R
R
+
log
G
SHUNT
SHUNT
G
can be modeled as a real 66 Ω, 100 Ω, or 200 Ω
⎛
⎜
⎜
⎝
is the gain setting resistor (see Figure 1).
is the gain setting resistor (see Figure 1).
200
R
⎛
⎜
⎜
⎝
R
S
R
S
G
×
+
SERIES
and R
ADL5565
R
R
G
R
100
50
33.5
R
2
0.1 µF
0.1µF
2
and R
G
G
⎞
⎟
⎟
⎠
+
(Ω)
×
X
R
for Single-Ended Gain
1
1
R
1
/
/
G
2
2
X
S
R
R
⎞
⎟
⎟
⎠
R
can be reduced using a number
for each gain configuration
+
SERIES
SERIES
2
R
2
×
R
VIN1
VIN2
X
VIP1
VIP2
R
+
X
R
R2 || 158
R2 || 96
R2 || 74
R
X
ADL5565
S
(Ω)
×
10
2
2
R
+
2
L
R
L
Rev. 0 | Page 19 of 28
(2)
(3)
(4)
The necessary shunt component, R
impedance, R
In Equation 5, R
The insertion loss and the resultant power gain for multiple
shunt resistor values are summarized in Table 9. The source
resistance and input impedance need careful attention when
using Equation 3, Equation 4, and Equation 5. The reactance
of the input impedance of the
capacitors must be considered before assuming that they make
a negligible contribution.
Table 9. Differential Gain Adjustment Using Series Resistor
Gain
(dB)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15.5
1
2
3
4
5
Amplifier is configured for 6 dB gain setting.
Amplifier is configured for 12 dB gain setting.
Amplifier is configured for 15.5 dB gain setting.
R
The resistor values are rounded to the nearest real resistor value.
1
1
1
1
1
1
1
2
2
2
G
2
2
2
3
3
is the gain setting resistor (see Figure 1).
3
R
SHUNT
Differential
R
200
200
200
200
200
200
200
100
100
100
100
100
100
66.7
66.7
66.7
G
(Ω)
=
S
, can be expressed as
4
R
1
G
S
is the gain setting resistor (see Figure 1).
−
R
SERIES
1
R
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
1
S
+
(Ω)
R
ADL5565
G
Differential
R
200
154
118
84.5
52.3
24.9
0
78.7
59
42.2
26.7
12.7
0
23.7
13.7
0
SHUNT
SERIES
, to match to the source
and the ac coupling
(Ω)
ADL5565
Differential
R
57.6
57.6
59
60.4
61.9
64.9
66.5
69.8
73.2
76.8
82.5
88.7
100
113
133
200
SHUNT
(Ω)
5
(5)