AD600JR Analog Devices Inc, AD600JR Datasheet - Page 16

• Manufacturer Part Number: AD600JR
• Description: IC AMP VGA DUAL LN 50MA 16SOIC
• Manufacturer: Analog Devices Inc
• Series: X-AMP®r

Specifications of AD600JR

• Rohs Status: RoHS non-compliant
• Amplifier Type: Variable Gain
• Number Of Circuits: 2
• Slew Rate: 275 V/µs
• -3db Bandwidth: 35MHz
• Current - Input Bias: 350nA
• Current - Supply: 11mA
• Current - Output / Channel: 50mA
• Voltage - Supply, Single/dual (±): ±4.75 V ~ 5.25 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.300", 7.5mm Width)
• Output Type: -
• Gain Bandwidth Product: -
• Voltage - Input Offset: -

AD600/AD602
REALIZING OTHER GAIN RANGES
Larger gain ranges can be accommodated by cascading
amplifiers. Combinations built by cascading two amplifiers
include −20 dB to +60 dB (using one AD602), −10 dB to +70 dB
(using ½ of an AD602 followed by ½ of an AD600), and 0 dB to
80 dB (using one AD600). In multiple-channel applications,
extra protection against oscillation can be provided by using
amplifier sections from different packages.
AN ULTRALOW NOISE VCA
The two channels of the AD600 or AD602 can operate in
parallel to achieve a 3 dB improvement in noise level, providing
1 nV/√Hz without any loss of gain accuracy or bandwidth.
In the simplest case, as shown in Figure 35, the signal inputs
A1HI and A2HI are tied directly together. The outputs A1OP
and A2OP are summed via R1 and R2 (100 Ω each), and the
control inputs C1HI/C2HI and C1LO/C2LO operate in parallel.
Using these connections, both the input and output resistances
are 50 Ω. Thus, when driven from a 50 Ω source and terminated
in a 50 Ω load, the gain is reduced by 12 dB, so the gain range
becomes –12 dB to +28 dB for the AD600 and −22 dB to
+18 dB for the AD602. The peak input capability remains
unaffected (1 V rms at the IC pins, or 2 V rms from an
unloaded 50 Ω source). The loading on each output, with a
50 Ω load, is effectively 200 Ω, because the load current is
shared between the two channels, so the overall amplifier still
meets its specified maximum output and distortion levels for a
200 Ω load. This amplifier can deliver a maximum sine wave
power of 10 dBm to the load.
V
IN
Figure 35. An Ultralow Noise VCA Using the AD600 or AD602
C1LO
A1LO
A2LO
C2LO
GAT1
GAT2
A1HI
A2HI
1
2
3
4
5
6
7
8
+
–
–
+
GAIN-CONTROL
AD600 OR
VOLTAGE
AD602
– +
V
G
A1
A2
REF
16
15
14
13
12
11
10
9
VNEG
A2CM
C1HI
A1CM
A1OP
VPOS
A2OP
C2HI
+5V
–5V
100Ω
100Ω
V
Rev. E | Page 16 of 28
50Ω
OUT
A LOW NOISE, 6 dB PREAMPLIFIER
In some ultrasound applications, a high input impedance
preamplifier is needed to avoid the signal attenuation that
results from loading the transducer by the 100 Ω input resistance
of the X-AMP. High gain cannot be tolerated because the
peak transducer signal is typically ±0.5 V, while the peak input
capability of the AD600 or AD602 is only slightly more than
±1 V. A gain of 2 is a suitable choice. It can be shown that if the
preamplifier’s overall referred-to-input (RTI) noise is the same
as that due to the X-AMP alone (1.4 nV/√Hz), the input noise
of nX2 preamplifier must be √(3/4) times as large, that is,
1.2 nV/√Hz.
An inexpensive circuit using complementary transistor types
chosen for their low r
determined by the ratio of the net collector load resistance to
the net emitter resistance. It is an open-loop amplifier. The gain
is ×2 (6 dB) only into a 100 Ω load, assumed to be provided by
the input resistance of the X-AMP; R2 and R7 are in shunt
with this load, and their value is important in defining the gain.
For small-signal inputs, both transistors contribute an equal
transconductance that is rendered less sensitive to signal level
by the emitter resistors, R4 and R5. They also play a dominant
role in setting the gain.
V
IN
Figure 36. A Low Noise Preamplifier for the AD600/AD602
42.2Ω
42.2Ω
1µF
1µF
R4
R5
49.9Ω
49.9Ω
174Ω
174Ω
R1
R2
R7
R8
–5V
+5V
–5V
+5V
bb
R3
562Ω
R6
562Ω
is shown in Figure 36. The gain is
Q1
MRF904
Q2
MM4049
INPUT
GROUND
1µF
1µF
0.1µF
0.1µF
GROUND
OUTPUT
100Ω
R
IN
OF X-AMP