AD604ARZ Analog Devices Inc, AD604ARZ Datasheet - Page 13

• Manufacturer Part Number: AD604ARZ
• Description: IC AMP VGA DUAL ULN 40MA 24SOIC
• Manufacturer: Analog Devices Inc
• Series: X-AMP®r
• Type: Var Gain Ampr

Specifications of AD604ARZ

• Amplifier Type: Variable Gain
• Number Of Circuits: 2
• Slew Rate: 170 V/µs
• -3db Bandwidth: 40MHz
• Current - Input Bias: 400nA
• Current - Supply: 32mA
• Current - Output / Channel: 40mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (7.5mm Width)
• No. Of Amplifiers: 2
• Bandwidth: 40MHz
• Gain Accuracy: 3dB
• No. Of Channels: 1
• Amplifier Case Style: SOIC
• No. Of Pins: 24
• Operating Temperature Range: -40°C To +85°C
• Svhc: No SVHC (18-Jun-2010)
• Package: RoHS Compliant
• Number Of Channels: 2
• Number Of Elements: 6
• Power Supply Requirement: Dual
• Common Mode Rejection Ratio: 20dB
• Voltage Gain Db: 54dB
• Input Resistance: 0.3@±5VMohm
• Input Bias Current: 27000@±5VnA
• Single Supply Voltage (typ): Not RequiredV
• Dual Supply Voltage (typ): ±5V
• Power Dissipation: 1.7W
• Rail/rail I/o Type: No
• Single Supply Voltage (min): Not RequiredV
• Single Supply Voltage (max): Not RequiredV
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 24
• Package Type: SOIC W
• Supply Voltage Range: ± 5V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AD604-EVALZ - BOARD EVAL FOR AD604 AMP
• Output Type: -
• Voltage - Supply, Single/dual (±): -
• Gain Bandwidth Product: -
• Voltage - Input Offset: -
• Lead Free Status / Rohs Status: Compliant

THEORY OF OPERATION
The AD604 is a dual-channel VGA with an ultralow noise
preamplifier. Figure 37 shows the simplified block diagram of
one channel. Each identical channel consists of a preamplifier
with gain setting resistors (R5, R6, and R7) and a single-supply
X-AMP® (hereafter called DSX, differential single-supply X-AMP)
made up of the following:
•
•
•
•
The preamplifier is powered by a ±5 V supply, while the DSX
uses a single +5 V supply. The linear-in-dB gain response of the
AD604 can generally be described by
Each channel provides between 0 dB to 48.4 dB and 6 dB to 54.4
dB of gain, depending on the user-determined preamplifier
gain. The center 40 dB of gain is exactly linear-in-dB while the
gain error increases at the top and bottom of the range. The gain
of the preamplifier is typically either 14 dB or 20 dB but can be
set to intermediate values by a single external resistor (see the
Preamplifier section for details). The gain of the DSX can vary
from −14 dB to +34.4 dB, as determined by the gain control
voltage (VGN). The VREF input establishes the gain scaling;
the useful gain scaling range is between 20 dB/V and 40 dB/V
for a VREF voltage of 2.5 V and 1.25 V, respectively. For
A precision passive attenuator (differential ladder).
A gain control block.
A VOCM buffer with supply splitting resistors
(R3 and R4).
An active feedback amplifier (AFA) with gain setting
resistors (R1 and R2). To understand the active-feedback
amplifier topology, refer to the
AD830 is a practical implementation of the idea.
G (dB) = Gain Scaling (dB/V) × Gain Control (V) +
(Preamp Gain (dB) − 19 dB)
VOCM
VGNx
VREF
PAIx
EXT.
C3
VPOS
R3
200kΩ
R4
200kΩ
AD830
40Ω
32Ω
Figure 37. Simplified Block Diagram of a Single Channel of the AD604
R7
R5
R6
8Ω
COMx
data sheet. The
FBKx
EXT.
PAOx
C1
C2
+DSXx
–DSXx
Rev. G | Page 13 of 32
(1)
175Ω
175Ω
DIFFERENTIAL
ATTENUATOR
example, if the preamp gain is set to 14 dB and VREF is set to
2.50 V (to establish a gain scaling of 20 dB/V), the gain equation
simplifies to
The desired gain can then be achieved by setting the unipolar
gain control (VGN) to a voltage within its nominal operating
range of 0.25 V to 2.65 V (for 20 dB/V gain scaling). The gain is
monotonic for a complete gain control voltage range of 0.1 V to
2.9 V. Maximum gain can be achieved at a VGN of 2.9 V.
The inputs VREF and VOCM are common to both channels.
They are decoupled to ground, minimizing interchannel
crosstalk. For the highest gain scaling accuracy, VREF should
have an external low impedance voltage source. For low accuracy
20 dB/V applications, the VREF input can be decoupled with a
capacitor to ground. In this mode, the gain scaling is determined
by the midpoint between VPOS and GND; therefore, care
should be taken to control the supply voltage to 5 V. The input
resistance looking into the VREF pin is 10 kΩ ± 20%.
The DSX portion of the AD604 is a single-supply circuit, and
the VOCM pin is used to establish the dc level of the midpoint
of this portion of the circuit. The VOCM pin only needs an
external decoupling capacitor to ground to center the midpoint
between the supply voltages (5 V, GND); however, the VOCM
can be adjusted to other voltage levels if the dc common-mode
level of the output is important to the user (for example, see the
section entitled Medical Ultrasound TGC Driving the AD9050,
a 10-Bit, 40 MSPS ADC). The input resistance looking into the
VOCM pin is 45 kΩ ± 20%.
CONTROL
GAIN
G (dB) = 20 (dB/V) × VGN (V) – 5 dB
20Ω
R2
G1
G2
DISTRIBUTED G
820Ω
R1
Ao
M
OUTx
AD604