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VCA822
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SBOS343A–SEPTEMBER 2007–REVISED OCTOBER 2007
Wideband, > 40dB Gain Adjust Range, Linear in V/V
VARIABLE GAIN AMPLIFIER
1
FEATURES
DESCRIPTION
23
•
150MHz SMALL-SIGNAL BANDWIDTH
(G = +10V/V)
The VCA822 is a dc-coupled, wideband, linear in V/V,
continuously variable, voltage-controlled gain
amplifier. It provides differential input to
single-ended conversion with a high-impedance gain
control input used to vary the gain down 40dB from
the nominal maximum gain set by the gain resistor
(RG) and feedback resistor (RF).
•
•
•
•
•
•
137MHz, 5VPP BANDWIDTH (G = +10V/V)
0.1dB GAIN FLATNESS to 28MHz
1700V/µs SLEW RATE
a
> 40dB GAIN ADJUST RANGE
HIGH GAIN ACCURACY: 20dB ±0.3dB
HIGH OUTPUT CURRENT: ±160mA
The VCA822 internal architecture consists of two
input buffers and an output current feedback amplifier
stage integrated with a multiplier core to provide a
complete variable gain amplifier (VGA) system that
does not require external buffering. The maximum
gain is set externally with two resistors, providing
flexibility in designs. The maximum gain is intended
to be set between +2V/V and +100V/V. Operating
from ±5V supplies, the gain control voltage for the
VCA822 adjusts the gain linearly in V/V as the control
voltage varies from +1V to –1V. For example, set for
a maximum gain of +10V/V, the VCA822 provides
10V/V, at +1V input, to 0.1V/V at –1V input of gain
control range. The VCA822 offers excellent gain
APPLICATIONS
•
•
•
•
•
•
DIFFERENTIAL LINE RECEIVERS
DIFFERENTIAL EQUALIZERS
PULSE AMPLITUDE COMPENSATION
VARIABLE ATTENUATORS
VOLTAGE-TUNABLE ACTIVE FILTERS
DROP-IN UPGRADE TO LMH6503
RF
VIN1
+VIN
RG+
RS
linearity. For
a
20dB maximum gain, and
a
RL
FB
VCA822
R1
C1
RG
VOUT
gain-control input voltage varying between 0V and
1V, the gain does not deviate by more than ±0.3dB
(maximum at +25°C).
CL
RG-
VIN2
-VIN
20W
RS
Table 1. VCA822 RELATED PRODUCTS
GAIN
ADJUST
RANGE
(dB)
INPUT
NOISE
(nV/√Hz)
SIGNAL
BANDWIDTH
(MHz)
Figure 1. Differential Equalizer
SINGLES
VCA810
—
DUALS
—
80
45
45
52
48
40
40
40
40
2.4
1.25
1
35
80
9
6
VCA2612
VCA2613
VCA2615
VCA2617
—
Equalized Frequency
Response
—
80
3
—
0.8
4.1
8.2
7.0
8.2
7.0
50
0
-3
—
50
-6
VCA820
VCA821
VCA822
VCA824
150
420
150
420
Initial Frequency Response
of VCA822 with RC Load
-9
—
-12
-15
-18
-21
-24
—
—
RL = 75W
CF = 100pF
1M
10M
100M
Frequency (Hz)
1G
Figure 2. Differential Equalization of an RC Load
1
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Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2
3
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All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2007, Texas Instruments Incorporated