VC
A
821
VC
A82
1
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.......................................................................................................................................
SBOS407B – DECEMBER 2007 – REVISED DECEMBER 2008
Ultra-Wideband, > 40dB Gain Adjust Range, Linear in dB
VARIABLE GAIN AMPLIFIER
1
FEATURES
•
710MHz SMALL-SIGNAL BANDWIDTH
(G = +2V/V)
•
320MHz, 4V
PP
BANDWIDTH (G = +10V/V)
•
0.1dB GAIN FLATNESS to 135MHz
•
2500V/µs SLEW RATE
•
> 40dB GAIN ADJUST RANGE
•
HIGH GAIN ACCURACY: 20dB ±0.3dB
•
HIGH OUTPUT CURRENT: ±90mA
23
DESCRIPTION
The VCA821 is a dc-coupled, wideband, linear in dB,
continuously
variable,
voltage-controlled
gain
amplifier. It provides a 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
(R
G
) and feedback resistor (R
F
).
The VCA821 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 6dB and 32dB. Operating from ±5V
supplies, the gain control voltage for the VCA821
adjusts the gain linearly in dB as the control voltage
varies from 0V to +2V. For example, set at a
maximum gain of 20dB, the VCA821 provides 20dB,
at V
G
= +2V, to less than –20dB at V
G
= 0V. The
VCA821 offers excellent gain linearity. For a 20dB
maximum gain, and a gain-control input voltage
varying between +1V and +2V, the gain does not
deviate by more than ±0.3dB (maximum at +25°C).
VCA821 RELATED PRODUCTS
APPLICATIONS
•
•
•
•
•
AGC RECEIVERS with RSSI
DIFFERENTIAL LINE RECEIVERS
PULSE AMPLITUDE COMPENSATION
VARIABLE ATTENUATORS
VOLTAGE-TUNABLE ACTIVE FILTERS
V
IN1
R
S
R
1
C
1
R
G-
V
IN2
R
S
-V
IN
20W
R
G
+V
IN
R
G+
FB
VCA821
C
L
R
L
V
OUT
R
F
Differential Equalizer
9
Equalized Frequency Response
6
3
0
Initial Frequency Response
of the VCA821 with RC Load
SINGLES
—
—
—
—
DUALS
—
—
—
—
—
GAIN
ADJUST
RANGE
(dB)
80
45
45
52
48
40
40
40
40
INPUT
NOISE
(nV/√Hz)
2.4
1.25
1
0.8
4.1
8.2
6.0
8.2
6.0
SIGNAL
BANDWIDTH
(MHz)
35
80
80
50
50
150
420
150
420
Gain (dB)
-3
-6
-9
-12
-15
-18
-21
-24
1M
10M
100M
1G
Frequency (Hz)
Differential Equalization of an RC Load
1
2
3
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
X2Y is a trademark of X2Y Attenuators LLC.
All other trademarks are the property of their respective owners.
Copyright © 2007–2008, Texas Instruments Incorporated
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.
TI [ TEXAS INSTRUMENTS ]
