VCA821IDGSRG4 Datasheet, PDF (1/38 Pages) Texas Instruments – Ultra-Wideband, > 40dB Gain Adjust Range, Linear in dB VARIABLE GAIN AMPLIFIER

VCA821
VCA821
VCA821
www.ti.com ....................................................................................................................................... SBOS407B – DECEMBER 2007 – REVISED DECEMBER 2008
Ultra-Wideband, > 40dB Gain Adjust Range, Linear in dB
VARIABLE GAIN AMPLIFIER
FEATURES
1
•23 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
APPLICATIONS
• AGC RECEIVERS with RSSI
• DIFFERENTIAL LINE RECEIVERS
• PULSE AMPLITUDE COMPENSATION
• VARIABLE ATTENUATORS
• VOLTAGE-TUNABLE ACTIVE FILTERS
V_IN1
V_IN2
+V_IN
R_F
R_S
R_G+
R₁
R_G
FB
VCA821
C₁
R_G-
-V_IN
20W
R_S
R_L
V_OUT
C_L
Differential Equalizer
9
Equalized Frequency Response
6
3
0
Initial Frequency Response
-3 _{of the VCA821 with RC Load}
-6
-9
-12
-15
-18
-21
-24
1M
10M
100M
1G
Frequency (Hz)
Differential Equalization of an RC Load
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
SINGLES
VCA810
—
—
—
—
VCA820
VCA821
VCA822
VCA824
DUALS
—
VCA2612
VCA2613
VCA2615
VCA2617
—
—
—
—
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
1
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.
2
All other trademarks are the property of their respective owners.
3
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 © 2007–2008, Texas Instruments Incorporated