Low Cost, DC to 150 MHz
Variable Gain Amplifier
AD8330
FUNCTIONAL BLOCK DIAGRAM
FEATURES
16
15
14
13
ENBL
OFST
VPOS
CNTR
Fully differential signal path, also used
with single-sided signals
1
2
3
4
VPSI
VPSO 12
CM AND
OFFSET
Inputs from 0.3 mV to 1 V rms, rail-to-rail outputs
Differential RIN = 1 kΩ; ROUT (each output) 75 Ω
Automatic offset compensation (optional)
Linear-in-dB and linear-in-magnitude gain modes
0 dB to 50 dB, for 0 V < VDBS < 1.5 V (30 mV/dB)
Inverted gain mode: 50 dB to 0 dB at −30 mV/dB
×0.03 to ×10 nominal gain for 15 mV < VMAG < 5 V
Constant bandwidth: 150 MHz at all gains
Low noise: 5 nV/√Hz typical at maximum gain
Low distortion: ≤−62 dBc typical
BIAS AND V
REF
CONTROL
OPHI
11
INHI
OUTPUT
STAGES
VGA CORE
OPLO
10
INLO
MODE
VDBS
CMOP
VMAG
9
OUTPUT
CONTROL
GAIN INTERFACE
CMGN
Low power: 20 mA typical at VS of 2.7 V to 6 V
Available in a space-saving, 3 mm × 3 mm LFCSP package
COMM
5
6
7
8
Figure 1.
APPLICATIONS
Pre-ADC signal conditioning
75 Ω cable driving adjust
AGC amplifiers
GENERAL DESCRIPTION
The AD83301 is a wideband variable gain amplifier for applications
requiring a fully differential signal path, low noise, well-defined
gain, and moderately low distortion, from dc to 150 MHz. The
input pins can also be driven from a single-ended source. The
peak differential input is ±± V, allowing sine wave operation at
1 V rms with generous headroom. The output pins can drive
single-sided loads essentially rail-to-rail. The differential output
resistance is 150 Ω. The output swing is a linear function of the
voltage applied to the VMAG pin that internally defaults to 0.5 V,
providing a peak output of ±± V. This can be raised to 10 V p-p,
limited by the supply voltage.
Using VMAG, the basic 0 dB to 50 dB range can be reposi-
tioned to any value from ±0 dB higher (that is, ±0 dB to 70 dB)
to at least 30 dB lower (that is, –30 dB to +±0 dB) to suit the
application, thereby providing an unprecedented gain range of
over 100 dB. A unique aspect of the AD8330 is that its bandwidth
and pulse response are essentially constant for all gains, over both
the basic 50 dB linear-in-dB range, but also when using the
linear-in-magnitude function. The exceptional stability of the
HF response over the gain range is of particular value in those
VGA applications where it is essential to maintain accurate gain
law-conformance at high frequencies.
The basic gain function is linear-in-dB, controlled by the voltage
applied to Pin VDBS. The gain ranges from 0 dB to 50 dB for
control voltages between 0 V and 1.5 V—a slope of 30 mV/dB.
The gain linearity is typically within ±0.1 dB. By changing the
logic level on Pin MODE, the gain decreases over the same range,
with an opposite slope. A second gain control port is provided at
the VMAG pin and allows the user to vary the numeric gain from
a factor of 0.03 to 10. All the parameters of the AD8330 have low
sensitivities to temperature and supply voltages.
An external capacitor at Pin OFST sets the high-pass corner of
an offset reduction loop, whose frequency can be as low as 5 Hz.
When this pin is grounded, the signal path becomes dc-coupled.
When used to drive an ADC, an external common-mode control
voltage at Pin CNTR can be driven to within 0.5 V of either ground
or VS to accommodate a wide variety of requirements. By default,
the two outputs are positioned at the midpoint of the supply, VS/±.
Other features, such as two levels of power-down (fully off and a
hibernate mode), further extend the practical value of this excep-
tionally versatile VGA.
1
Protected by U.S. Patent No. 5,969,657; other patents pending.
The AD8330 is available in 16-lead LFCSP and 16-lead QSOP
packages and is specified for operation from −40°C to +85°C.
Rev. D
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registeredtrademarks arethe property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2003–2008 Analog Devices, Inc. All rights reserved.
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