AD8330 Datasheet, PDF (1/28 Pages) Analog Devices – Low Cost DC-150 MHz Variable Gain Amplifier

Low Cost DC-150 MHz
Variable Gain Amplifier
AD8330^*
FEATURES
Fully Differential Signal Path
May also be Used with Single-Sided Signals
Inputs from 0.3 mV to 1 V rms, Rail-Rail Outputs
Differential R_IN = 1 k⍀; R_OUT (Each Output) 75 ⍀
Automatic Offset Compensation (Optional)
Linear-in-dB and Linear-in-Magnitude Gain Modes
0 dB to 50 dB, for 0 V < V_DBS < 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 < V_MAG < 5 V
Constant Bandwidth: 150 MHz at All Gains
Low Noise: 5 nV/√Hz typical at Maximum Gain
Low Distortion: ≤–62 dBc Typ
Low Power: 20 mA Typ at V_S of 2.7 V – 6 V
Available in Space Saving 3 ؋ 3 LFCSP Package
APPLICATIONS
Pre-ADC Signal Conditioning
75 ⍀ Cable Driving Adjust
AGC Amplifiers
GENERAL DESCRIPTION
The AD8330 is a wideband variable-gain amplifier for use in
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 ± 2 V, allowing sinewave operation at
1 V rms with generous headroom. The output pins can optionally
drive single-sided loads and each swing 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, which
internally defaults to 0.5 V, to provide a peak output of ± 2 V.
This may be raised to 10 V p-p, limited by the supply voltage.
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 will decrease over the same
range, with opposite slope. A second gain control port is provided
at pin VMAG 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.
Using V_MAG, the basic 0 dB to 50 dB range can be repositioned to any
value from 20 dB higher (that is, 20 dB to 70 dB) to at least 30 dB
lower (that is, –30 dB to +20 dB) to suit the application, 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, not only over the basic 50 dB linear-in-dB
*Protected by U.S.Patent No. 5,969,657; other patents pending.
REV. A
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. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
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FUNCTIONAL BLOCK DIAGRAM
16
ENBL
15
OFST
1 _VPSI
BIAS AND V_REF
14
VPOS
CM AND
OFFSET
CONTROL
13
CNTR
VPSO ¹²
INHI
2
OPHI
11
INLO
3
VGA CORE
OUTPUT
STAGES
OPLO
10
MODE
4
GAIN INTERFACE
VDBS
5
CMGN
6
OUTPUT
CONTROL _CMOP ⁹
COMM VMAG
7
8
90
70
50
30
10
–10
–30
–50
100k
1M
10M
FREQUENCY – Hz
100M 300M
Figure 1. AC Response over the Extended Gain Range
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.
An external capacitor at pin OFST sets the high-pass corner of an
offset reduction loop, whose frequency may 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 V_S to accommodate a wide variety of requirements. By
default, the two outputs are positioned at the mid point of the
supply, V_S/2. Other features, such as two levels of power-down
(fully off and a hibernate mode), further extend the practical
value of this exceptionally versatile VGA.
The AD8330 is available in a 16-lead LFCSP and 16-lead QSOP
packages and is specified for operation from –40°C to +85°C.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
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