AD8330_06 Datasheet, PDF (1/32 Pages) Analog Devices – Low Cost DC to 150 MHz Variable Gain Amplifier

FEATURES
Fully differential signal path and also used
with single-sided signals
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
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
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 ±2 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 ±2 V. This can 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 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.
1 _{Protected by U.S. Patent No. 5,969,657; other patents pending.}
Rev. C
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Low Cost DC to 150 MHz
Variable Gain Amplifier
AD8330
FUNCTIONAL BLOCK DIAGRAM
16
ENBL
15
OFST
14
13
VPOS CNTR
1 VPSI
BIAS AND V_REF
INHI
2
INLO
3
VGA CORE
CM AND ^{VPSO 12}
OFFSET
CONTROL
OPHI
11
OUTPUT
STAGES
OPLO
10
MODE
4
GAIN INTERFACE
OUTPUT ^{CMOP 9}
CONTROL
VDBS
5
CMGN
6
COMM
7
Figure 1.
VMAG
8
Using VMAG, 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,
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.
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/2.
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.
The AD8330 is available in 16-lead LFCSP and 16-lead QSOP
packages and is specified for operation from −40°C to +85°C.
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