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PDF OPA687 Data sheet ( Hoja de datos )
| Número de pieza | OPA687 | |
| Descripción | Wideband / Ultra-Low Noise / Voltage Feedback OPERATIONAL AMPLIFIER With Power Down | |
| Fabricantes | Burr-Brown | |
| Logotipo |  |
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®
OPA687
OPA687
For most current data sheet and other product
information, visit www.burr-brown.com
TM Wideband, Ultra-Low Noise,
Voltage Feedback OPERATIONAL AMPLIFIER
With Power Down
FEATURES
q HIGH GAIN BANDWIDTH: 3.8GHz
q LOW INPUT VOLTAGE NOISE: 0.95nV/√Hz
q VERY LOW DISTORTION: –95dBc (5MHz)
q LOW DISABLED POWER: 2mW
q VERY HIGH SLEW RATE: 900V/µs
q STABLE FOR G ≥ 12
APPLICATIONS
q LOW DISTORTION ADC DRIVER
q OC-3 FIBER OPTIC RECEIVER
q LOW NOISE DIFFERENTIAL AMPLIFIERS
q EQUALIZING RECEIVERS
q ULTRASOUND CHANNEL AMPLIFIERS
q IMPROVED REPLACEMENT FOR THE
CLC425
DESCRIPTION
The OPA687 combines a very high gain bandwidth and
large signal performance with an ultra-low input noise
voltage (0.95nV/√Hz) while dissipating only 18mA sup-
ply current. Where power savings is paramount, the
OPA687 also includes an optional power down pin that,
when pulled low, will disable the amplifier and decrease
the quiescent current to only 1% of its powered up value.
This optional feature may be left disconnected to insure
normal amplifier operation when no power-down is re-
quired.
The combination of low input voltage and current noise,
along with a 3.8GHz gain bandwidth product, make the
OPA687 an ideal amplifier for wideband transimpedance
stages. As a voltage gain stage, the OPA687 is opti-
mized for a flat frequency response at a gain of +20 and
is guaranteed stable down to gains of +12. New external
compensation techniques allows the OPA687 to be used
at any inverting gain with excellent frequency response
control. Using this compensation can give an extremely
high dynamic range ADC driver to support > 40MSPS
12- and 14-bit converters.
OPA687 RELATED PRODUCTS
SINGLES
DUAL
INPUT NOISE GAIN BANDWIDTH
VOLTAGE (nV/√Hz) PRODUCT (MHz)
OPA642
OPA643
OPA686
OPA2686
2.7
2.3
1.3
210
800
1600
50Ω Source
< 6dB
Noise
Figure
VCM
100Ω
1:2 39pF
39pF
+5V
OPA687
1.7pF
–5V
850Ω
850Ω
20Ω
100Ω
VCM
+5V
1.7pF
OPA687
20Ω
–5V
Ultra-High Dynamic Range
Differential Input ADC Driver
+5V
VIN+
80pF
ADS852
14-Bit
65MSPS
VIN–
80pF
–60
–65
4Vp-p
–70
–75 2Vp-p
–80
–85
0
5 10 15 20 25 30 35 40 45 50
Center Frequency (MHz)
Measured 2-Tone, 3rd-Order Distortion for
Differential ADC Driver.
IInternational Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111
Twx: 910-952-1111 • Internet: http://www.burr-brown.com/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product In
©1998 Burr-Brown Corporation
PDS-1372C
OPPrinAted6in8U7.S.A. May, 2000
®
1 page  
TYPICAL PERFORMANCE CURVES: VS = ±5V (CONT)
RF = 750Ω, RG = 39.2Ω, G = +20 and RL = 100Ω, unless otherwise noted (Figure 1).
–70
–80
–90
–100
–110
0.1
5MHz 2nd HARMONIC DISTORTION
vs OUTPUT VOLTAGE
RL = 100Ω
RL = 200Ω
RL = 500Ω
1
Output Voltage (Vp-p)
10
–70
–80
–90
–100
–110
0.1
5MHz 3rd HARMONIC DISTORTION
vs OUTPUT VOLTAGE
RL = 500Ω
RL = 100Ω
RL =200Ω
1
Output Voltage (Vp-p)
10
–60
–70
–80
–90
–100
0.1
10MHz 2nd HARMONIC DISTORTION
vs OUTPUT VOLTAGE
RL = 100Ω
RL = 200Ω
RL = 500Ω
1
Output Voltage (Vp-p)
10
–60
–70
–80
–90
–100
0.1
10MHz 3rd HARMONIC DISTORTION
vs OUTPUT VOLTAGE
RL = 200Ω
RL = 100Ω
RL = 500Ω
1
Output Voltage (Vp-p)
10
–50
–60
–70
–80
–90
0.1
20MHz 2nd HARMONIC DISTORTION
vs OUTPUT VOLTAGE
RL = 100Ω
RL = 200Ω
RL = 500Ω
1
Output Voltage (Vp-p)
10
–50
–60
–70
–80
–90
0.1
20MHz 3rd HARMONIC DISTORTION
vs OUTPUT VOLTAGE
RL = 100Ω
RL = 200Ω
RL = 500Ω
1
Output Voltage (Vp-p)
10
®
5 OPA687
5 Page 
LOW NOISE FIGURE, HIGH DYNAMIC
RANGE AMPLIFIER
The low input noise voltage of the OPA687 and its very high
2-tone intercept can be used to good advantage as a fixed-
gain IF amplifier. While input noise figures in the 10dB
range (for a matched 50Ω input) are easily achieved with
just the OPA687, Figure 5 shows a technique to reduce the
noise figure even further while providing a broadband, high
gain IF amplifier stage using two stages of the OPA687.
This circuit uses two stages of forward gain with an overall
feedback loop to set the input impedance match. The input
transformer provides both a noiseless voltage gain and a
signal inversion to retain an overall non-inverting signal
path from PI to PO—since the 2nd amplifier stage is invert-
ing to provide the correct feedback polarity through the
6.19kΩ resistor. To achieve a 50Ω input match at the
primary of the 1:2 transformer, the secondary must see a
200Ω load impedance. At higher frequencies, the match is
provided by the 200Ω resistor in series with 10pF. At lower
signal frequencies (f < 80MHz), the input match is set by the
feedback through the 6.19kΩ resistor. The low noise figure
(5dB) for this circuit is achieved by using the transformer,
the low voltage noise OPA687, and the input match set by
feedback. The first stage amplifier provides a gain of +15.
The very high SFDR is provided by operating the output
stage a low signal gain of –2 and using the inverting
compensation to hold it stable. Depending on the load that
is driven, this circuit can give a 2-tone SFDR that exceeds
90dB through 30MHz. Besides offering a very high dynamic
range, this circuit improves on standard IF amplifiers by
offering a precisely controlled gain and a very flexible
output load driving capability.
DESIGN-IN TOOLS
DEMONSTRATION BOARDS
Two PC boards are available to assist in the initial evalua-
tion of circuit performance using the OPA687 in its two
package styles. Both of these are available free as an
unpopulated PC board delivered with descriptive documen-
tation. The summary information for these boards is shown
in the table below.
PRODUCT
OPA687U
OPA687N
PACKAGE
BOARD
PART
NUMBER
8-Pin SO-8
DEM-OPA68xU
6-Lead SOT23-6 DEM-OPA6xxN
LITERATURE
REQUEST
NUMBER
MKT-351
MKT-348
Contact the Burr-Brown applications support line to request
any of these boards.
MACROMODELS AND APPLICATIONS SUPPORT
Computer simulation of circuit performance using SPICE is
often useful when analyzing the performance of analog
circuits and systems. This is particularly true for video and
RF amplifier circuits where parasitic capacitance and induc-
tance can have a major effect on circuit performance. A
SPICE model for the OPA687 is available through either the
Burr-Brown Internet web page (http://www.burr-brown.com)
or as one model on a disk from the Burr-Brown Applica-
tions department (1-800-548-6132). The Applications de-
partment is also available for design assistance at this
number. These models do a good job of predicting small-
signal AC and transient performance under a wide variety of
operating conditions. They do not do as well in predicting
the harmonic distortion characteristics. These models do not
attempt to distinguish between the package types in their
small-signal AC performance.
50Ω Source
PI 1:2
5dB
Noise
Figure
6.19kΩ
Input match
set by this
feedback path
OPA687
PO
200Ω
10pF
OPA687
420Ω
30.1Ω
750Ω
1.5kΩ
46pF
1.6pF
Overall Gain PO = 35.6dB
PI
FIGURE 5. Very High Dynamic Range High Gain Amplifier.
11 OPA687
®
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet OPA687.PDF ] | |
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