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PDF OPA686 Data sheet ( Hoja de datos )
| Número de pieza | OPA686 | |
| Descripción | Wideband / Low Noise / Voltage Feedback OPERATIONAL AMPLIFIER | |
| Fabricantes | Burr-Brown | |
| Logotipo |  |
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® OPA686
OPA686
For most current data sheet and other product
information, visit www.burr-brown.com
OPA686
TM Wideband, Low Noise,
Voltage Feedback OPERATIONAL AMPLIFIER
FEATURES
q HIGH BANDWIDTH: 250MHz (G = +10)
q LOW INPUT VOLTAGE NOISE: 1.3nV/√Hz
q VERY LOW DISTORTION: –90dBc (5MHz)
q HIGH SLEW RATE: 600V/µs
q HIGH DC ACCURACY
q LOW SUPPLY CURRENT: 12mA
q HIGH GAIN BANDWIDTH PRODUCT:
1600MHz
q STABLE FOR GAINS ≥ 7
APPLICATIONS
q HIGH DYNAMIC RANGE ADC PREAMP
q LOW NOISE, WIDEBAND,
TRANSIMPEDANCE AMPLIFIER
q WIDEBAND, HIGH GAIN AMPLIFIER
q LOW NOISE DIFFERENTIAL RECEIVER
q VDSL LINE RECEIVER
q ULTRASOUND CHANNEL AMPLIFIER
q IMPROVED REPLACEMENT FOR THE
CLC425
DESCRIPTION
The OPA686 combines very high gain bandwidth and large
signal performance with very low input voltage noise while
dissipating a low 12mA supply current. The classical differen-
tial input stage, along with two stages of forward gain and a
high power output stage, combine to make the OPA686 an
exceptionally low distortion amplifier with excellent DC accu-
racy and output drive. The voltage feedback architecture allows
all standard op amp applications to be implemented with very
high performance.
The combination of low input voltage and current noise, along
with a 1.6GHz gain bandwidth product, make the OPA686 an
ideal amplifier for wideband transimpedance stages. As a volt-
age gain stage, the OPA686 is optimized for a flat response at a
gain of +10 and is guaranteed stable down to a noise gain of +7.
A new external compensation technique can be used to give a
very flat frequency response below the minimum stable gain
for the OPA686, further improving its already exceptional
distortion performance. Using this compensation makes the
OPA686 one of the premier 12- to 14-bit analog-to-digital
converter input drivers. The supply current for the OPA686 is
precisely trimmed to 12.4mA at +25°C. This, along with
carefully defined supply current tempcos in the input and
output stages, combine to provide exceptional performance
over the full specified temperature range.
OPA686 RELATED PRODUCTS
SINGLES
OPA643
OPA687
DUALS
OPA2686
INPUT NOISE
VOLTAGE (nV/√Hz)
2.3
1.3
0.95
GAIN BANDWIDTH
PRODUCT (MHz)
800
1600
3600
100pF
+5V
Supply decoupling
not shown.
0.1µF 50kΩ OPA686
VO
λ IS
–5V 50kΩ
10pF
Photodiode
0.2pF
–VB
High Gain, 20MHz Transimpedance Amplifier
100
95
90
85
80
75
70
65
60
0.1
20log (50kΩ) = 94dBΩ
1 10
Frequency (MHz)
100
International 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/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©1997 Burr-Brown Corporation
PDS-11370D
OPPrinAted6in8U6.S.A. May, 2000
®
1 page  
TYPICAL PERFORMANCE CURVES: VS = ±5V (CONT)
At TA = +25°C, G = +10, RG = 50Ω, and RL = 100Ω, unless otherwise noted. See 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 = 100Ω
RL = 200Ω
1
Output Voltage (Vp-p)
RL = 500Ω
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 = 500Ω
RL = 500Ω
RL = 200Ω
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 OPA686
5 Page 
the primary through to the secondary as a 200Ω source
impedance and likewise, the 200Ω RG resistor is reflected
through to the transformer primary as a 50Ω input match-
ing impedance. The noise gain (NG) to the amplifier
output is then 1+ 1000/400 = 3.5V/V. Taking the op amp’s
1.3nV/√Hz input voltage noise times this noise gain to the
output, then reflecting this noise term to the input side of
the RG resistor, divides it by 5. This gives a net gain of 0.7
for the non-inverting input voltage noise when reflected to
the input point for the op amp circuit. This is further
reduced when referred back to the transformer primary.
The 14dB gain to the matched load for the circuit of Figure
6 is precisely controlled (±0.2dB) and gives a 6dB noise
figure at the input of the transformer. The DC noise gain for
this circuit (3.5) is below the specified minimum stable gain.
This will improve the distortion performance at frequencies
below 20MHz from those shown in the Typical Performance
Curves. Adding the inverting compensation capacitors holds
this configuration stable as described in the previous section.
Measured results show 140MHz small-signal bandwidth for
the circuit of Figure 6 with ±0.1dB flatness through 50MHz.
The OPA686 will easily deliver a 2Vp-p ADC full-scale
input at the matched 50Ω load. Two-tone testing at 20MHz
for the circuit of Figure 6 (1Vp-p for each test tone) shows
that the two-tone intermodulation intercept has improved to
40dBm versus the 35dBm shown in the Typical Perfor-
mance Curves, giving a 72dBc SFDR for the two 4dBm test
tones at the load .
DESIGN-IN TOOLS
DEMONSTRATION BOARDS
Two PC boards are available to assist in the initial evaluation
of circuit performance using the OPA686 in its two package
styles. Both of these are available free as an unpopulated PC
board delivered with descriptive documentation. The sum-
mary information for these boards is shown in the table
below.
PRODUCT
OPA686U
OPA686N
PACKAGE
BOARD
PART
NUMBER
8-Pin SO-8
DEM-OPA68xU
5-Lead SOT23-5 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 OPA686 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 Applications
department (1-800-548-6132). The Applications department
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 har-
monic distortion characteristics. These models do not at-
tempt to distinguish between the package types in their
small-signal AC performance.
OPERATING SUGGESTIONS
SETTING RESISTOR VALUES TO MINIMIZE NOISE
The OPA686 provides a very low input noise voltage while
requiring a low 12mA quiescent current. To take full advan-
tage of this low input noise, careful attention to the other
possible noise contributors is required. Figure 7 shows the
op amp noise analysis model with all the noise terms
included. In this model, all the noise terms are taken to be
noise voltage or current density terms in either nV/√Hz or
pA/√Hz.
ENI
RS IBN
OPA686
EO
ERS
√4kTRS
4kT
RG
RF
√4kTRF
RG IBI
4kT = 1.6E –20J
at 290°K
FIGURE 7. Op Amp Noise Analysis Model.
The total output spot noise voltage can be computed as the
square root of the squared contributing terms to the output
noise voltage. This computation adds all the contributing
noise powers at the output by superposition, then takes the
square root to get back to a spot noise voltage. Equation 1
shows the general form for this output noise voltage using
the terms shown in Figure 7.
Equation 1
( )( ) ( )EO = ENI2 + IBNRS 2 + 4kTRS NG2 + IBIRF 2 + 4kTRFNG
Dividing this expression by the noise gain (NG = 1+RF/RG)
will give the equivalent input-referred spot noise voltage at
the non-inverting input as shown in Equation 2.
Equation 2
( )EN =
ENI2 +
I BN R S
2
+
4 kTR S
+
I BI R F
NG
2
+
4 kTR F
NG
®
11 OPA686
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet OPA686.PDF ] | |
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