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PDF OPA681 Data sheet ( Hoja de datos )
| Número de pieza | OPA681 | |
| Descripción | Wideband / Current Feedback OPERATIONAL AMPLIFIER With Disable | |
| Fabricantes | Burr-Brown | |
| Logotipo |  |
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OPA681
OPA681
OPA681
OPA681
TM Wideband, Current Feedback
OPERATIONAL AMPLIFIER With Disable
FEATURES
q WIDEBAND +5V OPERATION: 225MHz (G = +2)
q UNITY GAIN STABLE: 280MHz (G = 1)
q HIGH OUTPUT CURRENT: 150mA
q OUTPUT VOLTAGE SWING: ±4.0V
q HIGH SLEW RATE: 2100V/µs
q LOW dG/dφ: .001%/.01°
q LOW SUPPLY CURRENT: 6mA
q LOW DISABLED CURRENT: 320µA
APPLICATIONS
q xDSL LINE DRIVER
q BROADBAND VIDEO BUFFERS
q HIGH SPEED IMAGING CHANNELS
q PORTABLE INSTRUMENTS
q ADC BUFFERS
q ACTIVE FILTERS
q WIDEBAND INVERTING SUMMING
q HIGH SFDR IF AMPLIFIER
DESCRIPTION
The OPA681 sets a new level of performance for broadband
current feedback op amps. Operating on a very low 6mA
supply current, the OPA681 offers a slew rate and output
power normally associated with a much higher supply cur-
rent. A new output stage architecture delivers a high output
current with minimal voltage headroom and crossover
distortion. This gives exceptional single-supply operation.
Using a single +5V supply, the OPA681 can deliver a 1V to
4V output swing with over 100mA drive current and 150MHz
bandwidth. This combination of features makes the OPA681
an ideal RGB line driver or single-supply ADC input driver.
The OPA681’s low 6mA supply current is precisely trimmed
at 25°C. This trim, along with low drift over temperature,
guarantees lower guaranteed maximum supply current than
competing products. System power may be further reduced by
using the optional disable control pin. Leaving this disable pin
open, or holding it high, gives normal operation. If pulled low,
the OPA681 supply current drops to less than 320µA while the
output goes into a high impedance state. This feature may be
used for either power savings or for video MUX applications.
OPA681 RELATED PRODUCTS
Voltage Feedback
Current Feedback
Fixed Gain
SINGLES
OPA680
OPA681
OPA682
DUALS
OPA2680
OPA2681
OPA2682
TRIPLES
OPA3680
OPA3681
OPA3682
+5V
DIS
50Ω
V1
50Ω
V2
50Ω
V3
50Ω
V4
50Ω
V5
OPA681
23.7Ω
100Ω
50Ω
RG-58
VO = – (V1 + V2 + V3 + V4 + V5)
50Ω
100MHz, –1dB Compression
= 15dBm
–5V
200MHz RF Summing Amplifier
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/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©1997 Burr-Brown Corporation
PDS-1427C
Printed in U.S.A. March, 1999
1 page  
TYPICAL PERFORMANCE CURVES: VS = ±5V
G = +2, RF = 402Ω, and RL = 100Ω, unless otherwise noted (see Figure 1).
2
1
0
–1
–2
–3
–4
–5
–6
–7
–8
0
SMALL-SIGNAL FREQUENCY RESPONSE
G = +1, RF = 453Ω
G = +2, RF = 402Ω
G = +5, RF = 261Ω
G = +10, RF = 180Ω
125MHz
Frequency (25MHz/div)
250MHz
LARGE-SIGNAL FREQUENCY RESPONSE
8
7 G = +2, RL = 100Ω
6
5 2Vp-p
4
3
2 1Vp-p
4Vp-p
1
0 7Vp-p
–1
–2
0
125MHz
Frequency (25MHz/div)
250MHz
400
300
200
100
0
–100
–200
–300
–400
SMALL-SIGNAL PULSE RESPONSE
G = +2
VO = 0.5Vp-p
Time (5ns/div)
LARGE-SIGNAL PULSE RESPONSE
+4
+3 G = +2
VO = 5Vp-p
+2
+1
0
–1
–2
–3
–4
Time (5ns/div)
LARGE-SIGNAL DISABLE/ENABLE RESPONSE
VDIS
2.0
1.6
1.2
0.8
0.4
G = +2
VIN = +1V
0
Output Voltage
Time (50ns/div)
6.0
4.0
2.0
0
DISABLED FEEDTHROUGH vs FREQUENCY
–45
–50 VDIS = 0
–55
–60
–65
–70
Forward
Reverse
–75
–80
–85
–90
–95
1
10
Frequency (MHz)
100
®
5 OPA681
5 Page 
APPLICATIONS INFORMATION
WIDEBAND CURRENT FEEDBACK OPERATION
The OPA681 gives the exceptional AC performance of a
wideband current feedback op amp with a highly linear, high
power output stage. Requiring only 6mA quiescent current,
the OPA681 will swing to within 1V of either supply rail and
deliver in excess of 135mA guaranteed at room temperature.
This low output headroom requirement, along with supply
voltage independent biasing, gives remarkable single (+5V)
supply operation. The OPA681 will deliver greater than
200MHz bandwidth driving a 2Vp-p output into 100Ω on a
single +5V supply. Previous boosted output stage amplifiers
have typically suffered from very poor crossover distortion
as the output current goes through zero. The OPA681
achieves a comparable power gain with much better linear-
ity. The primary advantage of a current feedback op amp
over a voltage feedback op amp is that AC performance
(bandwidth and distortion) is relatively independent of sig-
nal gain. For similar AC performance at low gain, with
improved DC accuracy, consider the high slew rate, unity
gain stable, voltage feedback OPA680.
Figure 1 shows the DC coupled, gain of +2, dual power
supply circuit configuration used as the basis of the ±5V
Specifications and Typical Performance Curves. For test
purposes, the input impedance is set to 50Ω with a resistor
to ground and the output impedance is set to 50Ω with a
series output resistor. Voltage swings reported in the speci-
fications are taken directly at the input and output pins while
load powers (dBm) are defined at a matched 50Ω load. For
the circuit of Figure 1, the total effective load will be 100Ω
|| 804Ω = 89Ω. The disable control line (DIS) is typically left
open to guarantee normal amplifier operation. One optional
component is included in Figure 1. In addition to the usual
power supply de-coupling capacitors to ground, a 0.1µF
capacitor is included between the two power supply pins. In
practical PC board layouts, this optional added capacitor
will typically improve the 2nd harmonic distortion perfor-
mance by 3dB to 6dB.
Figure 2 shows the AC-coupled, gain of +2, single supply
circuit configuration used as the basis of the +5V Specifica-
tions and Typical Performance Curves. Though not a “rail-
to-rail” design, the OPA681 requires minimal input and
output voltage headroom compared to other very wideband
current feedback op amps. It will deliver a 3Vp-p output
swing on a single +5V supply with greater than 150MHz
bandwidth. The key requirement of broadband single supply
operation is to maintain input and output signal swings
within the usable voltage ranges at both the input and the
output. The circuit of Figure 2 establishes an input midpoint
bias using a simple resistive divider from the +5V supply
(two 806Ω resistors). The input signal is then AC coupled
into this midpoint voltage bias. The input voltage can swing
to within 1.5V of either supply pin, giving a 2Vp-p input
signal range centered between the supply pins. The input
impedance matching resistor (57.6Ω) used for testing is
adjusted to give a 50Ω input match when the parallel
combination of the biasing divider network is included. The
gain resistor (RG) is AC-coupled, giving the circuit a DC
gain of +1—which puts the input DC bias voltage (2.5V) on
the output as well. The feedback resistor value has been
adjusted from the bipolar supply condition to re-optimize for
a flat frequency response in +5V, gain of +2, operation (see
Setting Resistor Values to Optimize Bandwidth). Again, on
a single +5V supply, the output voltage can swing to within
1V of either supply pin while delivering more than 80mA
output current. A demanding 100Ω load to a midpoint bias
is used in this characterization circuit. The new output stage
used in the OPA681 can deliver large bipolar output currents
into this midpoint load with minimal crossover distortion, as
shown by the +5V supply, 3rd harmonic distortion plots.
+5V
+VS
0.1µF
6.8µF
+
50Ω Source
VI 50Ω
OPA681
DIS
50Ω Load
VO 50Ω
+5V
+VS
806Ω
+
0.1µF
6.8µF
0.1µF
DIS
VI
57.6Ω 806Ω OPA681
VO 100Ω
VS/2
0.1µF
RF
402Ω
RF
499Ω
RG
402Ω
–VS
–5V
+ 6.8µF
0.1µF
RG
499Ω
0.1µF
FIGURE 1. DC-Coupled, G = +2, Bipolar Supply, Specifi-
cation and Test Circuit.
FIGURE 2. AC-Coupled, G = +2, Single Supply Specifica-
tion and Test Circuit.
®
11 OPA681
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet OPA681.PDF ] | |
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