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PDF OPA2681 Data sheet ( Hoja de datos )
| Número de pieza | OPA2681 | |
| Descripción | Dual Wideband / Current Feedback OPERATIONAL AMPLIFIER With Disable | |
| Fabricantes | Burr-Brown | |
| Logotipo |  |
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®
OPA2681
OPA2681
OPA2681
TM Dual 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 SUPPLY CURRENT: 6mA/ch
q LOW DISABLED CURRENT: 200µA/ch
q ENABLE/DISABLE TIME: 25ns/100ns
APPLICATIONS
q xDSL LINE DRIVER
q MATCHED I/Q CHANNEL AMPLIFIER
q BROADBAND VIDEO BUFFERS
q HIGH SPEED IMAGING CHANNELS
q PORTABLE INSTRUMENTS
q DIFFERENTIAL ADC DRIVERS
q ACTIVE FILTERS
q WIDEBAND INVERTING SUMMING
DESCRIPTION
The OPA2681 sets a new level of performance for broadband dual
current feedback op amps. Operating on a very low 6mA/ch
supply current, the OPA2681 offers a slew rate and output power
normally associated with a much higher supply current. 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 OPA2681 can deliver a 1V to 4V output swing with over
100mA drive current and 150MHz bandwidth. This combination
of features makes the OPA2681 an ideal RGB line driver or single
supply ADC input driver.
+12V
1/2
OPA2681
The OPA2681’s low 6mA/ch supply current is precisely trimmed
at 25°C. This trim, along with low drift over temperature, guaran-
tees lower guaranteed maximum supply current than competing
products. System power may be further reduced by using the
optional disable control pin (SO-14 only). Leaving this disable
pin open, or holding it high, gives normal operation. If pulled low,
the OPA2681 supply current drops to less than 400µA while the
output goes into a high impedance state. This feature may be used
for either power savings or for video MUX applications.
OPA2681 RELATED PRODUCTS
Voltage Feedback
Current Feedback
Fixed Gain
SINGLES
OPA680
OPA681
OPA682
DUALS
OPA2680
OPA2681
OPA2682
TRIPLES
OPA3680
OPA3681
OPA3682
324Ω
12.4Ω 1:2
+6.5V
2kΩ
1µF
2Vp-p
100Ω
2kΩ 324Ω
12.4Ω
100Ω 15Vp-p
1/2
OPA2681
Single Supply ADSL Upstream Driver
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-1440B
Printed in U.S.A. October, 1998
1 page  
TYPICAL PERFORMANCE CURVES: VS = ±5V
G = +2, RF = 402Ω, 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
5.0 6.0
4.0 VDIS
2.0
4.0
2.0
00
2.0 Output Voltage
1.6
1.2
0.8
0.4 G = +2
VIN = +1V
0
(SO-14 only)
Time (50ns/div)
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
1
CHANNEL-TO-CHANNEL CROSSTALK
10
Frequency (MHz)
100
®
5 OPA2681
5 Page 
APPLICATIONS INFORMATION
WIDEBAND CURRENT FEEDBACK OPERATION
The OPA2681 gives the exceptional AC performance of a
wideband current feedback op amp with a highly linear, high
power output stage. Requiring only 6mA/ch. quiescent cur-
rent, the OPA2681 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 OPA2681 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
OPA2681 achieves a comparable power gain with much
better linearity. The primary advantage of a current feedback
op amp over a voltage feedback op amp is that AC perfor-
mance (bandwidth and distortion) is relatively independent
of signal gain. For similar AC performance with improved
DC accuracy, consider the high slew rate, unity gain stable,
voltage feedback OPA2680.
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 (SO-14 only) 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
performance 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 OPA2681 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 75mA
output current. A demanding 100Ω load to a midpoint bias
is used in this characterization circuit. The new output stage
used in the OPA2681 can deliver large bipolar output cur-
rents into this midpoint load with minimal crossover distor-
tion, as shown by the +5V supply, 3rd harmonic distortion
plots.
+5V
0.1µF
+VS
6.8µF
+
50Ω Source
VI 50Ω
1/2
OPA2681
DIS
50Ω Load
VO 50Ω
+5V
+VS
806Ω
+
0.1µF
6.8µF
0.1µF
DIS
VI 57.6Ω 806Ω 1/2
VO 100Ω
OPA2681
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 OPA2681
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet OPA2681.PDF ] | |
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