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Número de pieza | OPA691 | |
Descripción | Quad / Low-Power / Current-Feedback OPERATIONAL AMPLIFIER | |
Fabricantes | Burr-Brown | |
Logotipo | ||
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OPA691
OPA691
OPA691
SBOS226A – DECEMBER 2001– REVISED SEPTEMBER 2002
Wideband, Current Feedback
OPERATIONAL AMPLIFIER With Disable
FEATURES
q FLEXIBLE SUPPLY RANGE:
+5V to +12V Single-Supply
±2.5V to ±6V Dual-Supply
q UNITY-GAIN STABLE: 280MHz (G = 1)
q HIGH OUTPUT CURRENT: 190mA
q OUTPUT VOLTAGE SWING: ±4.0V
q HIGH SLEW RATE: 2100V/µs
q LOW dG/dφ: 0.07% /0.02°
q LOW SUPPLY CURRENT: 5.1mA
q LOW DISABLED CURRENT: 150µA
q WIDEBAND +5V OPERATION: 190MHz (G = +2)
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 OPA691 sets a new level of performance for broadband
current feedback op amps. Operating on a very low 5.1mA
supply current, the OPA691 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 distor-
tion. This gives exceptional single-supply operation. Using a
single +5V supply, the OPA691 can deliver a 1V to 4V output
swing with over 150mA drive current and 190MHz band-
width. This combination of features makes the OPA691 an
ideal RGB line driver or single-supply Analog-to-Digital Con-
verter (ADC) input driver.
The OPA691’s low 5.1mA supply current is precisely trimmed
at 25°C. This trim, along with low drift over-temperature,
ensures lower 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
OPA691 supply current drops to less than 150µA while the
output goes into a high impedance state. This feature may be
used for power savings.
OPA691 RELATED PRODUCTS
Voltage Feedback
Current Feedback
Fixed Gain
SINGLES
OPA690
OPA681
OPA692
DUALS
OPA2690
OPA2691
TRIPLES
OPA3690
OPA3691
OPA3692
+5V
DIS
50Ω
V1
50Ω
V2
50Ω
V3
50Ω
V4
50Ω
V5
OPA691
30Ω
100Ω
–5V
50Ω
RG-58
VO = –(V1 + V2 + V3 + V4 + V5)
50Ω
100MHz, –1dB Compression = 15dBm
200MHz RF Summing Amplifier
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
www.ti.com
Copyright © 2001, Texas Instruments Incorporated
1 page TYPICAL CHARACTERISTICS: VS = ±5V
G = +2, RF = 402Ω, and RL = 100Ω, unless otherwise noted (see Figure 1).
SMALL-SIGNAL FREQUENCY RESPONSE
1
G = +1, RF = 453Ω
0 G = +2,
–1 RF = 402Ω
–2
–3
–4
G = +5, RF = 261Ω
–5
–6 G = +10, RF = 180Ω
–7
–8
0
VO = 0.5Vp-p
125MHz
Frequency (25MHz/div)
250MHz
LARGE-SIGNAL FREQUENCY RESPONSE
7.0
G = +2, RL = 100Ω
6.5 2Vp-p 1Vp-p
6.0
5.5
5.0
4.5
4.0
3.5
4Vp-p
3.0
7Vp-p
2.5
2.0
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)
0.2
0.18
0.16
0.14
0.12
0.1
COMPOSITE VIDEO dG/dP
Video
In
+5
OPA691
402Ω
Video
Loads
402Ω
Optional 1.3kΩ
–5 Pull-Down
No Pull-Down
With 1.3kΩ Pull-Down
dG
dG
0.08
0.06
0.04
0.02
dP
dP
0
12 3
Number of 150Ω Loads
4
DISABLED FEEDTHROUGH vs FREQUENCY
–45
–50 VDIS = 0
–55
–60
–65
–70
–75
–80 Reverse
–85
–90
Forward
–95
–100
0.3
1
10
Frequency (MHz)
100
OPA691
SBOS226A
www.ti.com
5
5 Page APPLICATIONS INFORMATION
WIDEBAND CURRENT FEEDBACK OPERATION
The OPA691 gives the exceptional AC performance of a
wideband current feedback op amp with a highly linear, high
power output stage. Requiring only 5.1mA quiescent current,
the OPA691 will swing to within 1V of either supply rail and
deliver in excess of 160mA at room temperature. This low
output headroom requirement, along with supply voltage
independent biasing, gives remarkable single (+5V) supply
operation. The OPA691 will deliver greater than 200MHz
bandwidth driving a 2Vp-p output into 100Ω on a single +5V
supply. Previous boosted output stage amplifiers have typi-
cally suffered from very poor crossover distortion as the
output current goes through zero. The OPA691 achieves a
comparable power gain with much better linearity. The pri-
mary advantage of a current feedback op amp over a voltage
feedback op amp is that AC performance (bandwidth and
distortion) is relatively independent of signal gain. For similar
AC performance at low gains, with improved DC accuracy,
consider the high slew rate, unity-gain stable, voltage feed-
back OPA690.
Figure 1 shows the DC-coupled, gain of +2, dual power-
supply circuit configuration used as the basis of the ±5V
Electrical Characteristic tables and Typical Characteristic
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 specifications 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 ensure 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 Electrical
Characteristic tables and Typical Characteristic curves.
Though not a “rail-to-rail” design, the OPA691 requires mini-
mal 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 combi-
nation 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 ad-
justed 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 120mA output
current. A demanding 100Ω load to a mid-point bias is used
in this characterization circuit. The new output stage used in
the OPA691 can deliver large bipolar output currents into this
mid-point 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
OPA691
DIS
50Ω Load
VO 50Ω
0.1µF
RF
402Ω
RG
402Ω
–VS
–5V
+ 6.8µF
0.1µF
FIGURE 1. DC-Coupled, G = +2, Bipolar Supply, Specifica-
tion and Test Circuit.
+5V
+VS
806Ω
+
0.1µF
6.8µF
0.1µF
DIS
VI
57.6Ω 806Ω OPA691
VO 100Ω
VS/2
RF
453Ω
RG
453Ω
0.1µF
FIGURE 2. AC-Coupled, G = +2, Single-Supply Specification
and Test Circuit.
OPA691
SBOS226A
www.ti.com
11
11 Page |
Páginas | Total 24 Páginas | |
PDF Descargar | [ Datasheet OPA691.PDF ] |
Número de pieza | Descripción | Fabricantes |
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