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PDF OPA843 Data sheet ( Hoja de datos )
| Número de pieza | OPA843 | |
| Descripción | Wideband / Low Distortion / Medium Gain / Voltage-Feedback OPERATIONAL AMPLIFIER | |
| Fabricantes | Burr-Brown | |
| Logotipo |  |
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OPA843
OPA843
SBOS268A – DECEMBER 2002 – OCTOBER 2003
Wideband, Low Distortion, Medium Gain,
Voltage-Feedback OPERATIONAL AMPLIFIER
FEATURES
q HIGH BANDWIDTH: 260MHz (G = +5)
q GAIN BANDWIDTH PRODUCT: 800MHz
q LOW INPUT VOLTAGE NOISE: 2.0nV/√Hz
q VERY LOW DISTORTION: –96dBc (5MHz)
q HIGH OPEN-LOOP GAIN: 110dB
q FAST 12-BIT SETTLING: 10.5ns (0.01%)
q LOW INPUT OFFSET VOLTAGE: 300µV
q OUTPUT CURRENT: ±100mA
APPLICATIONS
q ADC/DAC BUFFER AMPLIFIER
q LOW DISTORTION “IF” AMPLIFIER
q ACTIVE FILTERS
q LOW-NOISE RECEIVER
q WIDEBAND TRANSIMPEDANCE
q TEST INSTRUMENTATION
q PROFESSIONAL AUDIO
q OPA643 UPGRADE
+5V
DESCRIPTION
The OPA843 provides a level of speed and dynamic range
previously unattainable in a monolithic op amp. Using a high
Gain Bandwidth (GBW), two gain-stage design, the OPA843
gives a medium gain range device with exceptional dynamic
range. The “classic” differential input complements this high
dynamic range with DC precision beyond most high-speed
amplifier products. Very low input offset voltage and current,
high Common-Mode Rejection Ratio (CMRR) and Power-
Supply Rejection Ratio (PSRR), and high open-loop gain
combine to give a high DC precision amplifier along with low
noise and high 3rd-order intercept.
12- to 16-bit converter interfaces will benefit from this combi-
nation of features. High-speed transimpedance applications
can be implemented with exceptional DC precision as well.
Differential configurations using two OPA843s can deliver
very low distortion to high output voltages, as shown below.
OPA843 RELATED PRODUCTS
SINGLES
INPUT NOISE
VOLTAGE (nV/√Hz )
OPA842
OPA846
OPA847
2.6
1.2
0.85
GAIN-BANDWIDTH
PRODUCT (MHz)
200
1750
3900
OPA843
1:1
VI
50Ω
40.2Ω
132Ω
40.2Ω
–5V
402Ω
402Ω
+5V
RL
400Ω
VO = 10VI
OPA843
–5V
Very Low Distortion Differential Driver
DIFFERENTIAL DISTORTION vs OUTPUT VOLTAGE
–85
GD = 10
RL = 400Ω
–90 F = 5MHz
–95
–100
2nd-Harmonic
–105
3rd-Harmonic
–110
1
Output Voltage Swing (Vp-p)
10
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.
All trademarks are the property of their respective owners.
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 © 2002-2003, Texas Instruments Incorporated
1 page  
TYPICAL CHARACTERISTICS: VS = ±5V (Cont.)
TA = +25°C, G = +5, RF = 402Ω, RG = 100Ω, and RL = 100Ω, unless otherwise noted.
5MHz HARMONIC DISTORTION vs LOAD RESISTANCE
–75
VO = 2Vp-p
–80 G = +5
–85
2nd-Harmonic
–90
–95
–100
–105
–110
100
3rd-Harmonic
150 200 250 300 350
Resistance (Ω)
See Figure 1
400 450 500
1MHz HARMONIC DISTORTION vs LOAD RESISTANCE
–75
VO = 5Vp-p
–80 G = +5
–85
–90
2nd-Harmonic
–95
–100
3rd-Harmonic
–105
See Figure 1
–110
100 150 200 250 300 350 400 450 500
Resistance (Ω)
HARMONIC DISTORTION vs FREQUENCY
–60
VO = 2Vp-p
G = +5
–70 RL = 200Ω
2nd-Harmonic
–80
–90
–100
See Figure 1
–110
0.1
3rd-Harmonic
1 10
Frequency (MHz)
100
HARMONIC DISTORTION vs OUTPUT VOLTAGE
–70
RL = 200Ω
–75 F = 5MHz
G = +5
–80
–85
2nd-Harmonic
–90
–95
–100
3rd-Harmonic
–105
See Figure 1
–110
0.1
1
Output Voltage Swing (Vp-p)
10
HARMONIC DISTORTION vs NONINVERTING GAIN
–70
2nd-Harmonic
–80
–90
–100
VO = 2Vp-p
RL = 200Ω
F = 5MHz
RF = 402Ω, RG Adjusted
–110
5
3rd-Harmonic
10 15
Gain (V/V)
See Figure 1
20
HARMONIC DISTORTION vs INVERTING GAIN
–75
–85
VO = 2Vp-p
RL = 200Ω
F = 5MHz
–95 RG = 50Ω, RF Adjusted
2nd-Harmonic
–105
–115
5
3rd-Harmonic
See Figure 2
10 15 20 25 30 35 40
Gain (–V/V)
OPA843
SBOS268A
www.ti.com
5
5 Page 
the 3rd-harmonic much lower. 2-tone 3rd-order intermodulation
terms will be much lower than most other solutions using the
circuit shown on the front page. The differential typical charac-
teristic curves also show that a 4Vp-p output will have
> 80dBc SFDR through 20MHz using this differential approach.
WIDE DYNAMIC RANGE “IF” AMPLIFIER
The OPA843 offers an attractive alternative to standard fixed-
gain IF amplifier stages. Narrowband systems will benefit from
the exceptionally high 2-tone 3rd-order intermodulation inter-
cept, as shown in the Typical Characteristics. Op amps with
high open-loop gain, like the OPA843, provide an intercept
that decreases with frequency along with the loop gain. The
OPA843’s 3rd-order intercept shows a decreasing intercept
with frequency. The OPA843’s intercept is > 30dBm up to
50MHz but improves to > 50dBm as the operating frequency
is reduced below 10MHz. Broadband systems will also benefit
from the very low even-order harmonics and intermodulation
components produced by the OPA843. Compared to standard
fixed-gain IF amplifiers, the OPA843 operating at IF’s below
50MHz provides much higher intercepts for its quiescent
power dissipation (200mW), superior gain accuracy, higher
reverse isolation, and lower I/O return loss. The noise figure
for the OPA843 will be higher than alternative fixed-gain
stages. If the application comes late in the amplifier chain with
significant gain in prior stages, this higher noise figure may be
acceptable. Figure 3 shows an example of a noninverting
configuration for the OPA843 used as an IF amplifier.
50Ω Source
0.01µF
PI
52.3Ω
+5V
Power-supply
decoupling not shown.
1kΩ OPA843
RS 50Ω Load
VO 50Ω
P0
RF
+5V 1kΩ
RG
144Ω
0.01µF
Gain
=
PI
PO
= 20log
1
2 1 +
RF
RG
dB
= 12dB
with
values shown
FIGURE 3. High Dynamic Range IF Amplifier.
The input signal and the gain resistor are AC coupled through
the 0.01µF blocking capacitors. This holds the DC input and
output operating point at ground independent of source im-
pedance and gain setting. The RG value in Figure 3 (144Ω),
sets the gain to the matched load at 12dB. Using standard 1%
tolerance resistors for RF and RG will hold the gain to a ±0.2dB
tolerance. This example will give a –3dB bandwidth of ap-
proximately 100MHz while maintaining gain flatness within
1dB through 50MHz. For narrowband IF’s in the 44MHz
region, this configuration of the OPA843 will show a 3rd-order
intercept of 33dBm while dissipating only 200mW (23dBm)
power from ±5V supplies.
PHOTODIODE TRANSIMPEDANCE AMPLIFIER
High Gain Bandwidth Product (GBP) and low input voltage
and current noise make the OPA843 an ideal wideband
transimpedance amplifier for low to moderate gains. Note
that unity-gain stability is not required for transimpedance
applications. Figure 4 shows an example photodiode ampli-
fier circuit. The key parameters of this design are the esti-
mated diode capacitance (CD) at the applied DC reverse bias
voltage (–VB), the desired transimpedance gain (RF), and the
GBP for the OPA843 (800MHz). With these three variables
set (and adding the OPA843’s parasitic input capacitance to
the value of CD to get CS), the feedback capacitor value (CF)
is selected to provide stability for the transimpedance fre-
quency response.
0.01µF
+5V
Power-supply decoupling
not shown.
10kΩ OPA843
VO = IDRF
–5V
RF
10kΩ
λ
ID CD
20pF
CF
0.75pF
–VB
FIGURE 3. High Dynamic Range IF Amplifier.
To achieve a maximally flat 2nd-order Butterworth frequency
response, the feedback pole should be set to:
1 = GBP
2πRF CF 4πRF CS
CS = CD + CI
(1)
Adding the OPA843’s common-mode and differential mode
input capacitances CI = (1.0 + 1.2)pF to the 20pF diode
source capacitance of Figure 4, and targeting a 10kΩ tran-
simpedance gain using the 800MHz GBP for the OPA843,
the required feedback pole frequency is 16.9MHz. This will
require a total feedback capacitance of 0.94pF. Typical
surface-mount resistors have a parasitic capacitance of
0.2pF, leaving the required 0.75pF value shown in Figure 4
to get the required feedback pole.
This will set the –3dB bandwidth according to:
F−3dB ≅
GBP Hz
2πRF CS
(2)
The example of Figure 4 will give approximately 24MHz
–3dB bandwidth using the 0.75pF feedback compensation.
OPA843
SBOS268A
www.ti.com
11
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet OPA843.PDF ] | |
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