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參數(shù)資料
| 型號： | OPA843IDR |
| 元件分類： | 運算放大器 |
| 英文描述： | Wideband, Low Distortion, Medium Gain, Voltage-Feedback OPERATIONAL AMPLIFIER |
| 中文描述： | 寬帶，低失真，中等增益，電壓反饋運算放大器 |
| 文件頁數(shù)： | 13/22頁 |
| 文件大?。?/td> | 377K |
| 代理商： | OPA843IDR |
OPA843
SBOS268A
13
www.ti.com
MACROMODELS AND APPLICATIONS SUPPORT
Computer simulation of circuit performance using SPICE is
often a quick way to analyze the performance of the OPA843
and its circuit designs. This is particularly true for video and
RF amplifier circuits where parasitic capacitance and induc-
tance can play a major role on circuit performance. A SPICE
model for the OPA843 is available through the TI web page
(http://www.ti.com). The applications department is also avail-
able for design assistance. These models predict typical
small-signal AC, transient steps, DC performance, and noise
under a wide variety of operating conditions. The models
include the noise terms found in the electrical specifications
of this data sheet. These models do not attempt to distin-
guish between the package types in their small-signal AC
performance.
OPERATING SUGGESTIONS
OPTIMIZING RESISTOR VALUES
Since the OPA843 is a voltage-feedback op amp, a wide
range of resistor values may be used for the feedback and
gain setting resistors. The primary limits on these values are
set by dynamic range (noise and distortion) and parasitic
capacitance considerations. Usually, the feedback resistor
value should be between 200
and 1k
. Below 200
, the
feedback network will present additional output loading that
can degrade the harmonic distortion performance of the
OPA843. Above 1k
, the typical parasitic capacitance (ap-
proximately 0.2pF) across the feedback resistor may cause
unintentional band limiting in the amplifier response.
A good rule of thumb is to target the parallel combination of
R
F
and R
G
(see Figure 1) to be less than about 200
. The
combined impedance R
F
|| R
G
interacts with the inverting
input capacitance, placing an additional pole in the feedback
network, and thus a zero in the forward response. Assuming
a 2pF total parasitic on the inverting node, holding R
F
|| R
G
< 200
will keep this pole above 400MHz. By itself, this
constraint implies that the feedback resistor R
F
can increase
to several k
at high gains. This is acceptable as long as the
pole formed by R
F
and any parasitic capacitance appearing
in parallel is kept out of the frequency range of interest.
In the inverting configuration, an additional design consider-
ation must be noted. R
G
becomes the input resistor and,
therefore, the load impedance to the driving source. If imped-
ance matching is desired, R
G
may be set equal to the
required termination value. However, at low inverting gains
the resultant feedback resistor value can present a signifi-
cant load to the amplifier output. For example, an inverting
gain of
–
4 with a 50
input matching resistor (= R
G
) would
require a 200
feedback resistor, which would contribute to
output loading in parallel with the external load. In such a
case, it would be preferable to increase both the R
F
and R
G
values, and then achieve the input matching impedance with
a third resistor to ground, see Figure 2. The total input
impedance becomes the parallel combination of R
G
and the
additional shunt resistor.
BANDWIDTH vs GAIN
Voltage-feedback op amps exhibit decreasing closed-loop
bandwidth as the signal gain is increased. In theory, this
relationship is described by the GBP shown in the electrical
characteristics. Ideally, dividing GBP by the noninverting
signal gain (also called the Noise Gain, or NG) will predict the
closed-loop bandwidth. In practice, this only holds true when
R
5
1.2k
R
1
120
R
2
1.2k
OPA843
R
F
1.2k
–
5V
V
EE
+5V
V
CC
OPA843
–
5V
V
EE
+5V
V
CC
R
LOAD
1k
R
G
V
OUT
V
IN
C
41.125pF
R
4
600
C
5.2pF
Power-supply
decoupling not shown.
Frequency
100kHz
1MHz
10MHz
100MHz
1GHz
(
40
20
0
–
20
–
40
FIGURE 8. Adjustable Equalizer.
FIGURE 9. Equalizer Plot, Multiple Settings.
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PDF描述 |
|---|---|
| OPA843 | Wideband, Low Distortion, Medium Gain, Voltage-Feedback OPERATIONAL AMPLIFIER |
| OPA843IDBVR | Wideband, Low Distortion, Medium Gain, Voltage-Feedback OPERATIONAL AMPLIFIER |
| OPA843IDBVT | Wideband, Low Distortion, Medium Gain, Voltage-Feedback OPERATIONAL AMPLIFIER |
| OPA860 | Wide Bandwidth OPERATIONAL TRANSCONDUCTANCE AMPLIFIER (OTA) and BUFFER |
| OPA860ID | Wide Bandwidth OPERATIONAL TRANSCONDUCTANCE AMPLIFIER (OTA) and BUFFER |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OPA843IDRG4 | 功能描述:高速運算放大器 Wideband Lo-Distort Med Gain Vltg Feedbk RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補償電壓:0.5 mV 轉(zhuǎn)換速度:55 V/us 工作電源電壓:36 V 電源電流:7.5 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| OPA846 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Wideband, Low-Noise, Voltage-Feedback OPERATIONAL AMPLIFIER |
| OPA846ID | 功能描述:高速運算放大器 Wideband Low Noise Voltage Feedback RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補償電壓:0.5 mV 轉(zhuǎn)換速度:55 V/us 工作電源電壓:36 V 電源電流:7.5 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| OPA846ID | 制造商:Texas Instruments 功能描述:OP AMP WIDEBAND VFB SOIC8 846 |
| OPA846IDBVR | 功能描述:高速運算放大器 Wideband Low Noise Voltage Feedback RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補償電壓:0.5 mV 轉(zhuǎn)換速度:55 V/us 工作電源電壓:36 V 電源電流:7.5 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
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