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參數(shù)資料
| 型號： | OPA820IDR |
| 英文描述： | Unity-Gain Stable, Low-Noise, Voltage-Feedback Operational Amplifier |
| 中文描述： | 單位增益穩(wěn)定，低噪聲，電壓反饋運(yùn)算放大器 |
| 文件頁數(shù)： | 18/25頁 |
| 文件大?。?/td> | 427K |
| 代理商： | OPA820IDR |
"#$
SBOS303A JUNE 2004 REVISED JULY 2004
www.ti.com
18
6
0
6
12
18
24
30
36
42
48
54
60
66
72
Frequency (Hz)
G
100k
1M
10M
100M
Figure 11. High-Q 1MHz Bandpass Filter
Frequency Response
DESIGN-IN TOOLS
DEMONSTRATION BOARDS
Two PC boards are available to assist in the initial evaluation
of circuit performance using the OPA820 in its two package
styles. Both of these are available, free, as an unpopulated PC
board delivered with descriptive documentation. The
summary information for these boards is shown in the table
below.
PRODUCT
OPA820ID
PACKAGE
SO-8
BOARD PART
NUMBER
LITERATURE
REQUEST
NUMBER
DEM-OPA68xU
SBOU010
OPA820IDBV
SOT23-5
DEM-OPA6xxN
SBOU009
Go to the TI web site (www.ti.com) to request evaluation
boards in the OPA820 product folder.
MACROMODELS AND APPLICATIONS
SUPPORT
Computer simulation of circuit performance using SPICE is
often a quick way to analyze the performance of the OPA820
and its circuit designs. This is particularly true for video and R
F
amplifier circuits where parasitic capacitance and inductance
can play a major role on circuit performance. A SPICE model
for the OPA820 is available through the TI web page
(www.ti.com). The applications department is also available
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
the data sheet. These models do not attempt to distinguish
between the package types in their small-signal AC
performance.
OPERATING SUGGESTIONS
OPTIMIZING RESISTOR VALUES
Since the OPA820 is a unity-gain stable, 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 feed-
back resistor value should be between 200
and 1k
. Below
200
, the feedback network will present additional output
loading which can degrade the harmonic distortion perfor-
mance of the OPA820. Above 1k
, the typical parasitic
capacitance (approximately 0.2pF) across the feedback
resistor may cause unintentional band limiting in the amplifier
response. A direct short is suggested as a feedback for
A
V
= +1V/V.
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
consideration must be noted. R
G
becomes the input resistor
and therefore the load impedance to the driving source. If
impedance matching is desired, R
G
may be set equal to the
required termination value. However, at low inverting gains,
the resulting feedback resistor value can present a significant
load to the amplifier output. For example, an inverting gain of
2 with a 50
input matching resistor (= R
G
) would require a
100
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
specifications. 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
the phase margin approaches 90
°
, as it does in high-gain
configurations. At low signal gains, most amplifiers will exhibit
a more complex response with lower phase margin. The
OPA820 is optimized to give a maximally-flat, 2nd-order
Butterworth response in a gain of 2. In this configuration, the
OPA820 has approximately 64
°
of phase margin and will show
a typical 3dB bandwidth of 240MHz. When the phase margin
is 64
°
, the closed-loop bandwidth is approximately
√
2 greater
than the value predicted by dividing GBP by the noise gain.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OPA820IDRG4 | 功能描述:高速運(yùn)算放大器 Unity Gain Stable Lo Noise Vltg Feedback RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補(bǔ)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 |
| OPA820SKD3 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:UNITY-GAIN STABLE, LOW-NOISE, VOLTAGE-FEEDBACK OPERATIONAL AMPLIFIER |
| OPA820SKGD1 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:UNITY-GAIN STABLE, LOW-NOISE, VOLTAGE-FEEDBACK OPERATIONAL AMPLIFIER |
| OPA820SKGD3 | 功能描述:運(yùn)算放大器 - 運(yùn)放 Unity Gain Stable,Lo Noise,Vltg FB Op Amp RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| OPA827 | 制造商:BB 制造商全稱:BB 功能描述:Low-Noise, High-Precision, JFET-Input, OPERATIONAL AMPLIFIER |
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