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| 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，電壓反饋運算放大器 |
| 文件頁數(shù)： | 13/25頁 |
| 文件大?。?/td> | 427K |
| 代理商： | OPA820IDR |
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SBOS303A JUNE 2004 REVISED JULY 2004
www.ti.com
13
APPLICATIONS INFORMATION
WIDEBAND VOLTAGE-FEEDBACK
OPERATION
The combination of speed and dynamic range offered by the
OPA820 is easily achieved in a wide variety of application
circuits, providing that simple principles of good design
practice are observed. For example, good power-supply
decoupling, as shown in Figure 1, is essential to achieve the
lowest possible harmonic distortion and smooth frequency
response.
Proper PC board layout and careful component selection will
maximize the performance of the OPA820 in all applications,
as discussed in the following sections of this data sheet.
Figure 1 shows the gain of +2 configuration used as the basis
for most of the typical characteristics. Most of the curves were
characterized using signal sources with 50
driving
impedance and with measurement equipment presenting
50
load impedance. In Figure 1, the 50
shunt resistor at the
V
I
terminal matches the source impedance of the test
generator while the 50
series resistor at the V
O
terminal
provides a matching resistor for the measurement equipment
load. Generally, data sheet specifications refer to the voltage
swings at the output pin (V
O
in Figure 1). The 100
load,
combined with the 804
total feedback network load,
presents the OPA820 with an effective load of approximately
90
in Figure 1.
OPA820
+5V
5V
V
S
+V
S
R
S
50
V
O
V
IN
50
+
2.2
μ
F
+
2.2
μ
F
0.1
μ
F
R
G
402
R
F
402
50
Source
50
Load
0.1
μ
F
Figure 1. Gain of +2, High-Frequency Application
and Characterization Circuit
WIDEBAND INVERTING OPERATION
Operating the OPA820 as an inverting amplifier has several
benefits and is particularly useful when a matched 50
source
and input impedance is required. Figure 2 shows the inverting
gain of 1 circuit used as the basis of the inverting mode
typical characteristics.
OPA820
+5V
5V
50
V
O
V
I
+
0.1
μ
F
2.2
μ
F
+
0.1
μ
F
2.2
μ
F
R
57.6
R
T
205
R
F
402
50
Source
50
Load
0.01
μ
F
R
G
402
Figure 2. Inverting G = 1 Specifications and Test
Circuit
In the inverting case, just the feedback resistor appears as
part of the total output load in parallel with the actual load. For
the 100
load used in the typical characteristics, this gives a
total load of 80
in this inverting configuration. The gain
resistor is set to get the desired gain (in this case 402
for a
gain of 1) while an additional input matching resistor (R
M
) can
be used to set the total input impedance equal to the source
if desired. In this case, R
M
= 57.6
in parallel with the 402
gain setting resistor gives a matched input impedance of 50
.
This matching is only needed when the input needs to be
matched to a source impedance, as in the characterization
testing done using the circuit of Figure 2.
The OPA820 offers extremely good DC accuracy as well as
low noise and distortion. To take full advantage of that DC
precision, the total DC impedance looking out of each of the
input nodes must be matched to get bias current cancellation.
For the circuit of Figure 2, this requires the 205
resistor
shown to ground on the noninverting input. The calculation for
this resistor includes a DC-coupled 50
source impedance
along with R
G
and R
M
. Although this resistor will provide
cancellation for the bias current, it must be well decoupled
(0.01
μ
F in Figure 2) to filter the noise contribution of the
resistor and the input current noise.
As the required R
G
resistor approaches 50
at higher gains,
the bandwidth for the circuit in Figure 2 will far exceed the
bandwidth at that same gain magnitude for the noninverting
circuit of Figure 1. This occurs due to the lower
noise gain
for
the circuit of Figure 2 when the 50
source impedance is
included in the analysis. For instance, at a signal gain of 10
(R
G
= 50
, R
M
= open, R
F
= 499
) the noise gain for the
circuit of Figure 2 will be 1 + 499
/(50
+ 50
) = 6 as a result
of adding the 50
source in the noise gain equation. This
gives considerable higher bandwidth than the noninverting
gain of +10. Using the 240MHz gain bandwidth product for the
OPA820, an inverting gain of 10 from a 50
source to a 50
R
G
gives 55MHz bandwidth, whereas the noninverting gain of
+10 gives 30MHz.
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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:運算放大器 - 運放 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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