參數(shù)資料
型號(hào)： OPA847IDBVT
英文描述： Wideband, Ultra-Low Noise, Voltage-Feedback
中文描述： 寬帶，超低噪聲，電壓反饋
文件頁(yè)數(shù)： 10/23頁(yè)
文件大?。?/td> 529K
代理商： OPA847IDBVT
OPA847
SBOS251C
10
www.ti.com
APPLICATIONS INFORMATION
WIDEBAND, NONINVERTING OPERATION
The OPA847 provides a unique combination of a very low
input voltage noise along with a very low distortion output
stage to give one of the highest dynamic range op amps
available. Its very high gain bandwidth product (GBP) can be
used to either deliver high signal bandwidths at high gains, or
to deliver very low distortion signals at moderate frequencies
and lower gains. To achieve the full performance of the
OPA847, careful attention to PC board layout and compo-
nent selection is required, as discussed in the following
sections of this data sheet.
Figure 1 shows the noninverting gain of a +20V/V circuit used
as the basis for most of the Typical Characteristics. Most of
the curves are characterized using signal sources with a
50
driving impedance and with measurement equipment
presenting a 50
load impedance. In Figure 1, the 50
shunt resistor at the V
I
terminal matches the source imped-
ance of the test generator, while the 50
series resistor at
the V
O
terminal provides a matching resistor for the mea-
surement equipment load. Generally, data sheet voltage
swing specifications are at the output pin (V
O
in Figure 1)
while output power specifications are at the matched 50
load. The total 100
load at the output combined with the
790
total feedback network load presents the OPA847 with
an effective output load of 89
for the circuit of Figure 1.
Voltage-feedback op amps, unlike current-feedback designs,
can use a wide range of resistor values to set their gain. The
circuit of Figure 1, and the specifications at other gains, use an
R
G
set to 39.2
and R
F
adjusted to get the desired gain. Using
this guideline ensures that the noise added at the output due
to the Johnson noise of the resistors does not significantly
increase the total over that due to the 0.85nV/
√
Hz
input
voltage noise for the op amp itself. This R
G
is suggested as
a good starting point for design. Other values are certainly
acceptable, if required by the design.
WIDEBAND, INVERTING GAIN OPERATION
There can be significant benefits to operating the OPA847 as
an inverting amplifier. This is particularly true when a matched
input impedance is required. Figure 2 shows the inverting
gain of a –40V/V circuit used as a starting point for the
Typical Characteristics showing inverting mode performance.
Driving this circuit from a 50
source, and constraining the gain
resistor (R
G
) to equal 50
, gives both a signal bandwidth and a noise
advantage. R
G
, in this case, acts as both the input termination resistor
and the gain setting resistor for the circuit. Although the signal gain
for the circuit of Figure 2 is double that for Figure 1, their noise gains
are nearly equal when the 50
source resistor is included. This has
the interesting effect of approximately doubling the equivalent GBP for
the amplifier. This can be seen by observing that the gain of –40
bandwidth of 240MHz shown in the Typical Characteristics implies a
gain bandwidth product of 9.6GHz, giving a far higher bandwidth at
a gain of –40 than at a gain of +40. While the signal gain from R
G
to
the output is –40,
the noise gain for bandwidth setting purposes is
1 + R
F
/(2 R
G
).
In the case of a –40V/V gain, using an R
G
= R
S
=
50
gives a noise gain = 1 + 2k
/100
= 21. This inverting gain of
–40V/V therefore has a frequency response that more closely
matches the gain of a +20 frequency response.
If the signal source is actually the low impedance output of
another amplifier, R
G
should be increased to be greater than
the minimum value allowed at the output for that amplifier
and R
F
adjusted to get the desired gain. It is critical for stable
operation of the OPA847 that this driving amplifier show a
very low output impedance through frequencies exceeding
the expected closed-loop bandwidth for the OPA847.
WIDEBAND, HIGH SENSITIVITY,
TRANSIMPEDANCE DESIGN
OPA847
+5V
–5V
–V
S
+V
S
50
V
O
V
DIS
V
I
50
+
0.1
μ
F
+
6.8
μ
F
6.8
μ
F
R
39.2
R
F
750
50
Source
50
Load
0.1
μ
F
FIGURE 1. Noninverting G = +20 Specification and Test Circuit.
FIGURE 2. Noninverting G = –40 Specification and Test Circuit.
OPA847
+5V
–5V
+V
S
–V
S
95.3
50
V
O
V
I
+
6.8
μ
F
0.1
μ
F
+
6.8
μ
F
0.1
μ
F
0.01
μ
F
R
F
2k
R
G
50
50
Source
50
Load
V
DIS
相關(guān)PDF資料
PDF描述
OPA847IDR Wideband, Ultra-Low Noise, Voltage-Feedback
OPAMP1EVB Op Amp Evaluation Board Manual SOT23, SC70, and SOIC8 Package
OPAMP3EVB Op Amp Evaluation Board Manual TSSOP−16 Package
OPB10100-SERIES Optoelectronic
OPB10510 8K, 1K X 8 2.5V SERIAL EE, IND, -40C to +85C, 8-TSSOP, TUBE
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
OPA847IDBVT 制造商:Texas Instruments 功能描述:OP AMP WIDEBAND VFB SOT-23-6 847
OPA847IDBVT 制造商:Texas Instruments 功能描述:Operational Amplifier (Op-Amp) IC
OPA847IDBVTG4 功能描述:高速運(yùn)算放大器 Wdebnd Ult-Lo 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(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
OPA847IDG4 功能描述:高速運(yùn)算放大器 Wdebnd Ult-Lo 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(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
OPA847IDR 功能描述:高速運(yùn)算放大器 Wdebnd Ult-Lo 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(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
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