參數(shù)資料
型號： OPA659IDBVR
廠商： Texas Instruments
文件頁數(shù)： 7/32頁
文件大小： 0K
描述： IC OPAMP JFET 650MHZ SGL SOT23-5
標(biāo)準(zhǔn)包裝： 3,000
放大器類型： J-FET
電路數(shù)： 1
轉(zhuǎn)換速率： 2550 V/µs
增益帶寬積： 350MHz
-3db帶寬： 650MHz
電流 - 輸入偏壓： 10pA
電壓 - 輸入偏移： 1000µV
電流 - 電源： 32mA
電流 - 輸出 / 通道： 70mA
電壓 - 電源，單路/雙路(±)： ±3.5 V ~ 6.5 V
工作溫度： -40°C ~ 85°C
安裝類型： 表面貼裝
封裝/外殼： SC-74A，SOT-753
供應(yīng)商設(shè)備封裝： SOT-23-5
包裝： 帶卷 (TR)
OPERATING SUGGESTIONS
Setting Resistor Values to Minimize Noise
Frequency Response Control
OPA659
R
T
I
BI
I
BN
e
N
e
O
R
G
R
F
4kTR
T
4kTR
F
4kT
R
G
e =
O
4kTR +(I
R ) +e
T
BN
T
N
2
+(I R ) +4kTR
BI
F
2
1+
R
F
G
1+
R
F
G
2
[
]
e
=
NI
4kTR +(I
R ) +e
T
BN
T
N
+
2
+
I R
NoiseGain
BI
F
4kTR
NoiseGain
F
2
www.ti.com ............................................................................................................................................ SBOS342B – DECEMBER 2008 – REVISED AUGUST 2009
Putting high resistor values into Equation 4 can
quickly dominate the total equivalent input-referred
noise. A source impedance on the noninverting input
The OPA659 provides a very low input noise voltage.
of 5k
adds a Johnson voltage noise term equal to
To take full advantage of this low input noise,
that of the amplifier alone (8.9nV/Hz). While the JFET
designers must pay careful attention to other possible
input of the OPA659 is ideal for high source
noise contributors. Figure 38 shows the op amp noise
impedance
applications
in
the
noninverting
analysis model with all the noise terms included. In
configuration of Figure 34 or Figure 35, both the
this model, all the noise terms are taken to be noise
overall bandwidth and noise are limited by high
voltage or current density terms in either nV/
√Hz or
source impedances.
pA/
√Hz.
Voltage-feedback op amps such as the OPA659
exhibit decreasing signal bandwidth as the signal gain
increases. In theory, this relationship is described by
the gain bandwidth product (GBP) shown in the
Electrical Characteristics. Ideally, dividing the GBP by
the noninverting signal gain (also called the Noise
Gain, or NG) can predict the closed-loop bandwidth.
In practice, this guideline is valid only when the phase
margin approaches 90 degrees, as it does in high
gain configurations. At low gains (with increased
feedback factors), most high-speed amplifiers exhibit
a more complex response with lower phase margins.
The OPA659 is compensated to give a maximally-flat
frequency response at a noninverting gain of +1 (see
Figure 38. Op Amp Noise Analysis Model
Figure 34). This compensation results in a typical
gain of +1 bandwidth of 650MHz, far exceeding that
The total output spot noise voltage can be computed
predicted by dividing the 350MHz GBP by 1.
as the square root of the squared contributing terms
Increasing the gain causes the phase margin to
to the output noise voltage. This computation adds all
approach 90 degrees and the bandwidth to more
the contributing noise powers at the output by
closely approach the predicted value of (GBP/NG). At
superposition, then takes the square root to arrive at
a gain of +10, the OPA659 shows the 35MHz
a spot noise voltage. Equation 3 shows the general
bandwidth predicted using the simple formula and the
form for this output noise voltage using the terms
typical GBP of 350MHz. Unity-gain stable op amps
shown in Figure 38.
such as the OPA659 can also be band-limited in
gains other than +1 by placing a capacitor across the
feedback resistor. For the noninverting configuration
of Figure 35, a capacitor across the feedback resistor
decreases the gain with frequency down to a gain of
(3)
+1. For instance, to band-limit a gain of +2 design to
Dividing this expression by the noise gain (GN = 1 +
20MHz, a 32pF capacitor can be placed in parallel
RF/RG) gives the equivalent input-referred spot noise
with the 249
feedback resistor. This configuration,
voltage at the noninverting input, as Equation 4
however, only decreases the gain from 2 to 1. Using
shows.
a feedback capacitor to limit the signal bandwidth is
more effective in the inverting configuration of
Figure 36. Adding that same capacitance to the
feedback of Figure 36 sets a pole in the signal
frequency response at 20MHz, but in this case it
(4)
continues to attenuate the signal gain to less than 1.
space
Note, however, that the noise gain of the circuit is
only reduced to a gain of 1 with the addition of the
space
feedback capacitor.
Copyright 2008–2009, Texas Instruments Incorporated
15
Product Folder Link(s): OPA659
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OPA659IDBVT 功能描述:高速運(yùn)算放大器 650MHz unity gain stable JFET Inp amp 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
OPA659IDRBR 功能描述:高速運(yùn)算放大器 650MHz unity gain stable JFET inp Amp 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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