參數(shù)資料
型號： OPA2652U2K5
英文描述： Dual, 700MHz, Voltage-Feedback OPERATIONAL AMPLIFIER
中文描述： 雙通道，700MHz的，電壓反饋運算放大器
文件頁數(shù)： 15/20頁
文件大?。?/td> 297K
代理商： OPA2652U2K5
www.ti.com
DC Accuracy and Offset Control
1/2
OPA2652
4kTR
F
4kTR
S
4kT
R
G
R
G
R
F
R
S
I
BI
E
O
I
BN
4kT = 1.6 x 10
J
-
20
at 290 K
°
E
RS
E
NI
NG
V
OS(MAX)
1.94
14.0mV
noninverting signal gain
R
F
I
OS(MAX)
402
7.0mV
1.0 A
NG
E
N
E
NI
2
I
BN
R
S
2
4kTR
S
I
BI
R
F
NG
2
4kTR
F
NG
E
O
E
NI
2
I
BN
R
S
2
4kTR
S
NG
2
(I
BI
R
F
)
2
4kTR
F
NG
OPA2652
SBOS125A–JUNE 2000–REVISED MAY 2006
The balanced input stage of a wideband voltage
feedback op amp allows good output DC accuracy in
a
wide
variety
of
applications.
high-speed input stage does require relatively high
input bias current (typically 4
μ
A out of each input
terminal), the close matching between them may be
used to significantly reduce the output DC error
caused by this current. This reduction is done by
matching the DC source resistances appearing at the
two inputs. This matching reduces the output DC
error resulting from the input bias currents to the
offset current times the feedback resistor. Evaluating
the configuration of
Figure 28
, using worst-case
+25
°
C input offset voltage and current specifications,
gives a worst-case output offset voltage equal to:
Although
the
Figure 35. Op Amp Noise Analysis Model
The total output spot noise voltage can be computed
as the square root of the sum of all squared output
noise voltage contributors.
Equation 1
shows the
general form for the output noise voltage using the
terms shown in
Figure 35
.
A fine scale output offset null, or DC operating point
adjustment, is often required. Numerous techniques
are available for introducing DC offset control into an
op amp circuit. Most of these techniques add a DC
current through the feedback resistor. In selecting an
offset trim method, one key consideration is the
impact
on
the
desired
response. If the signal path is intended to be
noninverting, the offset control is best applied as an
inverting summing signal to avoid interaction with the
signal source. If the signal path is intended to be
inverting,
applying
the
noninverting input may be considered. However, the
DC offset voltage on the summing junction sets up a
DC current back into the source which must be
considered. Applying an offset adjustment to the
inverting op amp input can change the noise gain
and frequency response flatness. For a DC-coupled
inverting amplifier,
Figure 36
shows one example of
an offset adjustment technique that has minimal
impact on the signal frequency response. In this
case, the DC offset current is brought into the
inverting input node through resistor values that are
much larger than the signal path resistors. This
configuration ensures that the adjustment circuit has
minimal effect on the loop gain, and therefore on the
frequency response as well.
(1)
Dividing this expression by the noise gain (NG = 1 +
R
F
/R
G
) gives the equivalent input-referred spot noise
voltage at the noninverting input, as shown in
Equation 2
.
signal
path
frequency
(2)
offset
control
to
the
Evaluating these two equations for the OPA2652
circuit and component values shown in
Figure 28
gives a total output spot noise voltage of 17nV/
√
Hz
and a total equivalent input spot noise voltage of
8.4nV/
√
Hz. This noise includes the noise added by
the bias current cancellation resistor (205
) on the
noninverting input. This total input-referred spot
noise voltage is only slightly higher than the 8nV/
√
Hz
specification for the op amp voltage noise alone.
This result will be the case as long as the
impedances appearing at each op amp input are
limited to the previously recommend maximum value
of
300
.
Keeping
both
noninverting input source impedance less than 300
satisfies both noise and frequency response flatness
considerations. Since the resistor-induced noise is
relatively negligible, additional capacitive decoupling
across the bias current cancellation resistor (R
B
) for
the inverting op amp configuration of
Figure 29
is not
required.
(R
||
R
)
and
the
15
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
OPA2652UG4 功能描述:高速運算放大器 Dual 700MHz 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
OPA2658E 制造商:Rochester Electronics LLC 功能描述:- Bulk
OPA2658E1250 制造商:Rochester Electronics LLC 功能描述:- Bulk
OPA2658P 功能描述:高速運算放大器 Dual Wideband 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
OPA2658U 功能描述:高速運算放大器 Dual Wideband 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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