參數(shù)資料
型號： THS4271D
廠商： TEXAS INSTRUMENTS INC
元件分類： 音頻／視頻放大
英文描述： 1 CHANNEL, VIDEO AMPLIFIER, PDSO8
封裝： PLASTIC, SOIC-8
文件頁數(shù)： 20/48頁
文件大?。?/td> 1227K
代理商： THS4271D
_
+
Rf
4kT = 1.6E-20J
at 290K
THS4271/THS4275
IBN
EO
ERF
RS
ERS
IBI
Rg
ENI
4kTRS
4kT
Rg
4kTRf
E
O +
E 2
NI
) IBNRS
2
) 4kTRS NG
2 ) IBIRf
2
) 4kTRfNG
E
O
+
E 2
NI
) IBNRS
2
) 4kTRS )
I
BIRf
NG
2
)
4kTR
f
NG
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
1 M
10 M
100 M
f - Frequency - Hz
Normalized
Gain
-
dB
FREQUENCY RESPONSE
vs
CAPACITIVE LOAD
RL = 499
VS =±5 V
R(ISO) = 25 CL = 10 pF
R(ISO) = 15 CL = 100 pF
R(ISO) = 10 CL = 50 pF
www.ti.com
SLOS397F – JULY 2002 – REVISED OCTOBER 2009
additional pole in the signal path that can decrease
the phase margin. When the primary considerations
are frequency response flatness, pulse response
fidelity, or distortion, the simplest and most effective
solution is to isolate the capacitive load from the
feedback loop by inserting a series isolation resistor
between the amplifier output and the capacitive load.
This does not eliminate the pole from the loop
response, but rather shifts it and adds a zero at a
higher frequency. The additional zero acts to cancel
the phase lag from the capacitive load pole, thus
increasing the phase margin and improving stability.
The Typical Characteristics show the recommended
isolation resistor vs capacitive load and the resulting
Figure 87. Noise Analysis Model
frequency response at the load. Parasitic capacitive
loads greater than 2 pF can begin to degrade the
The total output spot noise voltage can be computed
performance of the THS4271. Long PCB traces,
as the square of all square output noise voltage
unmatched cables, and connections to multiple
contributors. Equation 4 shows the general form for
devices can easily cause this value to be exceeded.
the output noise voltage using the terms shown in
Always consider this effect carefully, and add the
recommended series resistor as close as possible to
the THS4271 output pin (see the Board Layout
Guidelines section).
(4)
The criterion for setting this R(ISO) resistor is a
maximum bandwidth, flat frequency response at the
Dividing this expression by the noise gain [NG=(1+
load. For a gain of +2, the frequency response at the
Rf/Rg)] gives the equivalent input-referred spot noise
output pin is already slightly peaked without the
voltage at the noninverting input, as shown in
capacitive load, requiring relatively high values of
R(ISO) to flatten the response at the load. Increasing
the noise gain also reduces the peaking.
(5)
Evaluation of these two equations for the circuit and
component values shown in Figure 75 will give a total
output spot noise voltage of 12.2 nV/
√Hz and a total
equivalent input spot noise voltage of 6.2 nV/
√Hz.
This includes the noise added by the resistors. This
total input-referred spot noise voltage is not much
higher
than
the
3-nV/
√Hz
specification
for
the
amplifier voltage noise alone.
Driving Capacitive Loads
One of the most demanding, and yet very common,
load conditions for an op amp is capacitive loading.
Often, the capacitive load is the input of an A/D
converter, including additional external capacitance,
which may be recommended to improve A/D linearity.
Figure 88. Isolation Resistor Diagram
A high-speed, high open-loop gain amplifier like the
THS4271 can be very susceptible to decreased
stability and closed-loop response peaking when a
capacitive load is placed directly on the output pin.
When the amplifier open-loop output resistance is
considered,
this
capacitive
load
introduces
an
Copyright 2002–2009, Texas Instruments Incorporated
27
Product Folder Link(s): THS4271 THS4275
相關(guān)PDF資料
PDF描述
THS4271DRBT 1 CHANNEL, VIDEO AMPLIFIER, PDSO8
THS4271DGKR 1 CHANNEL, VIDEO PREAMPLIFIER, PDSO8
THS4271DGK 1 CHANNEL, VIDEO PREAMPLIFIER, PDSO8
THS4271DG4 1 CHANNEL, VIDEO PREAMPLIFIER, PDSO8
THS4271DGKRG4 1 CHANNEL, VIDEO PREAMPLIFIER, PDSO8
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
THS4271D 制造商:Texas Instruments 功能描述:OP AMP HIGH SPEED VFB 4271 SOIC8
THS4271DG4 功能描述:高速運算放大器 Super-Fast Ultra-Low Distortion 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
THS4271DGK 功能描述:高速運算放大器 Super-Fast Ultra-Low Distortion 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
THS4271DGKG4 功能描述:高速運算放大器 Super-Fast Ultra-Low Distortion 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
THS4271DGKR 功能描述:高速運算放大器 Super-Fast Ultra-Low Distortion 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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