參數(shù)資料
型號(hào)： THS4504DGKR
廠商： Texas Instruments, Inc.
元件分類： 運(yùn)動(dòng)控制電子
英文描述： WIDEBAND, LOW-DISTORTION, FULLY DIFFERENTIAL AMPLIFIERS
中文描述： 寬帶，低失真，全差分放大器
文件頁(yè)數(shù)： 27/38頁(yè)
文件大?。?/td> 1094K
代理商： THS4504DGKR
www.ti.com
OIP
3
P
O
IMD
3
2
where
P
O
10 log
V
2
Pdiff
0.001
2R
L
(10)
(11)
IMD
3
OIP
3
IIP
3
3X
P
IN
(dBm)
1X
P
OUT
(dBm)
P
O
P
S
10
20
30
40
50
60
0
20
40
60
80
100
O
f Frequency MHz
0
Normalized to 50
Gain = 1
R
f
= 499
V
O
= 2 V
PP
V
S
=
±
5 V
200 kHz Tone Spacing
R
L
= 800
Normalized to 200
3
AN ANALYSIS OF NOISE IN FULLY
DIFFERENTIAL AMPLIFIERS
Noise analysis in fully differential amplifiers is anal-
ogous to noise analysis in single-ended amplifiers.
The same concepts apply. Below, a generic circuit
diagram consisting of a voltage source, a termination
resistor, two gain setting resistors, two feedback
resistors, and a fully differential amplifier is shown,
including all the relevant noise sources. From this
circuit, the noise factor (F) and noise figure (NF) are
calculated.
The
figures
scaling factor for each of the noise sources in two
different cases. The first case includes the termin-
ation resistor, and the second, simplified case as-
THS4504
THS4505
SLOS363C–AUGUST 2002–REVISED MARCH 2004
#IMPLIED. NOTE: P
o
is the output power of a
single tone, R
L
is the differential load resist-
ance, and V
P(diff)
is the differential peak
voltage for a single tone.
As can be seen in the equation, when a higher
impedance is used, the same level of intermodulation
distortion performance results in a lower intercept
point. Therefore, it is important to comprehend the
impedance seen by the output of the fully differential
amplifier when selecting a minimum intercept point.
The graphic below shows the relationship between
the strict definition of an intercept point with a
normalized, or equivalent, intercept point for the
THS4502.
Figure 86.
Due to the intercept point's ease of use in system
level calculations for receiver chains, it has become
the
specification
of
choice
tion-related design decisions. Traditionally, these sys-
tems use primarily class-A, single-ended RF ampli-
fiers as gain blocks. These RF amplifiers are typically
designed to operate in a 50-
environment, just like
the rest of the receiver chain. Since intercept points
are given in dBm, this implies an associated im-
pedance (50
).
However, with a fully differential amplifier, the output
does not require termination as an RF amplifier
would. Because closed-loop amplifiers deliver signals
to their outputs regardless of the impedance present,
it is important to comprehend this when evaluating
the intercept point of a fully differential amplifier. The
THS4500 series of devices yields optimum distortion
performance when loaded with 200
to 1 k
, very
similar to the input impedance of an analog-to-digital
converter over its input frequency band. As a result,
terminating the input of the ADC to 50
can actually
be detrimental to system performance.
for
guiding
distor-
Figure 87.
Comparing specifications between different device
types becomes easier when a common impedance
level is assumed. For this reason, the intercept points
on the THS4500 family of devices are reported
normalized to a 50-
load impedance.
This discontinuity between open-loop, class-A ampli-
fiers and closed-loop, class-AB amplifiers becomes
apparent when comparing the intercept points of the
two types of devices. Equation 10 gives the definition
of an intercept point, relative to the intermodulation
distortion.
indicate
the
appropriate
27
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參數(shù)描述
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THS4504DGN 功能描述:特殊用途放大器 Wideband Lo-Noise Lo-Distortion RoHS:否 制造商:Texas Instruments 通道數(shù)量:Single 共模抑制比（最小值）: 輸入補(bǔ)償電壓: 工作電源電壓:3 V to 5.5 V 電源電流:5 mA 最大功率耗散: 最大工作溫度:+ 70 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-20 封裝:Reel
THS4504DGN 制造商:Texas Instruments 功能描述:IC OP-AMP DIFF 210MHZ SGL 8MSOP
THS4504DGNG4 功能描述:特殊用途放大器 Wideband Lo-Noise Lo-Distortion RoHS:否 制造商:Texas Instruments 通道數(shù)量:Single 共模抑制比（最小值）: 輸入補(bǔ)償電壓: 工作電源電壓:3 V to 5.5 V 電源電流:5 mA 最大功率耗散: 最大工作溫度:+ 70 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-20 封裝:Reel
THS4504DGNR 功能描述:特殊用途放大器 Wideband Lo-Noise Lo-Distortion RoHS:否 制造商:Texas Instruments 通道數(shù)量:Single 共模抑制比（最小值）: 輸入補(bǔ)償電壓: 工作電源電壓:3 V to 5.5 V 電源電流:5 mA 最大功率耗散: 最大工作溫度:+ 70 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-20 封裝:Reel
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