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參數(shù)資料
| 型號(hào)： | VCA2616 |
| 英文描述： | Dual, Variable-Gain Amplifier with Low-Noise Preamp |
| 中文描述： | 雙路，可變?cè)鲆娣糯笃鞯牡驮肼暻爸梅糯笃?/td> |
| 文件頁(yè)數(shù)： | 12/19頁(yè) |
| 文件大?。?/td> | 389K |
| 代理商： | VCA2616 |
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VCA2616, VCA2611
SBOS234E
12
www.ti.com
FIGURE 5. Configurations for Active Feedback and Conven-
tional Cable Termination.
FIGURE 6. Noise Figure for Active Termination.
FIGURE 7. Noise Figure for Conventional Termination.
FIGURE 8. Low-Frequency LNP Time Constants.
the user-selected gain of the LNP, and R
IN
is the resulting
amplifier input impedance with active feedback. In this case,
unlike the conventional termination above, both the signal
voltage and the R
S
noise are attenuated by the same factor
of 2 (6dB) before being re-amplified by the A gain setting.
This avoids the extra 3dB degradation due to the square-root
effect described earlier, the key advantage of the active
termination technique.
This previous explanation ignored the input noise contribu-
tion of the LNP itself. Also, the noise contribution of the
feedback resistor must be included for a completely correct
analysis. The curves given in Figures 6 and 7 allow the
VCA2616 and VCA2611 user to compare the achievable
noise figure for active and conventional termination methods.
The left-most set of data points in each graph give the results
for typical 50
cable termination, showing the worst noise
figure but also the greatest advantage of the active feedback
method.
A switch, controlled by the FBSW
CNTL
signal on pin 45,
enables the user to reduce the feedback resistance by
adding an additional parallel component, connected between
the LNP
IN
P and SWFB terminals. The two different values of
feedback resistance will result in two different values of
active-feedback input resistance. Thus, the active-feedback
impedance can be optimized at two different LNP gain
settings. The switch is connected at the buffered output of
the LNP and has an ON resistance of approximately 1
.
When employing active feedback, the user should be careful
to avoid low-frequency instability or overload problems. Fig-
ure 8 illustrates the various low-frequency time constants.
R
F
A
R
IN
R
IN
=
R
S
R
S
R
S
= R
S
LNP
IN
R
F
1 + A
Active Feedback
A
Conventional Cable Termination
VCA NOISE = 3.8nV
√
Hz, LNP GAIN = 20dB
Source Impedance (
)
0
300
100
200
500
400
600
700
800
900 1000
N
9
8
7
6
5
4
3
2
1
0
6.0E-10
8.0E-10
1.0E-09
1.2E-09
1.4E-09
1.6E-09
1.8E-09
2.0E-09
LNP Noise
nV/
√
Hz
Source Impedance (
)
0
300
100
200
500
400
600
700
900 1000
800
N
14
12
10
8
6
4
2
0
VCA NOISE = 3.8nV
√
Hz, LNP GAIN = 20dB
LNP Noise
nV/
√
Hz
6.0E-10
8.0E-10
1.0E-09
1.2E-09
1.4E-09
1.6E-09
1.8E-09
2.0E-09
R
S
200k
C
C
C
F
0.001
μ
F
V
CM
R
F
44pF
Buffer
200k
V
CM
LNP
OUT
N
LNP
OUT
P
44pF
Gain
Stage
(VCA) LNP
Buffer
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| VCA2616EVM | 功能描述:放大器 IC 開發(fā)工具 VCA2616 Eval Mod RoHS:否 制造商:International Rectifier 產(chǎn)品:Demonstration Boards 類型:Power Amplifiers 工具用于評(píng)估:IR4302 工作電源電壓:13 V to 23 V |
| VCA2616YR | 功能描述:特殊用途放大器 Dual Variable Gain 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 |
| VCA2616YT | 功能描述:特殊用途放大器 Dual Variable Gain 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 |
| VCA2617 | 制造商:BB 制造商全稱:BB 功能描述:Dual, Variable Gain Amplifier |
| VCA2617EVM | 功能描述:放大器 IC 開發(fā)工具 VCA2617 Eval Mod RoHS:否 制造商:International Rectifier 產(chǎn)品:Demonstration Boards 類型:Power Amplifiers 工具用于評(píng)估:IR4302 工作電源電壓:13 V to 23 V |
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