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參數(shù)資料
| 型號： | VCA2616 |
| 英文描述： | Dual, Variable-Gain Amplifier with Low-Noise Preamp |
| 中文描述： | 雙路，可變增益放大器的低噪聲前置放大器 |
| 文件頁數(shù)： | 10/19頁 |
| 文件大?。?/td> | 389K |
| 代理商： | VCA2616 |
VCA2616, VCA2611
SBOS234E
10
www.ti.com
the circuit. This reduces the susceptibility to power-supply
variation, ripple, and noise. In addition, separate power
supply and ground connections are provided for each chan-
nel and for the reference circuitry, further reducing interchannel
crosstalk.
Further details regarding the design, operation, and use of
each circuit block are provided in the following sections.
LOW-NOISE PREAMPLIFIER (LNP)
—
DETAIL
The LNP is designed to achieve a low-noise figure, espe-
cially when employing active termination. Figure 4 is a
simplified schematic of the LNP, illustrating the differential
input and output capability. The input stage employs low
resistance local feedback to achieve stable low-noise, low-
distortion performance with very high input impedance. Nor-
mally, low noise circuits exhibit high power consumption as
a result of the large bias currents required in both input and
output stages. The LNP uses a patented technique that
combines the input and output stages such that they share
the same bias current. Transistors Q
4
and Q
5
amplify the
signal at the gate-source input of Q
4
, the +IN side of the LNP.
The signal is further amplified by the Q
1
and Q
2
stage, and
then by the final Q
3
and R
L
gain stage, which uses the same
bias current as the input devices Q
4
and Q
5
. Devices Q
6
through Q
10
play the same role for signals on the
–
IN side.
The differential gain of the LNP is given in Equation 1:
Gain
R
R
L
S
=
×
2
FIGURE 4. Schematic of the Low-Noise Preamplifier (LNP).
(1)
PGA OVERVIEW AND OVERALL DEVICE
CHARACTERISTICS
The differential output of the VCA attenuator is then amplified
by the PGA circuit block. This post-amplifier is programmed
by the same MGS bits that control the VCA attenuator,
yielding an overall swept-gain amplifier characteristic in which
the VCA
×
PGA gain varies from 0dB (unity) to a program-
mable peak gain of 24-, 27-, 30-, 33-, 36-, 39-, 42-, or 45dB.
The Gain vs VCA
CNTL
curve in the Typical Characteristics
shows the composite gain control characteristic of the entire
VCA2616. Setting VCA
CNTL
to 3.0V causes the digital MGS
gain control to step in 3dB increments. Setting VCA
CNTL
to 0V
causes all the MGS-controlled gain curves to converge at
one point. The gain at the convergence point is the LNP gain
less 6dB, because the measurement setup looks at only one
side of the differential PGA output, resulting in 6dB lower
signal amplitude.
ADDITIONAL FEATURES
—
OVERVIEW
Overload protection stages are placed between the attenua-
tor and the PGA, providing a symmetrically clipped output
whenever the input becomes large enough to overload the
PGA. A comparator senses the overload signal amplitude
and substitutes a fixed DC level to prevent undesirable
overload recovery effects. As with the previous stages, the
VCA is AC-coupled into the PGA. In this case, the coupling
time constant varies from 5
μ
s at the highest gain (45dB) to
59
μ
s at the lowest gain (25dB).
The VCA2616 includes a built-in reference, common to both
channels, to supply a regulated voltage for critical areas of
R
L
93
R
S1
105
Q
3
Q
4
Q
5
Q
2
Q
1
R
S2
34
R
S3
17
LNP
GS2
LNP
IN
P
LNP
IN
N
To Bias
Circuitry
LNP
GS1
LNP
GS3
R
L
93
COMP2A
V
DD
COMP1A
LNP
OUT
N
LNP
OUT
P
Buffer
Buffer
Q
8
Q
7
To Bias
Circuitry
Q
6
Q
9
Q
10
R
W
R
W
C
4.7pF
(External
Capacitor)
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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 工具用于評估:IR4302 工作電源電壓:13 V to 23 V |
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