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參數(shù)資料
| 型號： | VCA2618YT |
| 元件分類： | 可變增益放大器 |
| 英文描述： | Dual, Variable Gain Amplifier with Input Buffer |
| 中文描述： | 雙路，可變增益放大器輸入緩沖器 |
| 文件頁數(shù)： | 11/14頁 |
| 文件大?。?/td> | 326K |
| 代理商： | VCA2618YT |
VCA2618
SBOS254B
11
www.ti.com
PGA POST-AMPLIFIER
Figure 5 shows a simplified circuit diagram of the PGA block.
As stated before, the input to the PGA is AC coupled by an
internal capacitor. Provisions are made so that an external
capacitor can be placed in parallel with the internal capacitor,
thus lowering the usable low-frequency bandwidth. The low-
frequency bandwidth is set by the following equation:
1
2
π
500k
220pF
+
C
EXTERNAL
(
(
)
)
where C
EXTERNAL
is the external capacitor value in farads.
Care should be taken to avoid using too large a value of
capacitor, as this can increase the power-on delay time.
As described previously, the PGA gain is programmed with
the same MGS bits that control the VCA maximum attenua-
tion factor. Specifically, the maximum PGA gain at each
MGS setting is the inverse (reciprocal) of the maximum VCA
attenuation at that setting. Therefore, the VCA + PGA overall
gain will always be 0dB (unity) when the analog VCA
CNTL
input is set to 0V (the maximum attenuation for VCA). For
VCA
CNTL
= 3V (no attenuation), the VCA + PGA gain will be
controlled by the programmed PGA gain (25dB to 43dB in
3dB steps). For clarity, the gain and attenuation factors are
detailed in Table I.
The PGA architecture converts the single-ended signal from
the VCA into a differential signal. Low input noise was also
a requirement of the PGA design due to the large amount of
signal attenuation that can be asserted before the PGA. At
minimum VCA attenuation (used for small input signals), the
MGS
SETTING
ATTENUATOR GAIN
VCA
CNTL
= 0V to 3V
ATTENUATOR +
DIFFERENTIAL PGA GAIN
000
001
010
011
100
101
110
111
Not Valid
–25dB to 0dB
–28dB to 0dB
–31dB to 0dB
–34dB to 0dB
–37dB to 0dB
–40dB to 0dB
–43dB to 0dB
Not Valid
0dB to 25dB
0dB to 28dB
0dB to 31dB
0dB to 34dB
0dB to 37dB
0dB to 40dB
0dB to 43dB
R
S1
R
L
R
S2
VCA
OUT
P
+In
Q
11
Q
3
Q
4
Q
5
Q
1
V
CM
Q
2
VCA
OUT
N
Q
9
Q
8
Q
13
Q
14
Q
7
Q
6
Q
12
V
DD
V
CM
R
L
Q
10
–In
To Bias
Circuitry
To Bias
Circuitry
FIGURE 5. Simplified Block Diagram of the PGA Section with the VCA2618.
TABLE I. MGS Settings.
input buffer noise dominates; at maximum VCA attenuation
(large input signals), the PGA noise dominates. Note that if
the PGA output is used single-ended, the apparent gain will
be 6dB lower.
LAYOUT CONSIDERATIONS
The VCA2618 is an analog amplifier capable of high gain.
When working on a PCB layout for the VCA2618, it is
recommended to utilize a solid ground plane that is con-
nected to analog ground. This helps to maximize the noise
performance of the VCA2618.
Adequate power-supply decoupling must be used in order to
achieve the best possible performance. Decoupling capaci-
tors on the VCA
CNTL
voltage should also be used to help
minimize noise. Recommended values can be obtained from
the layout diagram of Figure 6.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| VCA2619 | 制造商:BB 制造商全稱:BB 功能描述:Dual, Variable Gain Amplifier with Input Buffer |
| VCA2619EVM | 功能描述:放大器 IC 開發(fā)工具 VCA2619 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 |
| VCA2619YR | 功能描述:特殊用途放大器 Dual Variable Gain w/Input Buffer 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 |
| VCA2619YT | 功能描述:特殊用途放大器 Dual Variable Gain w/Input Buffer 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 |
| VCA3 | 制造商:VECTRON 制造商全稱:Vectron International, Inc 功能描述:3.3, 5.0 volt CMOS Oscillator |
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