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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)： | 9/14頁 |
| 文件大小： | 326K |
| 代理商： | VCA2618YT |
VCA2618
SBOS254B
9
www.ti.com
OVERVIEW
The VCA2618 is a dual-channel, VGA consisting of three
primary blocks, an Input Buffer, a VCA, and a PGA. All
stages are AC coupled, with the coupling into the PGA stage
being made variable by placing an external capacitor be-
tween the C
P1
and C
P2
pins. This will be discussed further in
the PGA section. By using the internal coupling into the PGA,
the result is a high-pass filter characteristic with cutoff at
approximately 75kHz. The output PGA naturally rolls off at
around 30MHz, making the usable bandwidth of the VCA2618
between 75kHz and 30MHz.
FIGURE 2. Swept Attenuator Characteristic.
0
–25
V
–43
Control Voltage
0
Maximum Attenuation
Minimum Attenuation
3.0V
R
S
Q
1A
A1
B1
B2
V
CM
Input
Output
Q
1B
Q
2A
A2
Q
2B
Q
3A
A3
Q
3B
Q
4A
A4
Q
4B
Q
5A
A5
Q
5B
FIGURE 3. Programmable Attenuator Section.
VCA
Buffer
Buffer
Channel A
Input
VCA
Control
PGA
Channel A
Output
Maximum
Gain
Select
MGS
Analog
Control
VCA
Channel B
Input
PGA
Channel B
Output
FIGURE 1. Simplified Block Diagram of the VCA2618.
INPUT BUFFER
The input buffer is a unity gain amplifier (gain of +1) with a
bandwidth of 100MHz with an input resistance of approxi-
mately 600k
. The input buffer isolates the circuit driving the
VCA2618 inputs from the internal VCA block, which would
present a varying impedance to the input circuitry. To allow
symmetrical operation of the input buffer, the input to the
buffer must be AC coupled through an external capacitor.
The recommended value of the capacitor is 0.01μF. It should
be noted that if the capacitor value were increased, the
power-on time of the VCA2618 would be increased. If a
decrease in the power-on time is needed, the value can be
decreased to no less than 100pF.
VOLTAGE-CONTROLLED ATTENUATOR
The magnitude of the VCA input signal from the input buffer
is reduced by a programmable attenuation factor, set by the
analog VCA Control Voltage (VCA
CNTL
) at pin 24. The maxi-
mum attenuation is programmable by using the three MGS
bits (pins 21, 22, and 23). Figure 2 illustrates this dual-adjust
characteristic.
The MGS bits adjust the overall range of attenuation and
maximum gain while the VCA
CNTL
voltage adjusts the actual
attenuation factor. At any given maximum gain setting, the
analog variable gain characteristic is linear in dB as a
function of the control voltage, and is created as a piecewise
approximation of an ideal dB-linear transfer function. The
VCA control circuitry is common to both channels of the
VCA2618. The range for the VCA
CNTL
input spans from 0V to
3V. Although overdriving the VCA
CNTL
input above the rec-
ommended 3V maximum will not damage the part, this
condition should be avoided.
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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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