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参数资料
| 型号： | VCA2614Y/2K |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 模拟信号调理 |
| 英文描述： | SPECIALTY ANALOG CIRCUIT, PQFP32 |
| 封装： | PLASTIC, TQFP-32 |
| 文件页数： | 18/18页 |
| 文件大小： | 519K |
| 代理商： | VCA2614Y/2K |
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VCA2614
OVERVIEW
The VCA2614 is a dual-channel, VGA consisting of three
primary blocks: an Input Buffer, a VCA, and a PGA (as
shown in Figure 1). All stages are AC-coupled with the
coupling into the PGA stage being made variable by placing
an external capacitor between the CP1 and CP2 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 charac-
teristic with cutoff at approximately 75kHz. The output PGA
naturally rolls off at around 40MHz, making the usable
bandwidth of the VCA2614 between 75kHz and 40MHz.
FIGURE 2. Swept Attenuator Characteristic.
0
–24.1
VCA
Attenuation
(dB)
–40
Control Voltage
0
Maximum Attenuation
Minimum Attenuation
3.0V
R
S
Q
1A
A1
B1
V
CM
INPUT
OUTPUT
PROGRAMMABLE ATTENUATOR SECTION
B2
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
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 VCA2614.
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
VCA2614 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 0.01
F. It should
be noted that if the capacitor value were increased, the
power-on time of the VCA2614 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 (VCACNTL) 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 VCACNTL 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, see
Figure 4. The VCA control circuitry is common to both
channels of the VCA2614. The range for the VCACNTL input
spans from 0V to 3V. Although overdriving the VCACNTL input
above the recommended 3V maximum will not damage the
part, this condition should be avoided.
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| VCA2615 | 制造商:BB 制造商全称:BB 功能描述:Dual, Variable Gain Amplifier |
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| VCA2615RGZR | 功能描述:特殊用途放大器 2-Channel Variable Gain Amplifier RoHS:否 制造商:Texas Instruments 通道数量:Single 共模抑制比（最小值）: 输入补偿电压: 工作电源电压:3 V to 5.5 V 电源电流:5 mA 最大功率耗散: 最大工作温度:+ 70 C 最小工作温度:- 40 C 安装风格:SMD/SMT 封装 / 箱体:QFN-20 封装:Reel |
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