參數(shù)資料
型號(hào)： VCA822IDGS
廠商： Texas Instruments, Inc.
英文描述： Wideband, > 40dB Gain Adjust Range, Linear in V/V VARIABLE GAIN AMPLIFIER
中文描述： 寬帶，“40dB的增益調(diào)整范圍在V，線性音頻/視頻可變?cè)鲆娣糯笃?/td>
文件頁(yè)數(shù)： 20/35頁(yè)
文件大?。?/td> 837K
代理商： VCA822IDGS
www.ti.com
FOUR-QUADRANT MULTIPLIER
A four-quadrant multiplier can easily be implemented
using the VCA822. By placing a resistor between FB
and V
IN
, the transfer function depends upon both V
IN
and V
G
, as shown in
Equation 1
.
DIFFERENCE AMPLIFIER
Because
both
high-impedance,
implemented
implementation is shown in
Figure 80
. This circuit
provides
excellent
common-mode
(CMRR) as long as the input is within the CMRR
range of –2.1V to +1.6V. Note that this circuit does
not make use of the gain control pin, V
G
. Also, it is
recommended to choose R
S
such that the pole
formed by R
S
and the parasitic input capacitance
does not limit the bandwidth of the circuit. The
common-mode
rejection
implemented in a gain of +10V/V for V
G
= +1V is
shown in
Figure 81
. Note that because the gain
control voltage is fixed and is normally set to +1V, the
feedback element can be reduced in order to
increase the bandwidth. When reducing the feedback
element make sure that the VCA822 is not limited by
common-mode input voltage, the current flowing
through R
G
, or any other limitation described in this
data sheet.
V
=
OUT
′
V
V
+
G
′
IN
R
F
R
G
R
F
R
G
-
R
F
R
1
′
V
IN
(1)
V
=
OUT
′
V
V
IN
′
G
R
F
R
G
(2)
R
F
+V
IN
R
G+
R
G
-
-
V
IN
FB
R
G
R
2
R
3
20
W
V
IN
V
G
R
S
Source
Impedance
R
1
VCA822
R
F
+V
IN
R
G+
R
G
-
-
V
IN
FB
R
G
R
S
R
S
20
W
V
IN+
V
IN
-
VCA822
95
90
40
Frequency (Hz)
C
100k
100M
85
45
75
80
10M
1M
50
55
60
65
70
Input-Referred
1.5
1.0
-
1.5
Time ( s)
A
0
1
10
2
0.5
-
1.0
-
0.5
0
9
8
7
6
5
4
3
V
OUT
V
IN
V
G
f
= 1MHz
f
= 0.1MHz
IN
VG
VCA822
SBOS343A–SEPTEMBER 2007–REVISED OCTOBER 2007
inputs
a
of
the
amplifier
major
VCA822
are
be
This
difference
any
can
without
problem.
rejection
ratio
Setting R
1
to equal R
G
, the term that depends only on
V
IN
drops out of the equation, leaving only the term
that depends on both V
G
and V
IN
. V
OUT
then follows
Equation 2
.
ratio
for
this
circuit
Figure 78. Four-Quadrant Multiplier Circuit
The behavior of this circuit is illustrated in
Figure 79
.
Keeping the input amplitude of a 1MHz signal
constant and varying the V
G
voltage (100kHz, 2V
PP
)
gives
the
modulated
output
Figure 79
.
Figure 80. Difference Amplifier
voltage
shown
in
Figure 81. Common-Mode Rejection Ratio
Figure 79. Modulated Output Signal of the
4-Quadrant Multiplexer Circuit
20
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Copyright 2007, Texas Instruments Incorporated
Product Folder Link(s):
VCA822
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VCA822IDGSR 功能描述:運(yùn)算放大器 - 運(yùn)放 WB >40dB Gain Adj Rng Lin V/V Var Gain RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
VCA822IDGSRG4 功能描述:運(yùn)算放大器 - 運(yùn)放 WB >40dB Gain Adj Rng Lin V/V Var Gain RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
VCA822IDGST 功能描述:運(yùn)算放大器 - 運(yùn)放 WB >40dB Gain Adj Rng Lin V/V Var Gain RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
VCA822IDGSTG4 功能描述:運(yùn)算放大器 - 運(yùn)放 WB >40dB Gain Adj Rng Lin V/V Var Gain RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
VCA822IDR 功能描述:運(yùn)算放大器 - 運(yùn)放 WB >40dB Gain Adj Rng Lin V/V Var Gain RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
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