- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄373936 > AD811 (Analog Devices, Inc.) High Performance Video Op Amp(高性能視頻運放) PDF資料下載
參數(shù)資料
| 型號： | AD811 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | High Performance Video Op Amp(高性能視頻運放) |
| 中文描述： | 高性能視頻運算放大器（高性能視頻運放） |
| 文件頁數(shù)： | 13/16頁 |
| 文件大?。?/td> | 286K |
| 代理商： | AD811 |
AD811
REV. C
–13–
A Video K eyer Circuit
By using two AD834 multipliers, an AD811, and a 1 V dc
source, a special form of a two-input VCA circuit called a
video keyer can be assembled. “K eying” is the term used in
reference to blending two or more video sources under the
control of a third signal or signals to create such special effects
as dissolves and overlays. T he circuit shown in Figure 41 is a
two-input keyer, with video inputs V
A
and V
B
, and a control
input V
G
. T he transfer function (with V
OUT
at the load) is
given by:
V
OUT
= G V
A
+ (1–G)
V
B
where G is a dimensionless variable (actually, just the gain of
the “A” signal path) that ranges from 0 when V
G
= 0, to 1
when V
G
= +1 V. T hus, V
OUT
varies continuously between V
A
and V
B
as G varies from 0 to 1.
Circuit operation is straightforward. Consider first the signal
path through U1, which handles video input V
A
. Its gain is
clearly zero when V
G
= 0 and the scaling we have chosen en-
sures that it is unity when V
G
= +1 V; this takes care of the
first term of the transfer function. On the other hand, the V
G
input to U2 is taken to the inverting input X 2 while X 1 is bi-
ased at an accurate +1 V. T hus, when V
G
= 0, the response to
video input V
B
is already at its full-scale value of unity,
whereas when V
G
= +1 V, the differential input X 1–X 2 is zero.
T his generates the second term.
T he bias currents required at the output of the multipliers are
provided by R8 and R9. A dc-level-shifting network comprising
R10/R12 and R11/R13 ensures that the input nodes of the
AD811 are positioned at a voltage within its common-mode
range. At high frequencies C1 and C2 bypass R10 and R11
respectively. R14 is included to lower the HF loop gain, and is
needed because the voltage-to-current conversion in the
AD834s, via the Y2 inputs, results in an effective value of the
feedback resistance of 250
; this is only about half the value
required for optimum flatness in the AD811’s response. (Note
that this resistance is unaffected by G: when G = 1, all the feed-
back is via U1, while when G = 0 it is all via U2). R14 reduces
the fractional amount of output current from the multipliers
into the current-summing inverting input of the AD811, by
sharing it with R8. T his resistor can be used to adjust the band-
width and damping factor to best suit the application.
T o generate the 1 V dc needed for the “1–G” term an AD589
reference supplies 1.225 V
±
25 mV to a voltage divider consist-
ing of resistors R2 through R4. Potentiometer R3 should be ad-
justed to provide exactly +1 V at the X 1 input.
In this case, we have shown an arrangement using dual supplies
of
±
5 V for both the AD834 and the AD811. Also, the overall
gain in this case is arranged to be unity at the load, when it is
driven from a reverse-terminated 75
line. T his means that the
“dual VCA” has to operate at a maximum gain of 2, rather
1
2
3
4
8
7
X1 +V
S
6
5
W1
X2
Y1
Y2
W2
–V
S
U1
AD834
7
6
4
3
2
U3
AD811
R8
29.4
R9
29.4
R12
6.98k
R13
6.98k
R10
C3
FB
V
OUT
FB
V
G
(0 TO +1V DC)
V
A
R6
226
R7
+5V
1
2
3
4
8
7
X1 +V
S
6
5
W1
X2
Y1
Y2
W2
–V
S
U1
AD834
–5V
+5V
U4
AD589
R5
113
(
±
1V FS)
–5V
R4
1.02k
R3
100
R2
174
R1
1.87k
V
B
(
±
1V FS)
+5V
–5V
C1
0.1μF
SER14
+5V
0.1μF
–5V
C4
0.1μF
C2
0.1μF
R11
LOAD
GND
LOAD
GND
Z
O
200
TO Y2
TO PIN 6
SETUP FOR DRIVING
REVERSE-TERMINATED LOAD
Z
O
200
V
OUT
INSET
Figure 41. A Practical Video Keyer Circuit
相關PDF資料 |
PDF描述 |
|---|---|
| AD8123 | Triple Differential Receiver with Adjustable Line Equalization |
| AD8123ACPZ-R2 | Triple Differential Receiver with Adjustable Line Equalization |
| AD8123ACPZ-R7 | Triple Differential Receiver with Adjustable Line Equalization |
| AD8123ACPZ-RL | Triple Differential Receiver with Adjustable Line Equalization |
| AD8129AR | Low-Cost 270 MHz Differential Receiver Amplifiers |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| AD811_04 | 制造商:AD 制造商全稱:Analog Devices 功能描述:High Performance Video Op Amp |
| AD8110 | 制造商:AD 制造商全稱:Analog Devices 功能描述:260 MHz, 16 x 8 Buffered Video Crosspoint Switches |
| AD8110AST | 制造商:Analog Devices 功能描述:Analog Video Crosspoint 390MHz 16 x 8 80-Pin LQFP 制造商:Rochester Electronics LLC 功能描述:TQFP 250MHZ 16X8 G=+1 BUF VID XPOINT SW. - Tape and Reel 制造商:Analog Devices 功能描述:SWITCH CROSSPOINT 16X8 SMD 8110 制造商:Analog Devices 功能描述:260 MHz, 168 Buffered Video Crosspoint Switches |
| AD8110ASTZ | 功能描述:IC VIDEO CROSSPOINT SWIT 80LQFP RoHS:是 類別:集成電路 (IC) >> 接口 - 模擬開關，多路復用器，多路分解器 系列:- 其它有關文件:STG4159 View All Specifications 標準包裝:5,000 系列:- 功能:開關 電路:1 x SPDT 導通狀態(tài)電阻:300 毫歐 電壓電源:雙電源 電壓 - 電源，單路/雙路(±):±1.65 V ~ 4.8 V 電流 - 電源:50nA 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:7-WFBGA，F(xiàn)CBGA 供應商設備封裝:7-覆晶 包裝:帶卷 (TR) |
| AD8110ASTZ | 制造商:Analog Devices 功能描述:Analog Crosspoint Switch IC |
發(fā)布緊急采購，3分鐘左右您將得到回復。