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Tel: +81 (03) 3349-5501
Fax: +81 (03) 3349-5505
ABSOLUTE MAXIMUM RATINGS
PARAMETER
Supply Voltage V
S
Operating Temperature Range
Storage Temperature Range
Lead Temperature (Soldering, 10 Sec)
Differential Video Input Voltage
Clamp Input Voltage
VALUE
±13.5 V
0°C
≤
T
A
≤
70° C
-65°C
≤
T
S
≤
150° C
260° C
±5 V
CAUTION
ELECTROSTATIC
SENSITIVE DEVICES
DO NOT OPEN PACKAGES OR HANDLE
EXCEPT AT A STATIC-FREE WORKSTATION
V
EE
+ 2.5 V
≤
V
CL
≤
V
cc
- 2.5 V
ELECTRICAL CHARACTERISTICS
PARAMETER
Supply Voltage
POWER
SUPPLIES
+ Supply Current
- Supply Current
SIGNAL
PATH
Maximum Input Voltage
Above V
CL
Insertion Loss
Full Power Bandwidth
GB4550
SIGNAL
PATH
Small Signal Bandwidth
Frequency Response
Signal Path Delay
Delay Tolerance
Full Power Bandwidth
Small Signal Bandwidth
GB4550A
SIGNAL
PATH
Frequency Response
Signal Path Delay
Delay Tolerance
Differential Gain
SIGNAL
PATH
Differential Phase
Input Resistance
Input Capacitance
Output Resistance
Clamp Voltage Range
CLAMP
Clamp Accuracy
VS = ±10 V, T
A
= 0 - 70°C, R
L
= 10kΩ, C
L
= 150 pF, CCOMP = 0 pF unless otherwise shown.
SYMBOL
V
S
I+
I-
V
IN MAX
I.L.
FPBW
SSBW
CONDITIONS
Operating Range
MIN
±9
-
-
1.8
TYP
±10
9
9
2.0
-
18
25
0.05
-8
±1.5
20
30
0.1
-7.5
±0.15
0.02
0.03
100
2.0
8.6
53
-
7
MAX
±12
13.8
13.8
2.25
0.03
-
-
-
-
-
-
-
-
-
-
0.05
0.05
-
-
-
-
+5.5
28
UNITS
V
mA
mA
V
dB
MHz
MHz
dB
deg
deg
MHz
MHz
dB
deg
deg
%
deg
kΩ
pF
Ω
Ω
V
mV
ƒ = 100kHz
-3.0dB, V
IN
= 1V p-p
±0.2dB, V
IN
= 100mV p-p
at 10MHz, V
IN
= 1V p-p
-
15
20
-
-
-
17
25
-
-
-
-
-
80
-
ø
D
FPBW
SSBW
at 3.58MHz
at 3.58MHz
-3.0dB, V
IN
= 1V p-p
±0,1dB, V
IN
=100mV p-p, C
L
=100pF
at 10MHz, V
IN
= 1V p-p
ø
D
dg
dp
R
IN
C
IN
R
OUT
V
CL
at 3.58 MHz
at 3.58MHz
at 3.58MHz
at 3.58MHz
A
V
= +1, ƒ = 0 to 10MHz
A
V
= +1, ƒ = 100MHz
-
-
-5.5
V
IN
= 1V p-p
-
520 - 34 - 5
2 of 5
DETAILED DESCRIPTION
The GB4550(A) is intended for video applications requiring
coarse DC restoration coupled with flat frequency response.
As shown in Figure 1, the signal path features a wide band
operational amplifier designed to be unity gain stable. While
this amplifer is not intended to drive 75
Ω
transmission lines,
it is ideal for applications where high capactive loads, up to
several hundred picofarads, must be driven, such as input
buffering and DC restoration of video signals.
Optimal frequency response for the GB4550(A) occurs with
load capacitances in the range of 80 pF to 100 pF as shown
in Figure 4. For smaller loads, an external capacitor can be
added to extend the bandwidth and improve the flatness of
the device response.
The clamping function is achieved through the use of a simple
comparator. The inverting input of the comparator is connected
to the GB4550(A) output, while the non-inverting input is
connected to the clamp voltage reference. For output signal
voltages more positive than the clamp reference the comparator
output is essentially open-circuit, while signal voltages more
negative than the clamp reference result in the charging of C
X
.
The action of the comparator is to provide a positive current
which is fed back to the op-amp non-inverting input under
conditions where the op-amp output is more negative than the
clamp reference voltage. This negative feedback raises the
DC level of the input signal to the point where all signal
fluctuations occur at voltages above the clamp reference
level. This is the desired clamp action.
The input to the op-amp must be AC coupled using an
appropriate size of capacitor, which then acts as a DC
"reservoir" for the corrective level shift.
Under equilibrium conditions the average current supplied by
the comparator output is just sufficient to balance the current
discharging the input capacitor. This discharge current is
simply the input bias current of the op-amp, typically less than
20 µA . However, an external resistor can be added to increase
the pull down current. Under dynamic conditions, where the
system is adjusting for a change in the signal level, the
charging current may be in the milliamp range. Because the
corrective current is small under equilibrium conditions, the
error voltage at the comparator input is small also, so clamping
accuracy to within ±7 mV is achievable.
The clamp circuit makes use of a "peak hold" capacitor, C
X
, at
the output of the comparator . This gives rise to a more
constant voltage at the comparator output which is translated
to a more constant corrective current by an internal 100 kΩ
resistor connected between the comparator output and the
signal input.
To avoid excessive phase shift and consequent instability of
the clamp feedback loop, the peak hold capacitor needs to be
considerably smaller (e.g. 1000 times) than the input coupling
capacitor. If a faster clamp is desirable (e.g. for 60 Hz hum
elimination) the peak hold capacitor can be removed and a
smaller input coupling capacitor employed. In this application
some distortion of the signal "tip" is unavoidable.
C
X
(+2 V OUTPUT CLAMP)
100k
(NC on
GB4550A)
30k
+
10pF
V
CL
COMP
-
+IN
+
-
30k
-IN
V
CC
7mA
Nominal
V
EE
All resistors in ohms, all capacitors in microfarads unless otherwise stated.
OUT
Fig. 1 Simplfied Circuit Diagram
3 of 5
520 - 34 - 5
+10V
0.1
-10V
0.1
+5V
0.1
4
SIGNAL IN
FROM
NETWORK
ANALYSER
*22
1
NON-POLAR
2
6
1
0.1
D.U.T.
8
7
3
10k
**R
COMP
-5V
4
CLC110
5
8
OUTPUT TO
NETWORK
ANALYSER
5
75
10n
All resistors in ohms,
all capacitors in microfarads
unless otherwise stated.
**C
COMP
C
LOAD
0.1
NOTES:
This circuit can be used for Frequency Response, Delay and Differential Gain and Phase measurements.
* This input capacitor must be shorted out when performing Differential Gain and Phase tests.
** RCOMP and CCOMP are only used on GB4550.
Fig. 2 Test Circuit
+10V
0.1
-10V
0.1
GX4314
XPOINT
VIDEO OUT 1
4 2
0.1 to 22
1
NON-POLAR
6
GX4314
XPOINT
8
7
GX4314
XPOINT
VIDEO OUT 2
VIDEO
IN
GB4550
GB4550A
5
3
*R
COMP
VIDEO OUT 3
All resistors in ohms,
all capacitors in microfarads
unless otherwise stated.
**
10n
*C
COMP
C
LOAD
GX4314
XPOINT
VIDEO OUT 4
NOTES:
In most applications R
COMP
and C
COMP
will not be needed since the bandwidth depends on the bus capacitance.
In general, the maximum occurs when C
LOAD
is between 82 pF and 100 pF.
They are used to control the roll-off for higher load conditions.
*
Not used on GB4550A.
**
The value of this capacitor should be proportional to the input capacitor used.
The value shown is for a 22 µF input capacitor.
Fig. 3 Typical Application Circuit
520 - 34 - 5
4 of 5
Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement.
便携式数字数据采集系统（PDDAS）使用了LabVIEW实时模块和PXI，以控制风洞测试和采集记录来自128个不同通道的空气压力数据 "通过LabVIEW实时模块，可以在各种操作情况下获得采集空气压力数据及向风洞提供反馈控制信号所需的确定性响应时间。" – Dave Scheibenhoffer, G Systems 挑战: 用一个可采集、分析和存储来自下一代喷气式战斗机引擎设计的动...[详细]
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