Page 1
ISO 9001 CERTIFIED BY DSCC
WIDE BANDWIDTH, VERY HIGH
VOLTAGE CRT VIDEO AMPLIFIER
641
M.S.KENNEDY CORP.
4707 Dey Road Liverpool, N.Y. 13088
FEATURES:
Pin Compatible with LH3424 and CR3424 High-Rel Versions
2nS Transition Times
Drives 8.5pF Capacitive Load With Ease
DC Coupled for Output Level Adjust
175MHz Bandwidth
75Vpp Output Swing
MIL-PRF-38534 CERTIFIED
(315) 701-6751
DESCRIPTION:
The MSK 641(B) is a wide bandwidth, high voltage color or monochrome CRT video amplifier designed specifically
to drive the cathode of today's most demanding high resolution CRT monitors. The MSK 641(B) is a transimpedance
amplifier capable of achieving a ±40V output voltage swing with an input current of ±10mA. The output of the
amplifier is DC biased at half the power supply voltage. Transition times in the range of 2nS enable the MSK 641 to
drive 10nS pixels with ease and make it ideally suited for monitors with 1280 x 1024 or higher display resolutions.
The 9 pin single in-line bathtub package is pin for pin compatible with the LH3424 and CR3424 and is a drop in
replacement for the high-rel versions of these devices with improved stability and thermal performance.
EQUIVALENT SCHEMATIC
TYPICAL APPLICATIONS
CRT Driver for Color and
Monochrome Monitors
High Voltage Transimpedance Amplifier
Ultra High Speed Amplifier for
Test Equipment
PIN-OUT INFORMATION
1
Inverting Input
2
Ground
3
Ground
4
Vcc
5
1
Vcc
6
7
8
9
Vcc
Ground
Ground
Output
Rev. B 8/00
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ABSOLUTE MAXIMUM RATINGS
+VCC
θJC
Supply Voltage
○○○○○○○○○○○○○○
Thermal Resistance
○○○○○○○○○
(Junction to Case)
IOUT
Peak Output Current
○○○○○○○○○○
ELECTRICAL SPECIFICATIONS
Parameter
STATIC
Power Supply Current
Input Bias Voltage
Output Offset Voltage
Input Capacitance
Power Supply Range
DYNAMIC CHARACTERISTICS
Output Voltage High
Output Voltage Low
Voltage Gain
Rise Time
Fall Time
Overshoot (Adjustable)
-3dB Bandwidth
Low Frequency Tilt Voltage
Linearity Error
2
2
2
2
+100V
10.5°C/W
250mA
Test Conditions
VIN=N/C
VIN=N/C
VIN=N/C
VIN=0.7V
Derated Performance
f=10KHz
f=10KHz
VIN=2VPP; f=10KHz
VOUT=40VPP
VOUT=40VPP
VOUT=20VPP
VOUT=20VPP
f=1KHz
f=10KHz; 5VPP≤VOUT≤50Vpp
1
TST
Storage Temperature Range
TLD
Lead Temperature Range
(10 Seconds)
TC
Case Operating Temperature
MSK641
MSK641B
TJ
Junction Temperature
○○○○○○○○○○○○
○○○○○○○○○○○
+Vcc=+80V Unless Otherwise Specified
Group A
Subgroup
1
2
3
1
2,3
1
2,3
-
-
4
4
4
4
4
-
-
-
4
Min.
-
-
-
1.4
1.35
38
46
-
60
75
-
10.5
-
-
-
130
-
-
MSK 641B
Typ.
40
55
35
1.55
-
40
40
10
80
78
2
12.5
2.1
2
25
175
-
0.5
-65°C to +150°C
○○○○○○○○○○
-40°C to +85°C
-55°C to +125°C
○○○○○○○○○○○
MSK 641
Min.
-
-
-
1.3
-
37
-
-
60
75
-
10
-
-
-
125
-
-
Typ.
40
55
35
1.55
40
10
80
78
12.5
2.1
25
175
0.5
Max.
45
65
45
1.7
1.8
42
44
-
100
-
5
14.5
2.9
2.9
-
-
-
5
300°C
175°C
50
1.8
43
5
15
3
3
5
Units
mA
mA
-
mA
-
V
-
V
V
-
-
V
pF
V
-
V
V
V/V
nS
nS
%
-
MHz
-
-
V
%
Max.
-
-
100
2
2
-
NOTES:
1
RIN=300Ω, CIN=100pF, CLOAD=8.5pF, RL=∞, unless otherwise specified (See Figure 1).
2
Guaranteed by design but not tested. Typical parameters are representative of actual device performance but are for reference only.
3
Industrial grade devices shall be tested to subgroups 1 and 4 unless otherwise specified.
4
Military grade devices ('B' suffix) shall be 100% tested to subgroups 1,2,3 and 4.
5
Subgroup 5 and 6 testing available upon request.
6
Subgroup 1,4 TA=TC=+25°C
Subgroup 2,5 TA=TC=+125°C
Subgroup 3,6 TA=TC=-55°C
Rev. B 8/002
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APPLICATION NOTES
TYPICAL TEST CIRCUIT
The signal source in Figure 1 can be either a fast pulse gen-
erator or a network analyzer as long as the output impedance is
50 ohms. The DC level of the input should be 1.55V and all
cables should be kept as short as possible. Since total load
capacitance should be kept below 8.5pF, a FET probe should
be used on the ouput.
USING THE MSK 641
The output of the amplifier is biased at one half of the power
supply voltage. An output voltage swing of ±35 volts is typi-
cal with a power supply voltage of +80 volts. With an 8.5pF
capacitive load, transistion times are in the 2.1nS range. If a
spark gap current limiting resistor is used on the output of the
amplifier and the transistion times are degraded, a peaking coil
may be used to preserve system performance. The optimum
value for this coil will be in the range of 100 to 200nH and can
best be determined by trial and error. The output of the MSK
641 is not short circuit protected, therefore, purely resistive
loads should be no less than 800 ohms at any time to avoid
damaging the output.
OPERATION CONSIDERATIONS
The input of the MSK 641 rests at a +1.55VDC level with
Vcc=+80VDC and the input terminal open. In this state, the
output rests at one half of the power supply voltage. When
connecting a pulse generator to the input of the amplifier, the
DC level should be offset so that the signal is centered around
+1.55V. During characterization, the input should be coupled
to the MSK 641 through a parallel combination of a variable
resistor and variable capacitor peaking circuit. Optimum values
for the peaking circuit can be determined experimentally. The
optimum value of load capacitance is 8.5pF. Viewing the out-
put with a normal oscilloscope probe would seriously degrade
performance. A FET probe fitted with a 100:1 voltage divider
will add only approximately 1.5pF of capacitance to the load
and is highly recommended. An experimental circuit along with
recommended values can be found in Figure 2.
OUTPUT ISSUES
The output of the MSK 641 is a pair of bipolar emitter follow-
ers configured in a complimentary push pull configuration. This
configuration eliminates the need for a pull up load resistor and
makes the amplifier less susceptible to load capacitance varia-
tions. Connecting a wire or cable from the output of the ampli-
fier to the CRT cathode can create a resonant circuit which can
cause unwanted oscillations or overshoot at its resonant fre-
quency. A damping resistor in series with the lead inductance
will alleviate this condition. The optimum value of this resistor
can be determined using the following formula:
R = 2* √L/C
This resistor also doubles as an arcing protector. In the bread-
boarding stage, the value of this resistor should be determined
experimentally. Resistance in the range of 50 to 100 ohms is
usually sufficient. If a quick, simple peaking network is de-
sired, a 300 ohm cable terminated by a capacitor will act like an
inductor in the frequency range involved.
TRANSIMPEDANCE AMPLIFICATION
Transimpedance amplifiers relate input current to output volt-
age. The MSK 641 contains an internal 4KΩ feedback resistor.
This resistor converts input current to output voltage in the
following manner (See Figure 1):
±1.43V (referenced to 1.55Vdc) across the 300Ω input re-
sistor results in an input current of ±4.77mA. This current
flows through the 4KΩ feedback resistor and results approxi-
mately in a ±20V swing at the output. The actual voltage gain
of the typical MSK641 circuit may be slightly less due to tran-
sistor losses. The following formula approximates voltage gain
including potential losses:
Voltage Gain (V/V) = 4KΩ/(Rin + L) L ≈ 25Ω
HEAT SINKING
The MSK 641 requires heat sinking in most applications. The
following formula may be applied to determine if a heat sink is
necessary and what size and type to use.
Rθsa = ((Tj-Ta)/Pd ) - (Rθjc) - (Rθcs)
WHERE
Tj = Junction Temperature
Pd = Total power dissipation
Rθjc = Junction to case thermal resistance
Rθcs = Case to heat sink thermal resistance
Rθsa = Heat sink to ambient thermal resistance
Tc = Case temperature
Ta = Ambient temperature
Ts = Sink temperature
EXAMPLE
Tj = 150°C
Ta = 100°C
Pd = 3W
Rθjc = 10.3°C/W
Rθcs = 0.15°C/W
Solving the above equation for Rθsa (heat sink thermal conduc-
tivity) shows that the heat sink for this application must have a
thermal resistance of no more than 6.2°C/W to maintain a junc-
tion temperature of no more than 150°C.
3
Rev. B 8/00
Page 4
TYPICAL PERFORMANCE CURVES
4
Rev. B 8/00
Page 5
COMPLETE VIDEO SYSTEM
Figure 3 above shows how an MSK 620 and MSK 641 can be used to drive a 100MHz monochrome monitor. The video signal
is A.C. coupled through C1. The video output pin of the MSK 620 rests at approximately +3.9Vdc and the input of the MSK 641
should be D.C. biased at approximately +1.55Vdc. D1, D2, D3 and Q1 act as a level shifting stage to match the output of the
MSK620 and the input of the MSK641. R8 and R9 sample the output and feed it back to the clamping section of the MSK 620 for
black level control superior to simply sampling from pin 14 of the MSK 620.
Rev. B 8/005
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MECHANICAL SPECIFICATIONS
NOTE: ESD Triangle indicates Pin 1.
ALL DIMENSIONS ARE ±0.010 INCHES UNLESS OTHERWISE LABELED
ORDERING INFORMATION
Number
MSK641
MSK641B
4707 Dey Road, Liverpool, New York 13088
Part
Screening Level
Industrial
Military-Mil-PRF-38534
M.S. Kennedy Corp.
Phone (315) 701-6751
FAX (315) 701-6752
www.mskennedy.com
The information contained herein is believed to be accurate at the time of printing. MSK reserves the right to make
changes to its products or specifications without notice, however, and assumes no liability for the use of its products.
Rev. B 8/006
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