4707 Dey Road Liverpool, N.Y. 13088
M.S.KENNEDY CORP.
(315) 701-6751
FEATURES:
Negative Output Voltage for Grid Drive
2.5nS Transition Times
Drives 8.5pF Capacitive Load With Ease
DC Coupled for Output Level Adjust
175MHz Bandwidth
50Vpp Output Swing
Replacement for CR2424R
WIDE BANDWIDTH, HIGH VOLTAGE
CRT VIDEO AMPLIFIER
EQUIVALENT SCHEMATIC
ISO 9001 CERTIFIED BY DSCC
642
DESCRIPTION:
The MSK 642(B) is a wide bandwidth, high voltage color or monochrome CRT video amplifier designed specifically
to drive the grid of today's most demanding high resolution CRT monitors. The MSK 642(B) is a transimpedance
amplifier capable of achieving a 25V output voltage swing with an input current of 9.3mA. The output of the
amplifier is DC biased at half the power supply voltage. Transition times in the range of 2.5nS enable the MSK 642
to drive 10nS pixels with ease and make it ideally suited for monitors with 1280 x 1024 or higher display resolutions.
The MSK 642 is mounted in a space efficient 9 pin single in-line bathtub package with heat sink fins.
CRT Driver for Color and
Monochrome Monitors
High Voltage Transimpedance Amplifier
Ultra High Speed Amplifier for
Test Equipment
TYPICAL APPLICATIONS
-Vee
Ground
Ground
Output
1
2
3
4
5
Inverting Input
Ground
Ground
-Vee
-Vee
6
7
8
9
PIN-OUT INFORMATION
MIL-PRF-38534 CERTIFIED
Rev. E 10/05
1
-65V
27C/W
250mA
1
2
3
4
5
6
7
Group A
Subgroup
1
2
3
1
2,3
1
2,3
-
-
4
4
4
4
4
-
-
-
4
V
IN
=N/C
V
IN
=N/C
V
IN
=N/C
V
IN
=0.7V
Derated Performance
f=10KHz
f=10KHz
V
IN
=2V
PP
; f=10KHz
V
OUT
=40V
PP
V
OUT
=40V
PP
V
OUT
=20V
PP
V
OUT
=20V
PP
f=1KHz
f=10KHz; 5V
PP
V
OUT
50V
pp
-65C to +150C
300C
-40C to +85C
-55C to +125C
175C
ABSOLUTE MAXIMUM RATINGS
T
ST
T
LD
T
C
T
J
Storage Temperature Range
Lead Temperature Range
(10 Seconds)
Case Operating Temperature
MSK642
MSK642B
Junction Temperature
Supply Voltage
Thermal Resistance
(Junction to Case)
Peak Output Current
-V
EE
JC
I
OUT
R
IN
=215
, C
IN
=100pF, C
LOAD
=8.5pF, R
L
=
, unless otherwise specified (See Figure 1).
Guaranteed by design but not tested. Typical parameters are representative of actual device performance but are for reference only.
Industrial grade devices shall be tested to subgroups 1 and 4 unless otherwise specified.
Military grade devices ('B' suffix) shall be 100% tested to subgroups 1,2,3 and 4.
Subgroup 5 and 6 testing available upon request.
Subgroup 1,4 T
A
=T
C
=+25C
Subgroup 2,5 T
A
=T
C
=+125C
Subgroup 3,6 T
A
=T
C
=-55C
Continuous operation at or above absolute maximum ratings may adversely effect the device performance and/or life cycle.
Typ.
-40
-55
-35
-1.55
-
-30
-
10
-60
-56
-4
12.5
2.5
2.5
25
175
-
0.5
Typ.
-40
-55
-35
-1.55
-
-30
-30
10
-60
-56
-4
12.5
2.5
2.5
25
175
-
0.5
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
Min.
-
-
-
-1.4
-1.35
-28
-26
-
-40
-54
-
10.5
-
-
-
125
-
-
Max.
-45
-65
-45
-1.7
-1.8
-32
-34
-
-65
-
-6
14.5
3.4
3.4
-
-
1.5
5
Min.
-
-
-
-1.3
-
-27
-
-
-40
-54
-
10
-
-
-
120
-
-
Max.
-50
-
-
-1.8
-
-33
-
-
-65
-
-6
15
3.5
3.5
-
-
1.5
5
MSK 642B
MSK 642
Parameter
Test Conditions
ELECTRICAL SPECIFICATIONS
-Vee=-60V Unless Otherwise Specified
2
2
2
2
1
mA
mA
mA
V
V
V
V
pF
V
V
V
V/V
nS
nS
%
MHz
V
%
Units
NOTES:
Rev. E 10/05
2
7
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 642
The output of the amplifier is biased at one half of the power
supply voltage. An output voltage swing of 25 volts is typi-
cal with a power supply voltage of -60 volts. With an 8.5pF
capacitive load, transistion times are in the 2.5nS 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
642 is not short circuit protected, therefore, purely resistive
loads should be no less than 600 ohms at any time to avoid
damaging the output.
OPERATION CONSIDERATIONS
The input of the MSK 642 rests at a -1.55VDC level with the
input terminal open. In this state, the output rests at one half
of the power supply voltage. When connecting a pulse genera-
tor to the input of the amplifier, the DC level should be offset
so that the signal is centered around -1.55V. During character-
ization, the input should be coupled to the MSK 642 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 capaci-
tance is 8.5pF. Viewing the output with a normal oscilloscope
probe would seriously degrade performance. A FET probe fit-
ted 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.
APPLICATION NOTES
OUTPUT ISSUES
The output of the MSK 642 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 grid 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.
HEAT SINKING
The MSK 642 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.
R
sa = ((Tj-Ta)/Pd ) - (R
jc) - (R
cs)
WHERE
Tj = Junction Temperature
Pd = Total power dissipation
R
jc = Junction to case thermal resistance
R
cs = Case to heat sink thermal resistance
R
sa = Heat sink to ambient thermal resistance
Tc = Case temperature
Ta = Ambient temperature
Ts = Sink temperature
EXAMPLE
Tj = 150C
Ta = 100C
Pd = 1.5W
R
jc = 27C/W
R
cs = 0.15C/W
Solving the above equation for R
sa (heat sink thermal conduc-
tivity) shows that the heat sink for this application must have a
thermal resistance of no more than 6.0C/W to maintain a junc-
tion temperature of no more than 150C.
TRANSIMPEDANCE AMPLIFICATION
Transimpedance amplifiers relate input current to output volt-
age. The MSK 642 contains an internal 3K
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 215
input
resistor results in an input current of 6.65mA. This current
flows through the 3K
feedback resistor and results approxi-
mately in a 20V swing at the output. The actual voltage gain
of the typical MSK 642 circuit may be slightly less due to tran-
sistor losses. The following formula approximates voltage gain
including potential losses:
Voltage Gain (V/V) = 3K
/(Rin + L) L
25
Rev. E 10/05
3
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