ISO-9001 CERTIFIED BY DSCC
M.S.KENNEDY CORP.
4707 Dey Road Liverpool, N.Y. 13088
HIGH VOLTAGE
AMPLIFIER
690
(315) 701-6751
FEATURES:
Adjustable High Voltage Power Supply to +75V
Low Cost TO-3 Package
High Slew Rate - 2000V/µS Typical
Wide Bandwidth - 30MHz Typical
Low Transition Time - 20nS Typical at Full Swing
MIL-PRF-38534 CERTIFIED
DESCRIPTION:
The MSK 690 is a high voltage differential ampifier designed for use in CRT displays. With the high voltage power
supply set to +65 volts, the output voltage of the MSK 690 can swing from +5 volts to +60 volts at a rate of 2000
v/µS. The MSK 690 boasts a 30 MHz typical -3dB bandwidth and 20nS typical transition time making it a good
candidate for high speed systems. The circuit is packaged in a space efficient, hermetically sealed 8 pin TO-3 to
achieve good thermal efficiency and low cost. No isolation washer is necessary when heat sinking this device. The
MSK 690 is available in both industrial and military grades.
EQUIVALENT SCHEMATIC
TYPICAL APPLICATIONS
High Voltage Op-Amp
CRT Display Driver
High Voltage ATE Pin Driver
Level Shifter
1
2
3
4
PIN-OUT INFORMATION
Inverting Input
-V
CC
Ground
Output
1
8
7
6
5
Non-Inverting Input
Ground
+V
HV
Case Connection
Rev. A 8/00
APPLICATION NOTES
ADJUSTABLE HIGH VOLTAGE POWER SUPPLY CASE CONNECTION
The high voltage power supply of the MSK 690 can be ad-
justed from +40 volts to +75 volts. To minimize device power
dissipation, the +V
HV
power supply should be decreased as
much as possible without causing output signal clipping. The
following formula can be used to select a value for +V
HV
:
+V
HV
= V
OUTMAX
+ 5.0V
This will ensure that the transistion times are not degraded due
to the output transistor temporarily going into saturation.
The case of the MSK 690 is internally connected to pin five
of the package. This pin can be left as a no connect but it is
recommended that the user connect this pin to ground to re-
duce noise and improve overall circuit stability.
DECOUPLING AND LAYOUT
Since the MSK 690 is a high voltage amplifier, it is com-
monly used in high gain configurations. Consequently, any
noise introduced into the system through the power supplies
will be amplified by the system gain. It is therefore imperative
that proper power supply decoupling and printed circuit card
layout guidelines are adhered to. Each power supply should be
effectively decoupled with a parallel combination of capacitors
as shown in the Typical Inverting Connection Diagram. These
capacitors should be connected as close as possible to the pack-
age pins and lead lengths must be kept to a minimum. On the
printed circuit card, the input and output traces should be kept
apart whenever possible to avoid localized feedback. The power
supply lines should be kept as wide as possible to keep their
effective impedance down thereby minimizing pickup.
FEEDBACK CAPACITANCE
The gain range of the MSK 690 is ±5V/V to ±100V/V. When
configured for low closed loop gains in the range of ±5V/V to
±25V/V, a small 0.5pF to 2.0pF adjustable capacitor should
be placed in parallel with the feedback resistor. This capacitor
can be adjusted to tailor overshoot and minimize ringing de-
pending on the load. For closed loop gains greater than ±25V/
V the user may omit this capacitor without any loss in circuit
stability. See the table below labeled "recommended compo-
nent values" and the typical connection diagram for compo-
nent selection vs. closed loop gain.
RECOMMENDED COMPONENT VALUES
A
V
-5V/V
-10V/V
-50V/V
-100V/V
-R
IN
510Ω
270Ω
500Ω
500Ω
R
f
2.7KΩ
2.7KΩ
25KΩ
50KΩ
+R
IN
499Ω
249Ω
495Ω
499Ω
Cf
0.5-2.0pF
0.5-2.0pF
N/A
N/A
SOURCE RESISTOR SELECTION
When driving reactive loads, such as the effective capaci-
tance of a cathode ray tube, local oscillations may often occur
in the output transistors of the op-amp. To minimize these
oscillations, an output source resistor may be added in series
with the amplifier output and the capacitive load as seen in the
figure below. This R-C combination acts as a snubber network
that lowers the high frequency bandwidth. The source resistor
is typically in the 10 ohm to 100 ohm range. In exchange for
increased overall circuit stability, a minor reduction in amplifier
bandwidth may occur. The following formula may be used to
approximate the frequency at which the zero will occur on the
open loop plot due to the addition of the isolation resistor.
f
ZERO
= 1/(2π(R
ISO
+ R
O
) C
LOAD)
TYPICAL INVERTING CONNECTION DIAGRAM
3
SOURCE RESISTOR CONNECTION
Rev. A 8/00
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