鈥?/div>
HIGH VOLTAGE INSTRUMENTATION
PIEZO TRANSDUCER EXCITATION
PROGRAMMABLE POWER SUPPLIES UP TO 430V
ELECTROSTATIC TRANSDUCERS & DEFLECTION
PATENTED
TYPICAL APPLICATION
Dynamic focusing is the active correction of focusing volt-
age as a beam traverses the face of a CRT. This is necessary
in high resolution flat face monitors since the distance be-
tween cathode and screen varies as the beam moves from the
center of the screen to the edges. PA85 lends itself well to this
function since it can be connected as a summing amplifier with
inputs from the nominal focus potential and the dynamic
correction. The nominal might be derived from a potentiom-
eter, or perhaps automatic focusing circuitry might be used to
generate this potential. The dynamic correction is generated
from the sweep voltages by calculating the distance of the
beam from the center of the display.
DC
FOCUS
X SWEEP
SAMPLE
z = x
2
+ y
2
Y SWEEP
SAMPLE
R
IN2
PA85
TO
FOCUS
GRID
R
IN1
R
F
+225V
DESCRIPTION
The PA85 is a high voltage, high power bandwidth MOSFET
operational amplifier designed for output currents up to 200mA.
Output voltages can swing up to
鹵215V
with a dual supply and
up to +440 volts with a single supply. The safe operating area
(SOA) has no second breakdown limitations and can be
observed with all types of loads by choosing an appropriate
current limiting resistor. High accuracy is achieved with a
cascode input circuit configuration. All internal biasing is
referenced to a bootstrapped zener-MOSFET current source.
As a result, the PA85 features an unprecedented supply range
and excellent supply rejection. The MOSFET output stage is
biased on for linear operation. External compensation pro-
vides user flexibility.
This hybrid circuit utilizes thick film (cermet) resistors, ce-
ramic capacitors and silicon semiconductor chips to maximize
reliability, minimize size and give top performance. Ultrasoni-
cally bonded aluminum wires provide reliable interconnec-
tions at all operating temperatures. The 8-pin TO-3 package is
hermetically sealed and electrically isolated. The use of com-
pressible isolation washers voids the warranty.
R
CL
鈥?25V
EQUIVALENT SCHEMATIC
D1
Q1
Q2
Q4
D23
COMP
7
8
Q12
Q6
鈥揑N
5
Q10A
Q10B
Q17
Q18
Q13
Q16
D2
鈥揤
S
6
Q7
+IN
4
Q11
1
OUT
Q9
C
L
2
3
+V
S
EXTERNAL CONNECTIONS
+Vs
CL
R
CL
Q8
3
2
1
OUT
+IN
4
TOP VIEW
鈥揑N
PHASE COMPENSATION
R
C
Gain
C
C
1
68pF
100鈩?/div>
20
10pF
330鈩?/div>
100
3.3pF
0鈩?/div>
C
C
RATED FOR FULL
SUPPLY VOLTAGE
5
6
鈥揤s
8
7
COMP
COMP
C
C
R
C
APEX MICROTECHNOLOGY CORPORATION
鈥?TELEPHONE (520) 690-8600 鈥?FAX (520) 888-3329 鈥?ORDERS (520) 690-8601 鈥?EMAIL prodlit@apexmicrotech.com
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