185MHz CRT Driver
CVA3424A / CVA3424
FEATURES
Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185MHz
Rise/Fall Time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5ns
Swing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40V
P-P
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80V
APPLICATIONS
CRT Driver for 2000 x 1600, 1600 x 1280 and 1280 x 1024
Monitors
DESCRIPTION
The CVA3424 Family is a video driver amplifier designed
specially to drive high resolution color monitors. With rise and
fall time of under 2.5ns and 185MHz bandwidth, this device
will provide excellent drive capability for the 2000 x 1600,
1600 x 1280 and 1280 x 1024 monitors.
ORDERING INFORMATION
Part
Package
Temperature
CVA3424AT
TO-220
-20
o
C to +90
o
C
CVA3424T
TO-220
-20
o
C to +90
o
C
CORPORATION
CONNECTION DIAGRAM AND SIMPLIFIED SCHEMATIC
11
10
9
8
7
6
5
4
3
2
1
PIN 1 DESIGNATOR
T11A
1C-04
GND
GND
NC
GND
in
V
out
V
cc
V
NC
NC
NC
NC
R
F
R
B
142
3.66k
V
CC
V
out
1B-04
CVA3424
V
in
9
11
GND
6,7,8
3
ABSOLUTE MAXIMUM RATINGS
Supply Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85V
Storage Temperature . . . . . . . . . . . . . . . . . . -25
o
C to +100
o
C
Operating Temperature . . . . . . . . . . . . . . . . . -20
o
C to +90
o
C
Lead Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . +300
o
C
CVA3424A / CVA3424
CORPORATION
FIGURE 1. TEST CIRCUIT
V
CC
L1
V
C C
V
in
INPUT
C2
R1
C3
R4
R5
R6
D1
D2
C4
C6
R1 = 270
R2 = 12k
(1 W)
R4 = 300k
R5 = 15
R6 = 15
C2 = Variable 4 to 150pF
Typical 27pF
C3 = 46pF
C4 = 10
f/160V
D1 = DS464
D2 = DS464
L1 = 150nH
OUTPUT
C
L
R2
C6 = 0.01
f/160V
C = 10pF (Including
Parasitics)
L
1B-05
CVA3424
V
out
3
9
6,7,8
GND
1
11
DC ELECTRICAL CHARACTERISTICS V
S
= 80V, C
L
= 10pF, V
out
= 40V
p-p
. See Figure 1. T
A
= +125
o
C unless otherwise noted.
SYMBOL
CHARACTERISTICS
MIN
TYP
MAX
UNITS
I
CC
Supply Current
45
55
mA
V
inDC
Iput DC Level
1.4
1.6
1.8
V
V
outDC
Output DC Level
34
40
46
V
A
V
Voltage Gain
11
13
15
V
Gain Matching
0.2
dB
AC ELECTRICAL CHARACTERISTICS V
S
= 80V, C
L
= 10pF, V
out =
40V
p-p
. See Figure 1. T
A
= +125
o
C unless otherwise noted.
SYMBOL
CHARACTERISTICS
CVA3424A
CVA3424
UNITS
MIN
TYP
MAX
MIN
TYP
MAX
t
r
Rise Time
2.2
2.9
2.5
3.5
ns
t
f
Fall Time
2.5
2.9
2.7
3.5
ns
BW
Bandwidth
185
150
MHz
Le
Linearity
5
5
%
OS / US
Overshoot / Undershoot
8
8
%
APPLICATIONS INFORMATION
Basic Circuit Configuration
The CVA3424 is a transimpedance amplifier with two stage
feedback amplifier configurations. Any change in input
current will be reflected as change in output voltage swing. A
resistor in series with the input will change the CVA3424 into
a voltage amplifier. The output is an emitter follower.
Because of the complementary circuitry employed, there is
no need for load or pull up resistor.
An internally bypassed capacitor is included inside the
package, however, for low frequencies an electrolytic
capacitor is recommended.
CVA3424 has an internal feedback resistor of 3.66K
. In the
absence of any input signal, the V
out
DC is set by
V
out
(
DC
)
=
(
1
+
R
F
R
B
)
V
in
(
DC
)
If an input signal is applied, the gain is set by
V
out
=
(
R
F
R
x
)
V
in
Input and Transfer Characteristics
An input current swing of
4.5mA causes the output to change
by
25V.
A resistor of 270
in series with the input will give a voltage
gain of -13.
Input pins are internal dc feedback nodes and thus have low
impedances. These pins must be fed from a series RC
network for high frequency emphasis.
Output Characteristics
The CVA3424 is intended to be used as the final stage of very
fast video circuits. The nominal load capacitance is 10pF. Other
values can be accommodated since the output stage is an
emitter follower and is fairly insensitive to load capacitance.
However, a wire connection of some length is unavoidable, that
causes objectionable ringing due to a resonant circuit. To avoid
this a damping resistor must be used in series with the lead
inductance. Also a resistor is necessary to protect the amplifier
against arching. A resistor of 30-50
will provide protection but
will slow down the response. The lead inductance may be
artificially increased by a tenth of a microHenry to obtain
desired peak. Any change in inductance will require
readjustment of damping resistor, as stated by equation (1).
R
=
L
C
(1)
The output of CVA3424 is not short circuit proof. Any
resistance to V+ or Ground should be >600
.
Thermal Characteristics
When low frequency square waves are amplified, some droop
will occur due to a large change in thermal dissipation in the
input transistors. To overcome this an R-C series feedback
network is suggested with 300k
and 46pF values. Under
normal operating conditions the CVA3424 will dissipate up to
6W. The maximum allowed case temperature is +90
o
C. To
calculate maximum heatsink thermal resistance use equation (2).
Rth
=
(
90
-
50
)
6W
=
6.7
C/W
CVA3424A / CVA3424
CORPORATION
FALL TIME
VOLTS
8V/DIV
2ns/DIV
BANDWIDTH
100
MHz
1
10
GA
IN
5dB
/
D
IV
0dB
RISE TIME
VOLTS
8V/DIV
2ns/DIV
CVA3424
CORPORATION
Information furnished by Calogic is believed to be accurate and reliable. However, no responsibility is assumed for its use: nor for any infringement of patents or other
rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent rights of Calogic.
CALOGIC CORPORATION
, 237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-1076
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