Mitsubishi DPLUS 74SB -BKA Service Manual page 149

Typical Performance Characteristics
(VCC = +80V), Test Circuit – Figure 3 unless other-
wise specified.
THEORY OF OPERATION
The circuit diagram of the LM2480 is shown in Figure
1. The DC clamp circuit amplifies the input signal by
–18 and the gain is set by the resistor ratio of 18R
and R. The output requires pull-up resistor to 80V.
Figure 2 shows the test circuit used for evaluation of
the LM2480 Clamp Amplifier. A high impedance
voltmeter (100MW) is used for DC measurements at
the output. The DC transfer function is shown in Figure
4.
APPLICATION HINTS
Power Supply Bypass
The LM2480 should have proper power supply
bypassing for optimum performance. A 0.1mF capacitor
should be connected from the supply pin, V
as close to the supply and ground pins as is practical.
Additionally, a 1.0mF electrolytic capacitor should be
connected from the supply pin to ground. The
electrolytic capacitor should also be placed reasonably
close to the LM2480's supply and ground pins.
Application Circuit
The application circuit shown in Figure 5 is designed
to help clamp the voltage at the output of the driver to
the desired level. Capacitor C
node at the anode of the clamp diode, D
a low impedance at high frequencies. Figure 5 also
shows the standard application circuit topology when
used with an LM246X CRT driver. It shows all the
components necessary to optimize performance as
well as to protect against damage from a CRT arc event.
No additional components are required to protect the
LM2480 from arc damage.
Demonstration Hardware
National Semiconductor has designed a demonstra-
to ground,
tion neckboard for the LM126X, LM246X, and the
CC
LM2480 chipset. To obtain demonstration board con-
tact the National Semiconductor Sales Office in your
region.
7-48
stabilizes the entire
4
, by creating
3