LM2480
Typical Performance Characteristics
(V
CC
= +80V), Test Circuit - Figure 3 unless otherwise specified.
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
4
stabilizes the entire node at the anode of
the clamp diode, D
3
, by creating 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 perfor-
mance as well as to protect against damage from a CRT arc
event. No additional components are required to protect the
LM2480 from arc damage.
20008304
FIGURE 4. V
out
vs V
in
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 (
>
100MΩ) is used for DC mea-
surements at the output. The DC transfer function is shown
in Figure 4.
APPLICATION HINTS
20008307
Power Supply Bypass
The LM2480 should have proper power supply bypassing for
optimum performance. A 0.1µF capacitor should be con-
nected from the supply pin, V
cc
, to ground, as close to the
supply and ground pins as is practical. Additionally, a 1.0µF
electrolycelectrolytictic capacitor should be connected from
FIGURE 5. One Channel of the LM2480 and LM246X
Application Circuit
Demonstration Hardware
National Semiconductor has designed a demonstration
neckboard for the LM126X, LM246X, and the LM2480
chipset. To obtain demonstration boards contact the National
Semiconductor Sales Office in your region.
3
www.national.com
NSC [ NATIONAL SEMICONDUCTOR ]
