LM193J/883 National Semiconductor, LM193J/883 Datasheet - Page 5

• Manufacturer Part Number: LM193J/883
• Description: IC,VOLT COMPARATOR,DUAL,BIPOLAR,DIP,8PIN,CERAMIC
• Manufacturer: National Semiconductor

Applications
for current sharing. When Q1 turns “on” all bases are pulled
up to V
since the input PNP’s are reverse biased.
A two terminal current/power limiter is shown in Figure 6.
The base and collector are shorted — turning the power
transistor on. If the load current exceeds 2 amps, the device
current limits protecting the load. If the overload remains on,
the device will thermal limit, further protecting itself and the
load. In normal operation, only 2V appear across the device
so high efficiency is realized and no heat sink is needed.
Another method of protection would be to place the mono-
lithic power transistor on a common heat sink with the de-
vices to be protected. Overheating will then cause the
LM195 to thermal limit protecting the rest of the circuitry.
The low base current make this power device suitable for
many unique applications. Figure 7 shows a time delay
circuit. Upon application of power or S1 closing, the load is
energized. Capacitor C1 slowly charges toward V
R1. When the voltage across R1 decreases below about 0.8
volts the load is de-energized. Long delays can be obtained
with small capacitor values since a high resistance can be
used.
+
FIGURE 6. Two Terminal Current Limiter
and no base current flows in the LM195 transistors
FIGURE 7. Time Delay Circuit
(Continued)
00741806
00741807
−
through
5
†
Figure 8 and Figure 9 show how the LM195 can be used with
standard IC’s to make positive or negative voltage regula-
tors. Since the current gain of the LM195 is so high, both
regulators have better than 2 mV load regulation. They are
both fully overload protected and will operate with only 2V
input-to-output voltage differential.
An optically isolated power transistor is shown in Figure 10.
D1 and D2 are almost any standard optical isolator. With no
drive, R1 absorbs the base current of Q1 holding it off. When
Solid tantalum.
FIGURE 8. 1 Amp Positive Voltage Regulator
FIGURE 9. 1 Amp Negative Regulator
www.national.com
00741808
00741809