LP395 Ultra Reliable Power Transistor
April 1998
LP395
Ultra Reliable Power Transistor
General Description
The LP395 is a fast monolithic transistor with complete over-
load protection. This very high gain transistor has included
on the chip, current limiting, power limiting, and thermal
overload protection, making it difficult to destroy from almost
any type of overload. Available in an epoxy TO-92 transistor
package this device is guaranteed to deliver 100 mA.
Thermal limiting at the chip level, a feature not available in
discrete designs, provides comprehensive protection against
overload. Excessive power dissipation or inadequate heat
sinking causes the thermal limiting circuitry to turn off the de-
vice preventing excessive die temperature.
The LP395 offers a significant increase in reliability while
simplifying protection circuitry. It is especially attractive as a
small incandescent lamp or solenoid driver because of its
low drive requirements and blowout-proof design.
The LP395 is easy to use and only a few precautions need
be observed. Excessive collector to emitter voltage can de-
stroy the LP395 as with any transistor. When the device is
used as an emitter follower with a low source impedance, it
is necessary to insert a 4.7 k鈩?resistor in series with the
base lead to prevent possible emitter follower oscillations.
Also since it has good high frequency response, supply
by-passing is recommended.
Areas where the LP395 differs from a standard NPN transis-
tor are in saturation voltage, leakage (quiescent) current and
in base current. Since the internal protection circuitry re-
quires voltage and current to function, the minimum voltage
across the device in the on condition (saturated) is typically
1.6 Volts, while in the off condition the quiescent (leakage)
current is typically 200 碌A(chǔ). Base current in this device flows
out of the base lead, rather than into the base as is the case
with conventional NPN transistors. Also the base can be
driven positive up to 36 Volts without damage, but will draw
current if driven negative more than 0.6 Volts. Additionally, if
the base lead is left open, the LP395 will turn on.
The LP395 is a low-power version of the 1-Amp LM195/
LM295/LM395 Ultra Reliable Power Transistor.
The LP395 is rated for operation over a 鈭?0藲C to +125藲C
range.
Features
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Internal thermal limiting
Internal current and power limiting
Guaranteed 100 mA output current
0.5 碌A(chǔ) typical base current
Directly interfaces with TTL or CMOS
+36 Volts on base causes no damage
2 碌s switching time
Connection Diagram
TO-92 Package
Typical Applications
Fully Protected Lamp Driver
DS005525-1
Order Number LP395Z
See NS Package Z03A
DS005525-3
漏 1999 National Semiconductor Corporation
DS005525
www.national.com
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