LM195/LM395 Ultra Reliable Power Transistors
June 1999
LM195/LM395
Ultra Reliable Power Transistors
General Description
The LM195/LM395 are fast, monolithic power transistors
with complete overload protection. These devices, which act
as high gain power transistors, have included on the chip,
current limiting, power limiting, and thermal overload protec-
tion making them virtually impossible to destroy from any
type of overload. In the standard TO-3 transistor power pack-
age, the LM195 will deliver load currents in excess of 1.0A
and can switch 40V in 500 ns.
The inclusion of thermal limiting, a feature not easily avail-
able in discrete designs, provides virtually absolute protec-
tion against overload. Excessive power dissipation or inad-
equate heat sinking causes the thermal limiting circuitry to
turn off the device preventing excessive heating.
The LM195 offers a significant increase in reliability as well
as simplifying power circuitry. In some applications, where
protection is unusually difficult, such as switching regulators,
lamp or solenoid drivers where normal power dissipation is
low, the LM195 is especially advantageous.
The LM195 is easy to use and only a few precautions need
be observed. Excessive collector to emitter voltage can de-
stroy the LM195 as with any power transistor. When the de-
vice is used as an emitter follower with low source imped-
ance, it is necessary to insert a 5.0k resistor in series with
the base lead to prevent possible emitter follower oscilla-
tions. Although the device is usually stable as an emitter fol-
lower, the resistor eliminates the possibility of trouble without
degrading performance. Finally, since it has good high fre-
quency response, supply bypassing is recommended.
For low-power applications (under 100 mA), refer to the
LP395 Ultra Reliable Power Transistor.
The LM195/LM395 are available in standard TO-3 power
packages and solid Kovar TO-5. The LM195 is rated for op-
eration from 鈭?5藲C to +150藲C and the LM395 from 0藲C to
+125藲C.
Features
n
n
n
n
n
n
n
n
Internal thermal limiting
Greater than 1.0A output current
3.0 碌A typical base current
500 ns switching time
2.0V saturation
Base can be driven up to 40V without damage
Directly interfaces with CMOS or TTL
100% electrical burn-in
Simplified Circuit
DS006009-1
漏 1999 National Semiconductor Corporation
DS006009
www.national.com