SNVS756C – APRIL 1998 – REVISED APRIL 2013
LM120/LM320-N Series 3-Terminal Negative Regulators
Check for Samples: LM120, LM320-N
•2 Preset Output Voltage Error Less than ±3%
• Preset Current Limit
• Internal Thermal Shutdown
• Operates with Input-Output Voltage Differential
down to 1V
• Excellent Ripple Rejection
• Low Temperature Drift
• Easily Adjustable to Higher Output Voltage
The LM120 series are three-terminal negative
regulators with a fixed output voltage of −5V, −12V,
and −15V, and up to 1.5A load current capability.
Where other voltages are required, the LM137 and
LM137HV series provide an output voltage range of
−1.2V to −47V.
The LM120 need only one external component—a
compensation capacitor at the output, making them
easy to apply. Worst case specifications on output
voltage deviation due to any combination of line, load
or temperature variation assure satisfactory system
Exceptional effort has been made to make the LM120
Series immune to overload conditions. The regulators
have current limiting which is independent of
temperature, combined with thermal overload
protection. Internal current limiting protects against
momentary faults while thermal shutdown prevents
junction temperatures from exceeding safe limits
during prolonged overloads.
Although primarily intended for fixed output voltage
applications, the LM120 Series may be programmed
for higher output voltages with a simple resistive
divider. The low quiescent drain current of the
devices allows this technique to be used with good
Table 1. LM120 Series Packages and Power
Figure 1. Dual Trimmed Supply
*Required if regulator is separated from
filter capacitor by more than 3 inches. For
value given, capacitor must be solid
tantalum. 25 μF aluminum electrolytic may
†Required for stability. For value given,
capacitor must be solid tantalum. 25 μF
aluminum electrolytic may be substituted.
Values given may be increased without
For output capacitance in excess of 100
μF, a high current diode from input to
output (1N4001, etc.) will protect the
regulator from momentary input shorts.
Figure 2. Fixed Regulator
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