LM136A National Semiconductor Corporation, LM136A Datasheet - Page 7

• Manufacturer Part Number: LM136A
• Description: Reference Diode
• Manufacturer: National Semiconductor Corporation

Temperature Drift
20139728
FIGURE 1. LM136 With Pot for Adjustment
of Breakdown Voltage
(Trim Range = ±120 mV typical)
20139727
Application Hints
The LM136 series voltage references are much easier to use
than ordinary zener diodes. Their low impedance and wide
operating current range simplify biasing in almost any circuit.
Further, either the breakdown voltage or the temperature co-
efficient can be adjusted to optimize circuit performance.
Figure 1 shows an LM136 with a 10k potentiometer for ad-
justing the reverse breakdown voltage. With the addition of
R1 the breakdown voltage can be adjusted without affecting
the temperature coefficient of the device. The adjustment
range is usually sufficient to adjust for both the initial device
tolerance and inaccuracies in buffer circuitry.
If minimum temperature coefficient is desired, two diodes can
be added in series with the adjustment potentiometer as
shown in Figure 2. When the device is adjusted to 2.490V the
temperature coefficient is minimized. Almost any silicon sig-
nal diode can be used for this purpose such as a 1N914,
20139729
1N4148 or a 1N457. For proper temperature compensation
FIGURE 2. Temperature Coefficient Adjustment
the diodes should be in the same thermal environment as the
(Trim Range = ±70 mV typical)
LM136. It is usually sufficient to mount the diodes near the
LM136 on the printed circuit board. The absolute resistance
of R1 is not critical and any value from 2k to 20k will work.
Low Cost 2 Amp Switching Regulator
†
20139705
*
L1 60 turns #16 wire on Arnold Core A-254168-2
≈
†
Efficiency
80%
7
www.national.com