LM334 - Adjustable Current Source
Direct substitute(s): LM134/LM234
by Tony van Roon, CET
The LM334 is 3-terminal adjustable current source featuring 10,000:1 range in operating current, excellent current
regulation and a wide dynamic voltage range of 1V to 40V. Current is established with one external resistor and no
other parts are required. Initial current accuracy is approximately 3%. The LM334 (same for LM134/LM234) are true
floating current sources with no separate power supply connections.
In addition, reverse applied voltages up to 20V will draw only a few dozen microamps of current, allowing the devices
to act as both rectifier and current source in AC applications. The LM334 was designed to operate at current levels
from 1µA to 10mA, as set by the external resistor. Since it operates as a true two-terminal current source, no
extra power, as mentioned before, and no input signals are required. Regulation is typically 0.02%/V and
terminal-to-terminal voltage can range from 800mV to 30V. Because the operating current is directly proportional to
absolute temperature in degrees Kelvin, this device will also find wide applications as a temperature sensor. The
temperature dependence of the operating current is +0.336%/°C at room temperature. For example, a device operating
at 298µA will have a temperature coefficient of +1µA/°C.
The temperature depence is extremely accurate and repeatable. If a zero temperature coefficient current source is
required, this is easily achieved by adding a diode and a resistor.
The LM334 is guaranteed over a temperature range of 0°C to +70°C. This device is available in TO-46 hermetic,
TO-92 (most common), and SO-8 plastic packages.
o Operates from 1V to 40V.
o 0.02%/V current regulation.
o Programmable from 1µA to 10µA.
o True 2-terminal operation.
o Available as fully specified temperature sensor.
o Approximately 3% initial accuracy.
o Fully 3-Terminal Adjustable Current Source.
o 3-pin or SO-8 surface mount package.
o V+ to V- Reverse voltage 20V.
o R Pin to V- Voltage 5V.
o Set current 10mA.
o Power dissipation 400mW.
o Soldering heat @ 260°C for 10 seconds maximum
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Copyright ©1998 - Tony van Roon