The LM134/LM234/LM334 are 3-terminal adjustable current sources 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 ±3%. The LM134/LM234/LM334 are true floating current sources with no separate power
supply connections. In addition, reverse applied voltages of up to 20V will draw only a few dozen
microamperes of current, allowing the devices to act as both a rectifier and current source in AC
applications.
The sense voltage used to establish operating current in the LM134 is 64mV at 25°C and is
directly proportional to absolute temperature (°K). The simplest one external resistor connection,
then, generates a current with ≈+0.33%/°C temperature dependence. Zero drift operation can be
obtained by adding one extra resistor and a diode.
Applications for the current sources include bias networks, surge protection, low power
reference, ramp generation, LED driver, and temperature sensing. The LM234-3 and LM234-6 are
specified as true temperature sensors with ensured initial accuracy of ±3°C and ±6°C, respectively.
These devices are ideal in remote sense applications because series resistance in long wire runs
does not affect accuracy. In addition, only 2 wires are required.
The LM134 is specified over a temperature range of −55°C to +125°C, the LM234 from −25°C
to +100°C and the LM334 from 0°C to +70°C. These devices are available in TO hermetic, TO-92 and
SOIC-8 plastic packages.
