LM134 Series Constant Current Source and Temperature Sensor UFEATURESDESCRIPTIO ■ 1µA to 10mA Operation The LM134 is a three-terminal current source designed to ■ 0.02%/V Regulation operate at current levels from 1µA to 10mA, as set by an ■ 0.8V to 40V Operating Voltage external resistor. The device operates as a true two- ■ Can be Used as Linear Temperature Sensor terminal current source, requiring no extra power connec- ■ Draws No Reverse Current tions or input signals. Regulation is typically 0.02%/V and ■ Supplied in Standard Transistor Packages terminal-to-terminal voltage can range from 800mV to 40V. UAPPLICATIO S Because the operating current is directly proportional to absolute temperature in degrees Kelvin, the device will ■ Current Mode Temperature Sensing also find wide applications as a temperature sensor. The ■ Constant Current Source for Shunt References temperature dependence of the operating current is ■ Cold Junction Compensation 0.336%/°C at room temperature. For example, a device ■ Constant-Gain Bias for Bipolar Differential Stage operating at 298µA will have a temperature coefficient of ■ Micropower Bias Networks 1µA/°C. The temperature dependence is extremely accu- ■ Buffer for Photoconductive Cell rate and repeatable. Devices specified as temperature ■ Current Limiter sensors in the 100µA to 1mA range are the LM134-3, LM234-3 and the LM134-6, LM234-6, with the dash numbers indicating ±3°C and ±6°C accuracies, respec- tively. If a zero temperature coefficient current source is re- quired, this is easily achieved by adding a diode and a , LTC and LT are registered trademarks of Linear Technology Corporation. resistor. UTYPICAL APPLICATIORemote Temperature Sensor with Voltage OutputOperating Current vs Temperature 500 225 VIN ≥ 5V 400 125 V+ °K) RSET = 226Ω TEMPERATURE ( R 300 25 RSET 10mV/°K –75 226Ω 200 LM234-3 V– °C) R1 TEMPERATURE ( 10k 100 –175 TA01a 0 –275 0 100 200 300 400 500 OPERATING CURRENT (µA) TA01b 1
