LM3911N

The LM3911 is a highly accurate temperature measurement and/or control system for use over a —25°C to + 85°C tem-perature range. Fabricated on a single monolithic chip, it includes a temperature sensor, a stable voltage reference and an operational amplifier. The output voltage of the LM3911 is directly proportional to temperature in degrees Kelvin at 10 mV/°K. Using the inter-nal op amp with external resistors any temperature scale factor is easily obtained. By connecting the op amp as a comparator, the output will switch as the temperature trans-verses the set-point making the device useful as an on-off temperature controller. An active shunt regulator is connected across the power leads of the LM3911 to provide a stable 6.8V voltage refer-ence for the sensing system. This allows the use of any power supply voltage with suitable external resistors. The input bias current is low and relatively constant with temperature, ensuring high accuracy when high source im-pedance is used. Further, the output collector can be re-turned to a voltage higher than 6.8V allowing the LM3911 to drive lamps and relays up to a 35V supply. The LM3911 uses the difference in emitter-base voltage of transistors operating at different current densities as the ba-sic temperature sensitive element. Since this output de-pends only on transistor matching the same reliability and stability as present op amps can be expected. The LM3911 is available in two package styles, a metal can TO-46 and an 8-lead epoxy mini-DIP. In the epoxy package all electrical connections are made on one side of the de-vice allowing the other 4 leads to be used for attaching the LM3911 to the temperature souce. The LM3911 is rated for operation over a —25°C to + 85°C temperature range.