Friday, May 27, 2011

PTC and NTC Thermistors - Murata

While PTC Ohms increments on Temperature rise, the NTC is the opposite its Ohmic Resistance drops with rise in temperature. Both types are very useful in Power Electronics and Electrical Immunity of Telecommunication Units.

NTC Thermistors - Murata

PTC and NTC Thermistors - Murata

Another application in in control systems, Temperature Measurement and Control. Watchdog Controllers to prevent a Burn-out of system, this happens when a software based electronic control system breaksdown or hangs.

Murata's PTC Thermistors called POSISTOR detect overheating to protect a circuit from drawing more than rated current in a equipment. This prevents a fire hazard and most important protects devices and units.

The NTC Thermistor are used in inrush current limiting and also temperature compensation in electronic products.

Protecting the MOSFET of DC-DC Converters from Overheating

Protecting the MOSFET of DC-DC Converters from Overheating

When the MOSFET temperature goes beyond the design limit the PTC thermistor which is thermally coupled to the device builds up its Ohmic Value, thereby the Emitter-Base Voltage rises to bias the NPN, which drinks away the bias meant for Mosfet. That works as the Foldback protection.

Thursday, May 26, 2011

Silicon PTC Thermistors - RTI Electronics

Extensively used in temperature compensating and sensing applications. Circuit design applications include power supplies and Over-Temperature protection.

Silicon PTC Thermistors - RTI Electronics

Positive Temperature Coefficient (PTC) thermistors - the resistance increments with temperature rise. An example application for 'Standard PTC Thermistors' of say 1 Ohm is Thermal runaway prevention in stacked power semiconductors. The Thermistor Thermally connected to the device/heatsink case, when device gets heated the current flow drops, as thermistor resistance increases, thereby balancing load. This Silicon PTC can also be used but in the bias or drive circuit as the resistance is more.

Silicon PTC Thermistors - RTI Electronics

Thermistors offer a regulation or monitor of temperature over a narrow range at a lower cost. Thermistors with minimum analog circuitry can replace bimetallic thermostats in most situations.

RTD and Thermocouples offer wider range and a more consistent output for Recording and Measurement. Thermistors are ideal for closed loop controls for protecting electrical equipment by limiting or cutting off the input power.

RTI Electronics designs, manufactures and sells thermistor, magnetic and film capacitor products. They also manufacture a full line of Magnetics, including Current Transformers & Sensors, Inductors & Power Transformers.

RTI Electronics, Inc. 1800 E. Via Burton St. Anaheim, CA 92806-1213

SM Series High-Value Resistors - Ohmcraft

SM Chip Resistors go to values in giga-ohms. The Technology - Micropenned serpentine patterned resistors, engineered for ultra precision.

SM Series High-Value Resistors - Ohmcraft
SM Series High-Value Resistors - Ohmcraft

These are surface mount resistors, the Resistive Element is Thick Film on Alumina Substrate. We can get Voltage Ratings upto 600 Volts and 50 Gigohms Values. Low noise high stability resistors.

Ohmcraft - Micropen Technologies Corporation
93 Paper Mill St., Honeoye Falls, NY 14472