This application note presents a method for the calculation of the MOSFET threshold voltage thermal coefficient (TVTC). TVTC is one of the main reasons for thermal runaway in linear operation of MOSFETs. The lower the TVTC, the higher the safe operating conditions of the MOSFET in linear operation.
The document discusses the operational conditions of MOSFET devices, specifically focusing on their use in linear zones within applications like audio amplifiers and air conditioning. It highlights that failure can occur due to thermal runaway when the threshold voltage thermal coefficient (TVTC) increases in absolute value. The note emphasizes the importance of selecting devices with low TVTC values for safe operation.
TVTC is achieved by deriving the MOSFET threshold voltage against temperature; it is a negative coefficient because the threshold voltage decreases as temperature increases.
A MOSFET works in a linear zone when it is subject to a high voltage or when a high current passes through the device.