What is thermal runaway in transistor?

Thermal runaway is a phenomenon that can occur in transistors when the temperature of the transistor increases due to excess heat generated by the device. This increase in temperature can cause the transistor to become even more conductive, which leads to an increase in current flow through the device. This in turn leads to an even greater increase in temperature, and so on, in a positive feedback loop. If left unchecked, this process can eventually cause the transistor to fail, either by damaging the device itself or by causing the surrounding circuit to malfunction.

Causes of thermal runaway

There are several factors that can contribute to thermal runaway in a transistor,

• High ambient temperatures.
• High levels of current flowing through the device.
• High levels of power dissipation.

Thermal runaway can occur in any type of transistor, including bipolar transistors (BJTs) and field-effect transistors (FETs). In a bipolar transistor, thermal runaway is typically caused by high levels of collector current and in a field-effect transistor, it is caused by high levels of drain current. In either case, the increase in temperature can cause the transistor to become more conductive, leading to an increase in current flow and an even greater increase in temperature.

Thermal runaway Prevention

• Using a heatsink or other cooling devices to dissipate excess heat.
• Using a transistor with a higher power rating to handle the required current and power levels.