In: Electrical Engineering
Why has the MOSFET outperformed the bipolar transistor?
Both MOSFET and BJT are used in switching converters. In older days, bipolar transistors were mostly used. However, now a days, MOSFET is used widely. There are certain advantages of MOSFET that helped it gaining an upper edge over BJT. The advantages are as follows.
1. MOSFET is voltage controlled device but BJT is current controlled device. Hence MOSFETs are used in many digital circuits because voltage signals can easily operate them, unlike BJTs.
2. The power handling capacity of MOSFET is more than that of a BJT.
3. Due to lesser switching losses, MOSFETs can operate in higher frequencies unlike BJTs. As a result, most high frequency switching converters prefer MOSFET over BJT.
4. The scalability of MOSFET gives it a significant advantage compared to BJT. MOSFETs can be scaled down to a smaller size maintaining the same current passing through it while for a BJT, size matters for a particular current to pass through it. In short, MOSFETs are easy to fabricate.
5. BJTs suffer from the problem of thermal runway but this phenomenon is missing in case of MOSFETs.
6. MOSFET has higher input impedance than BJT
Due to the above mentioned reasons, MOSFET has outperformed the bipolar transistor.