I'm very familiar with the use of MOSFETs, I use BJTs on occasion, and I understand that the IGBT is just a combination of the two, but does anyone know when and why a particular device would or should be used?
For everything I do and can think of, I can use a MOSFET instead of a BJT or an IGBT with very few exceptions.
MOSFETs can switch faster and have a low on resistance (Rdson) so they make better switches than BJTs and IGBT which have a non-zero collector-emitter voltage (Vce). This also means that for high power they can typically consume less power. If I were driving 1A through a MOSFET with an Rdson of 250mOhms, it needs to dissipate 250mW. While a BJT/IGBT typically has a Vce of 0.5V and would dissipate 500mW. If the current requirement gets higher (say 10A), then that MOSFET definitely loses and dissipates more heat (25W vs 5W), however I can just choose a MOSFET with a lower Rdson (the smallest I've seen is 0.4mOhms) but I'd be hard pressed to find a Vce much lower with a different BJT/IGBT.
MOSFETs, BJTs, and IGBTs all can be setup in configurations that allow for amplification. MOSFETs can be a little trickier than BJTs and I assume IGBTs, but it is not impossible.
Controlling a MOSFET or IGBT is very power inexpensive as the control voltage uses almost no power, while a BJT constantly requires current for biasing, control, and amplifying. So in a power limited system a MOSFET/IGBT is the clear winner.
In low voltage systems, or voltage critical systems, you can deliver more voltage to the load with a MOSFET (again because of Vce). For instance if you have Blue LED (3.1V+) being powered in a system running at 3.3V, then a loss of 0.5V from the Vce of a BJT/IGBT is unacceptable, while the MOSFET will do it without any issues.
The MOSFET and I assume the IGBT however are susceptible to ESD on the gate, while the BJT is very robust. This is actually the main reason I still use BJTs.
The gate-source voltage (Vgs) is typically very low (20V typical, but I've seen as high as 30V) on MOSFETs (and I assume IGBTs), which is a disadvantage that a BJT does not suffer from. However, placing a voltage divider in front of the gate can resolve this issue most of the time.
MOSFETs allow current to pass both ways when on, and only one way (body diode) when off. This can be useful for some applications, but the body diode can be frustrating in others. The BJT (and I assume IGBT) are unidirectional and for the most part are fully off, when they are off. However the body diode is great for controlling something with inductance (motors, solenoids, relays, etc) as the back EMF generated when it is turned off can use it as a free wheeling diode, which reduces complexity and part count.
MOSFETs come in two main flavours (P-Type and N-Type). The N-Types are easy to control from low voltage sources as they are referenced to ground and can be used with a standard microprocessor pin connected to it without any issues; They are typically used on the low side of a load. P-types are referenced against the power source, which means you can't directly drive it from a microprocessor if the voltage source is higher than your micros. This can be resolved by using an additional N-type FET; but that adds cost and complexity. The P-types will typically control from the high side of the load.
So is there something I'm missing? Some limitations that I'm not aware of? Are some better at doing something than the others? Is it just that people are more familiar with the older technologies and not looking into other products? I'm genuinely curious and want it to be more nuanced then I have stated. I want to be a better designer, and I feel there must be something here that I'm missing.
For everything I do and can think of, I can use a MOSFET instead of a BJT or an IGBT with very few exceptions.
MOSFETs can switch faster and have a low on resistance (Rdson) so they make better switches than BJTs and IGBT which have a non-zero collector-emitter voltage (Vce). This also means that for high power they can typically consume less power. If I were driving 1A through a MOSFET with an Rdson of 250mOhms, it needs to dissipate 250mW. While a BJT/IGBT typically has a Vce of 0.5V and would dissipate 500mW. If the current requirement gets higher (say 10A), then that MOSFET definitely loses and dissipates more heat (25W vs 5W), however I can just choose a MOSFET with a lower Rdson (the smallest I've seen is 0.4mOhms) but I'd be hard pressed to find a Vce much lower with a different BJT/IGBT.
MOSFETs, BJTs, and IGBTs all can be setup in configurations that allow for amplification. MOSFETs can be a little trickier than BJTs and I assume IGBTs, but it is not impossible.
Controlling a MOSFET or IGBT is very power inexpensive as the control voltage uses almost no power, while a BJT constantly requires current for biasing, control, and amplifying. So in a power limited system a MOSFET/IGBT is the clear winner.
In low voltage systems, or voltage critical systems, you can deliver more voltage to the load with a MOSFET (again because of Vce). For instance if you have Blue LED (3.1V+) being powered in a system running at 3.3V, then a loss of 0.5V from the Vce of a BJT/IGBT is unacceptable, while the MOSFET will do it without any issues.
The MOSFET and I assume the IGBT however are susceptible to ESD on the gate, while the BJT is very robust. This is actually the main reason I still use BJTs.
The gate-source voltage (Vgs) is typically very low (20V typical, but I've seen as high as 30V) on MOSFETs (and I assume IGBTs), which is a disadvantage that a BJT does not suffer from. However, placing a voltage divider in front of the gate can resolve this issue most of the time.
MOSFETs allow current to pass both ways when on, and only one way (body diode) when off. This can be useful for some applications, but the body diode can be frustrating in others. The BJT (and I assume IGBT) are unidirectional and for the most part are fully off, when they are off. However the body diode is great for controlling something with inductance (motors, solenoids, relays, etc) as the back EMF generated when it is turned off can use it as a free wheeling diode, which reduces complexity and part count.
MOSFETs come in two main flavours (P-Type and N-Type). The N-Types are easy to control from low voltage sources as they are referenced to ground and can be used with a standard microprocessor pin connected to it without any issues; They are typically used on the low side of a load. P-types are referenced against the power source, which means you can't directly drive it from a microprocessor if the voltage source is higher than your micros. This can be resolved by using an additional N-type FET; but that adds cost and complexity. The P-types will typically control from the high side of the load.
So is there something I'm missing? Some limitations that I'm not aware of? Are some better at doing something than the others? Is it just that people are more familiar with the older technologies and not looking into other products? I'm genuinely curious and want it to be more nuanced then I have stated. I want to be a better designer, and I feel there must be something here that I'm missing.