Gain increases as temperature increases. | Very high current gain which is nearly constant for varying drain currents. |

| Input Resistance | BJT's have Low Input resistance (often a bad thing) | MOSFET's have Very high input resistance. More than 107 Ohms (usually a good thing)

        For AC signals this figure can be much lower due to the capacitance of the device. |

| Thermal Runaway | When bipolar transistors heat up, the gain increases and so the current through them increases too. This in turn causes further heating and yet more gain and current. This can cause catastrophic failure called thermal runaway.

        Negative feedback helps to prevent this. | When MOSFETS heat up, the current flowing through them decreases. They are less likely to be destroyed by overheating |

| Bias (input) Voltages | Base current starts to flow with an input voltage of about +0.7V. Relatively large base currents are needed to make transistors operate. | N Channel MOSFETS need +2 to +4 volts to turn them on. The gate current is approximately zero. | | Saturation | The saturation voltage for BJT is given as  V_CE = 200 mV

        Low heat dissipation when saturated (fully turned on). | The saturation voltage for MOSFET is given as

V_DS = 20 mV Even lower heat dissipation when saturated (fully turned on). |