A low side driver/switch is a connection that can “sink” a lot of current to ground (0V). It is called a low side drive (or switch) because the connection completes a path to the “low side”, otherwise known as the ground of a circuit.
A typical low-side drive is implemented by a NPN BJT (bi-polar junction transistor) or an N-MOSFET (N-channel metal oxide semiconductor field effect transistor).
Low-side drivers are useful to switch (turning on and off) most DC (direct current) devices. Many low-side drivers also have protection when the switched load is inductive. The protection usually consists of a fly-back diode on the load side, and optionally a TVS (transient voltage suppressor) on the switch side.
By selecting different N-MOSFETs or NPN BJTs, a low-side driver can sink current in the order of 100mAs all the way, with ease, to 10s of Amperes.
Applications: