Generally, in digital circuits:

- Low impedance differential signals like those connecting ECL circuits.

- Switching the voltage of a large capacitance with high frequency, without regaining the stored energy. Example: Driving a MOSFET with an input capacitance of a few nF, using a push-pull stage, with a few 100 kHz or even some MHz.

In analog circuits:

- Class A amplifiers, due to the relatively high DC current even in the absence of a signal.

- Linear voltage regulators because power loss = (Vin - Vout) * Iout.