As part of a radio transmitter design, a square wave oscillator has to drive a power mosfet. Given the gate capacitance and the frequency, the maximum current should be around 50mA.
The power mosfet is a little bit of an overkill (it works up to 2A), but RF mosfets don't go as high as I need, at least not the one I have. The oscillator can't source that much current, so I need a buffer that can source 50mA at 1MHz. The only buffers I know how to build are BJT followers with a common emitter, but they aren't fast enough. When switching it on and off, it takes time for it to go up to VCC again.