Switch from 5v to 24v - 150kHz - 20mA
Drive a small MOSFET such as 2N7000 or 2N7002 with your 5V signal. In the below schematic, the 200\$\Omega\$ resistor represents the source impedance of your 5V signal- it doesn't have to be an actual resistor. 







simulate this circuit &ndash; Schematic created using CircuitLab



The MOSFET (assuming it's a small one like I suggest) is easier to drive and suffers less from storage effects than a BJT. If you really want to use a BJT you can connect a BAT54 Schottky diode from collector to base to act as a Baker Clamp to avoid saturation, or drive the transistor with a resistor in the emitter as a constant(-ish) current sink.