50 V / 500 mA PNP — the gain and the saturation floor
The 50A02CH-TL-E is a PNP general-purpose transistor from onsemi, rated for 50 V collector-emitter breakdown and 500 mA continuous collector current. The headline DC current gain is 200 minimum at 10 mA, 2 Vce — so at moderate drive currents the base current needed is under 50 µA, easy for a logic output or a microcontroller GPIO to source. The saturation voltage is 120 mV max at 10 mA base, 100 mA collector — that low Vce(sat) keeps conduction loss negligible in a saturated switch.
690 MHz transition frequency — what it buys you
The 690 MHz fT means the transistor still has useful gain well into the VHF band. For switching applications, that translates to clean edges at hundreds of kilohertz — think a 100 kHz PWM dimmer or a 1 MHz DC-DC converter feedback path. The 3-CPH package (SOT-23-3) keeps parasitic inductance low enough that the fT is usable, not just a datasheet number. At 150°C maximum junction temperature, the part lives in warm environments — a power supply brick or a motor drive enclosure — without derating the power dissipation below 700 mW, provided the board copper carries the heat. The 100 nA collector cutoff at 25°C is tight; at 85°C expect it to climb but stay under a few microamps, fine for most switched loads.