PNP power transistor — 45 V, 1.5 A in a through-hole TO-126
The BD136 is a PNP bipolar junction transistor rated for 45 V collector-emitter breakdown and 1.5 A continuous collector current, dissipating up to 1.25 W in the TO-225AA / TO-126-3 / SOT-32-3 through-hole package. It is a general-purpose device suited for medium-current switching and linear applications — motor drive, relay coil, solenoid, and audio output stages — where through-hole assembly is preferred or mandated. The 150°C junction temperature rating gives reasonable headroom for moderate heatsinking in free-air or forced-convection environments.
Vce(sat) is specified at 500 mV maximum with 50 mA base current driving 500 mA collector current — a typical switch-mode condition. The minimum DC current gain (hFE) is 40 at Vce = 2 V and Ic = 150 mA, which sets the base-drive requirement for a given load. For a 500 mA load, a base current of at least 12.5 mA ensures the transistor stays in saturation; the 500 mV drop at that point keeps conduction losses under 0.25 W. Off-state collector cutoff is 100 nA maximum (ICBO), clean enough for battery-powered circuits where leakage matters.
Package and mounting — through-hole only
The BD136 is supplied in a through-hole TO-225AA / TO-126-3 package, also designated SOT-32-3.