General-purpose NPN in the BC817 family
The Infineon BC817K16E6433HTMA1 is a 45 V, 500 mA NPN epitaxial silicon transistor in a SOT-23-3 surface-mount package. It belongs to the BC817 series, a widely used general-purpose switching and amplification transistor family. The '16' in the base number BC817-16 denotes the hFE grouping — this variant guarantees a DC current gain of 100 minimum at 100 mA collector current and 1 V VCE.
Switching performance at 170 MHz
With a transition frequency of 170 MHz, this transistor is fast enough for low-frequency switching regulators, relay and solenoid drivers, and signal amplification into the tens of megahertz. The 500 mW power dissipation limit in the SOT-23 package means you need to keep the junction temperature in check — the device is rated for a maximum junction temperature of 150 °C, so thermal design at continuous currents above 200 mA requires attention to PCB copper area.
Saturation voltage and drive requirements
The VCE(sat) is specified at 700 mV maximum with a base current of 50 mA driving 500 mA collector current. That's a forced beta of 10, typical for saturating a switching transistor. For lower collector currents the saturation voltage drops significantly. The 100 nA maximum collector cutoff current (ICBO) at 25 °C is tight enough for most general-purpose loads, though you'll want to add a base-emitter resistor if the circuit sees elevated temperatures or high-impedance base drive.
Last Buy — sourcing reality
Infineon has placed the BC817K16E6433HTMA1 into Last Buy status, meaning this specific order code is no longer in continuous production and has a final order window. If you have an active BOM line using this exact Infineon code, now is the time to secure lifetime buy quantities or qualify a drop-in replacement. The base product number BC817 is a standard industry type, and multiple manufacturers offer functionally equivalent NPN transistors in SOT-23 — but pin compatibility and hFE binning should be verified against your design's requirements.