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    •  BST 78, An Old N-MOSFET Tommie's blog

    I found BST 78s in an old drawer (salvaged from a school that has since been demolished.)

    Searching on the web gave pretty much web-bcs as the only information. It has a link to an image file of the datasheet.

    Here it is transcribed and translated from German, for anyone searching for the same thing:

    Silicon N-Channel Vertical D-MOS Field-Effect Transistor

    BST 78 Outline BST 78 Symbol

    Package: JEDEC TO-126

    The flange is electrically connected to Drain.

    Absolute Maximum Ratings

    Aspect Symbol Min Typ Max  
    Drain-Source Voltage UDS     450 V
    Drain-Source Voltage
    @ tP < 50 µs, non-periodic    		 UDS(P)     525 V
    Gate-Source Voltage
    @ ID = 0    		 UGS(0)     20 V
    Drain Current ID   0.75 1.5 A
    Power Dissipation PD     15 W
    Junction Temperature TJ     150 °C
    Storage Temperature TSTG -65   150 °C

    Characteristics

    Aspect Symbol Typ  
    On-Resistance
    @ UGS = 10 V, ID = 500 mA    		 RDS(on) 15 Ω
    Forward Transconductance
    @ UDS = 20 V, ID = 250 mA, f = 1kHz    		 g21s 400 mS
    Thermal Resistance, Junction-Package θJP 5 K/W
    Thermal Resistance, Junction-Ambient θJA 100 K/W