This post explains for the transistor 2SA1972.
The Part Number is A1972.
The function of this semiconductor is PNP Transistor.
Manufacturers : Toshiba Semiconductor
Preview images :
This is Silicon PNP Triple Diffused Type Transistor.
TOSHIBA 2SA1972 High-Voltage Switching Applications Unit: mm • High breakdown voltage: VCEO = −400 V Absolute Maximum Ratings (Ta = 25°C) Characteristics Collector-base voltage Collector-emitter voltage Emitter-base voltage Collector current Base current Collector power dissipation Junction temperature Storage temperature range DC Pulse Symbol VCBO VCEO VEBO IC ICP IB PC Tj Tstg Rating −400 −400 −7 −0.5 −1 −0.25 900 150 −55 to 150 Unit V V V A A mW °C °C JEDEC TO-92MOD JEITA ― Note1: Using continuously under heavy loads (e.g. the application of high temperature/current/voltage and the significant change in TOSHIBA 2-5J1A temperature, etc.) may cause this product to decrease in the Weight: 0.36 g (typ.) reliability significantly even if the operating conditions (i.e. operating temperature / current / voltage, etc.) are within the absolute maximum ratings. […]
Absolute maximum ratings ( Ta=25°C )
1. Collector to Base Voltage : Vcbo = – 400 V
2. Collector to Emitter Voltage : Vceo = – 400 V
3. Emitter to Base Voltage : Vebo = – 7 V
4. Collector Current : Ic = – 0.5 A
5. Collector Dissipation : Pc = 900 mW
6. Junction Temperature : Tj = 150°C
7. Storage Temperatue : Tsg = -55 ~ +150°C