Topic: Electronic Devices
For the 2N338 transistor, the manufacturer specifies $P_{max}=100~mW$ at $25^{\circ}C$ free air temperature and the maximum junction temperature $T_{j~max}=125^{\circ}C$. Its thermal resistance is
- A. $10^{\circ}C/W$
- B. $100^{\circ}C/W$
- C. $1000^{\circ}C/W$
- D. $10,000^{\circ}C/W$
Answer: C. $1000^{\circ}C/W$
Explanation: $(T_{j}-T_{A})=\theta P_{c,max} \Rightarrow (125-25)=\theta\times100~mW \Rightarrow \theta=1000^{\circ}C/W$.