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A power amplifier delivers 50 W output at 50% efficiency. The ambient temperature is 25° C. If the maximum allowable junction temperature is 150° C, then the maximum thermal resistance Qjc that can be tolerated is:
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- 25° C/W
- 20° C/W
- 5° C/W
- 1° C/W
Correct Option: C
PD = P0 × efficiency
= dissipated power at the output
| PD = | = 25 W | |
| 100 |
Given that, Ti = 150° C
TA = 25°C
Now,
| PD = | ||
| Qjc |
where, Ti = instantaneous temperature
TA = ambient temp.
| Qjc = | = | = 5° C/W | ||
| PD | 25 |
Qjc = thermal resistance
