Explanation: Lateral pnp transistor has inferior characteristic as the base width is usually larger controlled by lateral diffusion of p-type impurities and photographic limitations during mask marking and alignment. Therefore, pnp transistor normally gives current gain as low as 1.5 to 30 compared to 50-300 for the npn transistor. 10. The diffusion of collector impurities in npn transistor should be small because,
A. No additional diffusion or masking steps required
B. Bandwidth is controlled by lateral diffusion of p-type impurity
C. Collector need not be kept at negative potential
D. None of the mentioned
Answer:A
Explanation: Lateral pnp transistor has inferior characteristic as the base width is usually larger controlled by lateral diffusion of p-type impurities and photographic limitations during mask marking and alignment. Therefore, pnp transistor normally gives current gain as low as 1.5 to 30 compared to 50-300 for the npn transistor. 10. The diffusion of collector impurities in npn transistor should be small because,
A. No additional diffusion or masking steps required B. Bandwidth is controlled by lateral diffusion of p-type impurity C. Collector need not be kept at negative potential D. None of the mentioned
Explanation: Generally, n-type impurities have smaller diffusion constant than p-type impurities, the n-type collector moves very little while p-type moves appreciably. Therefore, the diffusion coefficient of the collector impurities should be as small as possible to avoid the movement of the collector junction. 11. The advantage of Multi-emitter transistor is