Basic Questions (usually asked in phone interview) (© Fuding Ge)

1. Tell me a little bit about semiconductors (what is conductance and valence band? Fermi level? For n type semiconductor, what is the doping? Do you know how to say P and As in English?)

2. How does a pn junction works? (I know you know it, but could you tell other people clearly? Try it!!!, They ask you this question!). What is the depletion region? What is the build-in potential? What is the relation between these parameters with doping concentration and temperature? Remember the tempo of the build-in potential is about ?mV/K.

3. Tell me how MOSFET works. (Write it down in your own words and remember it !!!).

4. Tell me how BJT works. (Should I write down and remember it? Sure! But it is less asked). How does Vbe and Ic change with temperature?

5. Threshold voltage: If the substrate doping concentration increase, or temperature increases, how will Vt change? it increase or decrease?

6. Tell me what is Channel length modulation, what is Early effects and their physical origin.

7. Tell me what is short Channel effect.

8. For a 0.18um and 0.8um technology MOSFET, which has a higher cutoff frequency?

9. How does a Bandgap Voltage reference work?

10. What is the ideal input and output resistance of a current source? How about voltage source? How to improve these parameters? (Cascode topology, use long channel transistors)

11. Tell me the parameters as many as possible you know that used to character an amplifier.

12. What are the two types of noise of MOSFET, how to eliminate them? (Thermal and Flicker).

Basic Questions (usually asked in phone interview) (© Fuding Ge)