9.3. Numerical Problem and Analysis

Try these first

1. 1.

   What are the primary currents in a transistor?

   Hint

   Think of the current flowing into and out of the transistor.

2. 2.

   Explain the meaning of forward biasing in a transistor.

   Hint

   Look at the roles of voltages at different junctions.

3. 3.

   What is the necessary condition for an n-p-n transistor to operate in an active region?

   • Base-Emitter Junction Reverse Biased
   • Base-Collector Junction Forward Biased
   • Base-Emitter Junction Forward Biased

   Hint

   Consider how the voltage needs to be arranged for current to flow.

4. 4.

   True or False: The collector current is always greater than the base current in an active transistor.

   • True
   • False

   Hint

   Think about the role of beta in the transistor operation.

5. 5.

   Analyze a two-stage amplifier using n-p-n transistors. If the first stage has a β of 200 and a base current of 5 mA, determine the output current produced by the second stage boosting this output by an additional factor.

   Hint

   Consider how current flows through each stage based on the relationships we have discussed.

6. 6.

   Design a bias network for a p-n-p transistor to achieve I_E of 15mA at V_EB = 0.7V. What supply voltage is needed if the load resistance is 1kΩ?

   Hint

   Remember to account for the voltage drop across the base-emitter junction when calculating the supply voltage needed.