Question

1. what is the possible problem if b is equal to 15 v and c is equal to 15 v?

a. transistor is open
b. ( v _ { b b } ) is 0 v
c. transistor is shorted
d. ( v _ { c c } ) is 0 v

Explanation:

Step1: Analyze transistor operation

In a normal - operating transistor (assuming it's an NPN transistor here), when \(V_{BB}=15V\) and \(R_B = 470k\Omega\), the base current \(I_B=\frac{V_{BB}-V_{BE}}{R_B}\) (where \(V_{BE}\approx0.7V\) for a silicon transistor). The collector current \(I_C=\beta_{dc}I_B\). The voltage across \(R_C\) is \(V_{R_C}=I_CR_C\), and \(V_C = V_{CC}-V_{R_C}\). If \(V_C = V_{CC}=15V\), it means \(V_{R_C}=0V\), so \(I_C = 0A\).

Step2: Check transistor states

• If the transistor is open (infinite resistance between collector and emitter), there is no collector current \(I_C\). So \(V_C=V_{CC}\)
• If \(V_{BB} = 0V\), \(I_B=\frac{V_{BB}-V_{BE}}{R_B}\approx - \frac{0.7V}{470k\Omega}\approx0\), but \(V_B

eq15V\) as given.

• If the transistor is shorted (zero resistance between collector and emitter), \(V_C\approx V_E\approx0V\) (since emitter is grounded in this circuit)
• If \(V_{CC}=0V\), \(V_C\) cannot be \(15V\)

Answer:

A. transistor is open