a change in I c . We define a parameter ac , which is similar to the dc defined in Eq. ( . ), as c c ac B b I i I i ' ( .
) which is also known as the ac current gain A i . Usually ac is close to dc in the linear region of the output characteristics. The change in I c due to a change in I B causes a change in V CE and the voltage drop across the resistor R L because V CC is fixed. FIGURE .
A simple circuit of a CE-transistor amplifier.