Re: HELP BJT transistor
What we often want from an amplifier is to have a voltage input and a voltage output. When you draw the small signal diagram of a BJT (or any transistor) you can see that, from a small-signal point of view, it's basically a voltage-to-current amplifier, or a transadmittance-amplifier. However, if we want to convert the resulting output current into an output voltage, the simplest thing we can do is to present an impedance to this current, and measure the resulting change in output voltage. In this case we created a voltage at the output, as we wanted. Hope this helped you!