Describe briefly, with the help of a diagram, an $n-p-n$ or $p-n-p$ transistor. Define current gain for a transistor.

Drawing a labelled circuit diagram, explain how a $p-n-p$ transistor can be used as an amplifier in common-emitter configuration? Derive expression for its voltage-gain.

Draw a labelled circuit diagram of common-emitter type transistor ($n-p-n$ or $p-n-p$) amplifier showing the biasing correctly.

Draw a labelled diagram of common emitter amplifier, showing waveforms of signal voltage and output voltage.

With proper labelling of the axes, draw the input and output characteristic curves of $n-p-n$ transistor in common-emitter configuration.

Draw a labelled circuit diagram of a simple common- emitter amplifier. What is the phase angle between the input and output voltages?

Figure below shows the circuit of an electronic device: Which electronic device : a rectifier, an amplifier or an oscillator does the circuit represent?