Question $3(25$ marks$)$

A circuit was built stage by stage as shown in Figure $3.$

The input source is a sinusoidal waveform with $230\frac{V_{ms}}{50}Hz.$

Figure $3$

a$)$ Explain briefly how the circuit in Stage $2$ works.

$(5$ marks $)$

b$)$ For each stage, sketch the output waveform $(V_0),$ and determine the respective peak and DC voltages.

$(20$ marks$)$