Q.Which type of negative feedback decreases both input and output impedances of an amplifier?

In an amplifier either the output voltage or the output current can be sampled, and the feedback signal can be returned either in series or in parallel (shunt) with the input. Combining these two choices gives four basic types of negative feedback. In each name the first word tells what is sampled at the output and the second tells how the feedback is connected at the input:

1. Voltage series (shunt-derived, series-fed): output voltage sampled, fed in series with the input; $\beta = V_f/V_o$.
2. Voltage shunt (shunt-derived, shunt-fed): output voltage sampled, fed in parallel at the input; $\beta = I_f/V_o$.
3. Current series (series-derived, series-fed): output current sampled, feedback voltage fed in series; $\beta = I_f/I_o$.
4. Current shunt (series-derived, shunt-fed): output current sampled, fed in parallel; $\beta = V_f/I_o$. …