Discussion

Match List I with List II and select the correct answer using codes given below :

List I	List II
(a) Gunn diode	(i) exhibit stray capacitances and inductances at higher frequencies
(b) GaAs FET	(ii) has small capacitance when reverse biased
(c) Conventional transistor	(iii) transferred electron device
(d) Pin diode	(iv) used in low noise amplifier

Answer: A

The correct matching is a-iii, b-iv, c-i, d-ii.

A Gunn diode works by the transferred electron effect in GaAs, where electrons move into a higher, low-mobility valley (iii).
A GaAs FET (MESFET) is the classic low noise microwave amplifier device (iv).
A conventional transistor suffers from stray capacitances and lead inductances at high frequencies, which limit its microwave use (i).
A PIN diode has a very small capacitance when reverse biased, because the wide intrinsic layer separates the charges, which suits it to microwave switching (ii).

The codes that swap the last two items give the PIN diode the parasitic problem that it is designed to avoid.

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