A pn junction diode will be turned on when 1.5 V of an external voltage is appli

Question

A pn junction diode will be turned on when 1.5 V of an external voltage is applied to the nside of the diode while the p-side is grounded – T or F ?

(b) The net charge of a p-type silicon is zero – T or F ?

(c) Two ideal pn junction diodes are connected in parallel as shown in Figure 1. Assume that two diodes are identical. The current, i, should be positive and equally divided into each diode when vIN = 0.3 V and R = 1 k – T or F ?

(d) If two identical zener diodes (VZK = 5 V) are connected in series pointing each other, the voltage across the two zener diodes cannot exceed 5 V – T or F ?

(e) A zener diode and a pn junction diode work in the same fashion in forward-biased conditions – T or F ?

(f) If ambient temperature rises, the resistivity of an n-type silicon will decrease – T or F ?

Explanation / Answer

a. False

Reason:when 1.5 positive voltage is applied to n-side with p-side grounded , voltage across the pn diode will be -1.5v

the diode will be in reverse bias and it can not be turned on.

b.true

reason:

p and n type materials are NOT positively and negatively charged.

p-type material by itself has mainly positive charge carrier (holes) which are able to move relatively freely, but it is still neutral because the fixed acceptor atoms, having accepted electrons are negative.

c.figure is not given.more information is needed.

d.false

reason:when two zener diodes are connected in series pointing each other ,then one zener diode will be in reverse bias and other in forward bias .The voltage across reverse biased diode can be 5v and voltage across forward biased diode can be cutin voltage ,so the total voltage across two diodes can be more than 5v.

e.True

Reason:The zener diode and pn junction diode has almost same forward characteristics.Only the cutin voltage of zener diode is less than that of pn junction diode because zener diode is heavily doped compared to pn junction diode.

f.True

Reason:Semiconductors have negative temperature coefficient i.e., the resistivity decreases with increase in temperature.Semiconductors behave as insulator at 0K , as temperature increases it's conductivity increases because resistivity decreases.

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