{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Chapter 5 Lecture - Part 4

Transient for p n junctions make the n region

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: cations • How to deal with this stored charge (and How transient voltage)? transient – For p+-n junctions, make the n-region shallower -n than Lp so that very little charge can be stored than – Add recombination center impurities (Au) into the Add n-region n-region Transient and AC Conditions Transient • Reserve Recovery Transient – In switching applications, the junction is switched In from forward bias to reverse bias modes frequently. – This affects the time-dependent charge – A reverse current that is much larger than the reverse normal reverse saturation current flows normal – Analysis is best performed using a p+-n junction -n with a square wave input with Storage delay time Storage in a p+-n diode in (a) circuit and input square wave; (b) hole distribution in the n-region as a function of time during the transient; (c) variation of current and voltage with time; (d) sketch of transient current and voltage on the device I–V characteristic. Transient and AC Conditions Transient • As the stored charge becomes depleted from the As junction, the following occurs: junction, – For Δpn positive, v(t) is positive and small, i ~ E/R until For Δpn goes to zero – When the charge is depleted and Δpn becomes negative, When v(t) becomes negative, • The source voltage, e(t), becomes divided between R and the The junction junction • Ir decreases as more of the source voltage appears across the reverse biased junction reverse – The time required for the stored charge (junction voltage) The to become zero is called the storage delay time (tsd) to Transients and AC Conditions Transients • Storage delay time: – – Its an error function Characteristic: It should be small relative to the Characteristic: switching time switching – How to decrease tsd • Shorten the lightly doped region • Introduce recombination centers (decrease carrier Introduce lifetimes) lifetimes) Effects of storage delay time on switching signal: (a) switching voltage; (b) diode current....
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online