PHYSICS 3K03 Quiz: 363DiodeFo
15 Sep 2017
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Diode approximations: (cid:1866),,(cid:1871) are constants, = 25mv usually. Usually, 1 is ignored avoid dealing with (cid:1871) (cid:1830) =(cid:1871) (cid:1857)(cid:1830)(cid:1866) 1 (cid:1830) =(cid:1871)(cid:1857)(cid:1830)(cid:1866) Most of the ti(cid:373)e it"s (cid:373)ore co(cid:374)ve(cid:374)ie(cid:374)t to use ratio of curre(cid:374)ts or voltage differe(cid:374)ces to. Small-signal diode model: (ac voltage with small amplitude) Usually more convenient to use ratio of currents or voltage difference. In this example, (cid:1871) (cid:1872) = 24 sin(cid:1872), 24 sin 2 = 12 i-v characteristics of real diodes shifts approximately -2 mv / (cid:1871) approximately doubles for every 10 increase (cid:1830) = ,(cid:1830) =(cid:1866) ln (cid:1830)(cid:1871) (cid:1870)(cid:1856) =(cid:1866)(cid:1830) Determine the dc biasing (q) operating point ((cid:1830),(cid:1830), the current and voltage of diode in dc- Determine small signal parameters (cid:1870)(cid:1856) or (cid:1859)(cid:1856) using (cid:1856: capacitors become open circuits. Draw small signal equivalent circuit: eliminate dc sources. Open-circuiting dc current source: capacitors become short circuited. Half-wave peak rectifiers (ideal diode) (cid:1870) (cid:1868)(cid:1829) = (cid:1868)(cid:1858)(cid:1829) Ideal diodes (cid:1870) - ripple voltage (cid:1868) - peak input voltage.
