Analysis V D = E V R = 0 V I D = 0 A

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1 Electronic Circuits Load-Line Line Analysis Prof. Nizamettin AYDN The load line plots all possible combinations of diode current ( D ) and voltage ( D ) for a given circuit. The maximum D equals E/, and the maximum D equals E. The point where the load line and the characteristic curve intersect is the Q-point, which identifies D and D for a particular diode in a given circuit. 1 2 Series Diode Configurations Series Diode Configurations Forward Bias Constants Silicon Diode: D = 0.7 Germanium Diode: D = 0.3 Analysis (for silicon) D = 0.7 (or D = E if E < 0.7 ) = E D D = = T = / everse Bias Diodes ideally behave as open circuits Analysis D = E = 0 D = 0 A 3 4 Parallel Configurations Half-Wave ectification D = = = 0.7 D1 D2 O = 0.7 = 9.3 E D 10.7 = = = 28 ma.33kω 28 ma = = = 14 ma D1 D2 2 The diode only conducts when it is forward biased, therefore only half of the AC cycle passes through the diode to the output. The DC output voltage is m, where m = the peak AC voltage

2 P (P) Full-Wave ectification Because the diode is only forward biased for one-half of the AC cycle, it is also reverse biased for one-half cycle. t is important that the reverse breakdown voltage rating of the diode be high enough to withstand the peak, reverse-biasing AC voltage. P (or P) > m P = Peak inverse voltage P = Peak reverse voltage m = Peak AC voltage The rectification process can be improved by using a full-wave rectifier circuit. Full-wave rectification produces a greater DC output: Half-wave: dc = m Full-wave: dc = m 7 8 Full-Wave ectification Full-Wave ectification Bridge ectifier Four diodes are connected in a bridge configuration DC = m Center-Tapped Transformer ectifier equires Two diodes Center-tapped transformer DC = m 9 10 Summary of ectifier Circuits Diode Clippers ectifier Half Wave ectifier Bridge ectifier Center-Tapped Transformer ectifier deal DC DC = m DC = m DC = m ealistic DC DC = m 0.7 DC = m 2(0.7 ) DC = m 0.7 The diode in a series clipper clips any voltage that does not forward bias it: A reverse-biasing polarity A forward-biasing polarity less than 0.7 (for a silicon diode) m = peak of the AC voltage. n the center tapped transformer rectifier circuit, the peak AC voltage is the transformer secondary voltage to the tap

3 Biased Clippers Parallel Clippers Adding a DC source in series with the clipping diode changes the effective forward bias of the diode. The diode in a parallel clipper circuit clips any voltage that forward bias it. DC biasing can be added in series with the diode to change the clipping level Summary of Clipper Circuits Summary of Clipper Circuits more Clampers Biased Clamper Circuits A diode and capacitor can be combined to clamp an AC signal to a specific DC level. The input signal can be any type of waveform such as sine, square, and triangle waves. The DC source lets you adjust the DC clamping level

4 Summary of Clamper Circuits Zener Diodes The Zener is a diode operated in reverse bias at the Zener oltage ( z ). When i Z The Zener is on oltage across the Zener is Z Zener current: Z = L The Zener Power: P Z = Z Z When i < Z The Zener is off The Zener acts as an open circuit Zener esistor alues oltage-multiplier Circuits f is too large, the Zener diode cannot conduct because the available amount of current is less than the minimum current rating, ZK. The minimum current is given by: Lmin = The maximum value of resistance is: Lmax = ZK Z Lmin oltage multiplier circuits use a combination of diodes and capacitors to step up the output voltage of rectifier circuits. oltage Doubler oltage Tripler oltage Quadrupler f is too small, the Zener current exceeds the maximum current rating, ZM. The maximum current for the circuit is given by: L Z Lmax = = L Lmin The minimum value of resistance is: Lmin Z = i Z oltage Doubler oltage Doubler Positive Half-Cycle o D 1 conducts o D 2 is switched off o Capacitor C 1 charges to m This half-wave voltage doubler s output can be calculated by: out = C2 = 2 m Negative Half-Cycle o D 1 is switched off o D 2 conducts o Capacitor C 2 charges to m out = C2 = 2 m where m = peak secondary voltage of the transformer

5 oltage Tripler and Quadrupler Practical Applications ectifier Circuits Conversions of AC to DC for DC operated circuits Battery Charging Circuits Simple Diode Circuits Protective Circuits against Overcurrent Polarity eversal Currents caused by an inductive kick in a relay circuit Zener Circuits Overvoltage Protection Setting eference oltages