Chapter 2 Diode Applications LoadLine The applied load

Load-Line The applied load to the circuit will normally have an important impact on

Load-Line Analysis The load line (the applied load) plots all possible combinations of diode

Series Diode Configurations Forward Bias Constants • Silicon Diode: VD = 0. 7 V

Series Diode Configurations Reverse Bias Diodes ideally behave as open circuits Analysis • VD

EXAMPLE For the series diode determine (a) VDQ and IDQ. (b) VR. Electronic Devices

Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright ©

EXAMPLE For the series diode configuration, determine VD, VR, and ID. Electronic Devices and

• Since the applied voltage establishes a current in the clockwise direction to

EXAMPLE • Determine Vo and ID for the series circuit Electronic Devices and Circuit

Parallel Configurations Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky

Example Determine the current I for the network: Electronic Devices and Circuit Theory, 10/e

Example: Determine the voltage Vo for the network Electronic Devices and Circuit Theory, 10/e

Half-Wave Rectification The diode only conducts when it is forward biased, therefore only half

PIV (PRV) Because the diode is only forward biased for one-half of the AC

Full-Wave Rectification The rectification process can be improved by using a full-wave rectifier circuit.

Full-Wave Rectification Bridge Rectifier • • Four diodes are connected in a bridge configuration

Full-Wave Rectification Center-Tapped Transformer Rectifier Requires • Two diodes • Center-tapped transformer VDC =

Summary of Rectifier Circuits Rectifier Ideal VDC Half Wave Rectifier VDC = 0. 318

EXAMPLE Determine the output waveform for the following network and calculate the output dc

For the positive region of the input voltage Electronic Devices and Circuit Theory, 10/e

For the negative part of the input the roles of the diodes will be

AND/OR GATES Positive logic OR gate. Electronic Devices and Circuit Theory, 10/e Robert L.

AND/OR GATES positive logic AND gate Electronic Devices and Circuit Theory, 10/e Robert L.

PIV For The Bridge Configuration The required PIV of each diode at the peak

PIV For Center-tapped Transformer Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and

Diode Clippers Clipper is a variety of diode networks that have the ability to

Series Clippers • The diode in a series clipper “clips” any voltage that does

Biased Clippers Adding a DC source in series with the clipping diode changes the

Example Determine the output waveform for the network Electronic Devices and Circuit Theory, 10/e

The network will appear as below, and vo=vi +5 V. Electronic Devices and Circuit

Parallel Clippers The diode (ideal) in a parallel clipper circuit “clips” any voltage that

Example Determine vo for the following network Electronic Devices and Circuit Theory, 10/e Robert

Summary of Clipper Circuits more… Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad

Summary of Clipper Circuits Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and

Clampers A diode and capacitor can be combined to “clamp” an AC signal to

Biased Clamper Circuits The input signal can be any type of waveform such as

In general, the following steps may be helpful when analyzing clamping networks: 1. Start

Example Determine vo for the following network for the input indicated. Electronic Devices and

• The analysis will begin with the period t 1 → t 2

• The open-circuit equivalent for the diode will remove the 5 -V battery

Summary of Clamper Circuits Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and

Zener Diodes The Zener is a diode operated in reverse bias at the Zener

V i and R 1. Determine the state of the Zener diode by removing

Example For the following Zener diode network, determine VL, VR, IZ, and PZ. Electronic

Following the suggested procedure: Since V L is less than VZ , the diode

Fixed Vi, Variable RL • To determine the minimum load resistance that will turn

• and IR remains fixed at • The Zener current Electronic Devices and

EXAMPLE • (a) For the following network , determine the range of RL and

• (a) To determine the value of RL that will turn the Zener

• For fixed values of RL, the voltage Vi must be sufficiently large

Voltage-Multiplier Circuits Voltage multiplier circuits use a combination of diodes and capacitors to step

Voltage Doubler This half-wave voltage doubler’s output can be calculated by: Vout = VC

Voltage Doubler • Positive Half-Cycle o D 1 conducts o D 2 is switched

Voltage Tripler and Quadrupler Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and

Practical Applications • Rectifier Circuits – Conversions of AC to DC for DC operated

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Chapter 2: Diode Applications

Load-Line The applied load to the circuit will normally have an important impact on the point or region of operation of a device. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Load-Line Analysis The load line (the applied load) plots all possible combinations of diode current (ID) and voltage (VD) for a given circuit. The maximum ID equals E/R, and the maximum VD equals E. The point where the load line and the characteristic curve intersect is the Q-point, which identifies ID and VD for a particular diode in a given circuit. Quiescent point (abbreviated “Qpt. ”) to reflect its “still, unmoving” Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 3 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Series Diode Configurations Forward Bias Constants • Silicon Diode: VD = 0. 7 V • Germanium Diode: VD = 0. 3 V Analysis (for silicon) • VD = 0. 7 V • VR = E – VD • ID = I R = I T = V R / R Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 4 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Series Diode Configurations Reverse Bias Diodes ideally behave as open circuits Analysis • VD = E • VR = 0 V • ID = 0 A Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 5 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

EXAMPLE For the series diode determine (a) VDQ and IDQ. (b) VR. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

EXAMPLE For the series diode configuration, determine VD, VR, and ID. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

• Since the applied voltage establishes a current in the clockwise direction to match the arrow of the symbol and the diode is in the “on” state, VD = 0. 7 V Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

EXAMPLE • Determine Vo and ID for the series circuit Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Parallel Configurations Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 12 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Example Determine the current I for the network: Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Example: Determine the voltage Vo for the network Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Half-Wave Rectification 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 0. 318 Vm, where Vm = the peak AC voltage. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 16 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

PIV (PRV) Because the diode is only forward biased for one-half of the AC cycle, it is also reverse biased for one-half cycle. It is important that the reverse breakdown voltage rating of the diode be high enough to withstand the peak, reverse-biasing AC voltage without entering the zener region. • • • PIV (or PRV) > Vm PIV = Peak inverse voltage PRV = Peak reverse voltage Vm = Peak AC voltage Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 17 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Full-Wave Rectification The rectification process can be improved by using a full-wave rectifier circuit. Full-wave rectification produces a greater DC output: • • Half-wave: Vdc = 0. 318 Vm Full-wave: Vdc = 0. 636 Vm Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 18 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Full-Wave Rectification Bridge Rectifier • • Four diodes are connected in a bridge configuration VDC = 0. 636 Vm Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 19 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Full-Wave Rectification Center-Tapped Transformer Rectifier Requires • Two diodes • Center-tapped transformer VDC = 0. 636 Vm Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 20 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Summary of Rectifier Circuits Rectifier Ideal VDC Half Wave Rectifier VDC = 0. 318 Vm Bridge Rectifier VDC = 0. 636 Vm Center-Tapped Transformer Rectifier VDC = 0. 636 Vm Realistic VDC Vm = peak of the AC voltage. In the center tapped transformer rectifier circuit, the peak AC voltage is the transformer secondary voltage to the tap. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 21 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

EXAMPLE Determine the output waveform for the following network and calculate the output dc level and the required PIV of each diode. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

For the positive region of the input voltage Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

For the negative part of the input the roles of the diodes will be interchanged and vo will appear as Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

AND/OR GATES Positive logic OR gate. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

AND/OR GATES positive logic AND gate Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

PIV For The Bridge Configuration The required PIV of each diode at the peak of the positive region of the input signal. For the indicated loop the maximum voltage across R is Vm and the PIV rating is defined by PIV Vm full-wave bridge rectifier Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

PIV For Center-tapped Transformer Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Diode Clippers Clipper is a variety of diode networks that have the ability to “clip” off a portion of the input signal without distorting the remaining part of the alternating waveform. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 30 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Series Clippers • The diode in a series clipper “clips” any voltage that does not forward bias it, such as half-wave rectifier series clippers Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Biased Clippers Adding a DC source in series with the clipping diode changes the effective forward bias of the diode. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 32 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Example Determine the output waveform for the network Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

The network will appear as below, and vo=vi +5 V. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Parallel Clippers The diode (ideal) 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. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 37 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Example Determine vo for the following network Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Summary of Clipper Circuits more… Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 40 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Summary of Clipper Circuits Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 41 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Clampers A diode and capacitor can be combined to “clamp” an AC signal to a specific DC level. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 42 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Biased Clamper Circuits The input signal can be any type of waveform such as sine, square, and triangle waves. The DC source lets you adjust the DC camping level. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 43 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

In general, the following steps may be helpful when analyzing clamping networks: 1. Start the analysis of clamping networks by considering that part of the input signal that will forward bias the diode. 2. During the period that the diode is in the “on” state, assume that the capacitor will charge up instantaneously to a voltage level determined by the network. 3. Assume that during the period when the diode is in the “off” state the capacitor will hold on to its established voltage level. 4. Throughout the analysis maintain a continual awareness of the location and reference polarity for Vo to ensure that the proper levels for Vo are obtained. 5. Keep in mind the general rule that the total swing of the total output must match the swing of the input signal. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Example Determine vo for the following network for the input indicated. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

• The analysis will begin with the period t 1 → t 2 of the input signal since the diode is in its short-circuit state as recommended by comment 1. • For this interval the output is across R, but it is also directly across the 5 -V battery the result is Vo 5 V for this interval. • Applying Kirchhoff’s voltage law around the input loop will result in • The capacitor will therefore charge up to 25 V, as stated in comment 2. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

• The open-circuit equivalent for the diode will remove the 5 -V battery from having any effect on Vo, and applying Kirchhoff’s voltage law around the outside loop of the network will result in Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Summary of Clamper Circuits Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 49 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Zener Diodes The Zener is a diode operated in reverse bias at the Zener Voltage (Vz). • When Vi VZ – The Zener is on – Voltage across the Zener is VZ – Zener current: IZ = IR – IRL – The Zener Power: PZ = VZIZ • When Vi < VZ – The Zener is off – The Zener acts as an open circuit Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 50 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

V i and R 1. Determine the state of the Zener diode by removing it from the network and calculating the voltage across the resulting open circuit. 2. Substitute the appropriate equivalent circuit and solve for the desired unknowns. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Example For the following Zener diode network, determine VL, VR, IZ, and PZ. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Following the suggested procedure: Since V L is less than VZ , the diode is in the “off” state. Substituting the open-circuit equivalent will result in; Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Fixed Vi, Variable RL • To determine the minimum load resistance that will turn the Zener diode on, simply calculate the value of RL that will result in a load voltage VL =VZ. That is, • Solving for RL, we have • Once the diode is in the “on” state, the voltage across R remains fixed at Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

• and IR remains fixed at • The Zener current Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

EXAMPLE • (a) For the following network , determine the range of RL and IL that will result in VRL being maintained at 10 V. • (b) Determine the maximum wattage rating of the diode. Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

• (a) To determine the value of RL that will turn the Zener diode on The voltage across the resistor R Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

• For fixed values of RL, the voltage Vi must be sufficiently large to turn the Zener diode on. The minimum turn-on voltage Vi Vimin is determined by Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Voltage-Multiplier Circuits Voltage multiplier circuits use a combination of diodes and capacitors to step up the output voltage of rectifier circuits. • • • Voltage Doubler Voltage Tripler Voltage Quadrupler Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 59 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Voltage Doubler This half-wave voltage doubler’s output can be calculated by: Vout = VC 2 = 2 Vm where Vm = peak secondary voltage of the transformer Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 60 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Voltage Doubler • Positive Half-Cycle o D 1 conducts o D 2 is switched off o Capacitor C 1 charges to Vm • Negative Half-Cycle o D 1 is switched off o D 2 conducts o Capacitor C 2 charges to 2 Vm Vout = VC 2 = 2 Vm Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 61 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Voltage Tripler and Quadrupler Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 62 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.

Practical Applications • Rectifier Circuits – Conversions of AC to DC for DC operated circuits – Battery Charging Circuits • Simple Diode Circuits – Protective Circuits against overcurrent – Polarity Reversal • Zener Circuits – Overvoltage Protection – Setting Reference Voltages Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 63 Copyright © 2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 • All rights reserved.