A voltage regulator consisting of two diodes in series fed

An AA flashlight cell, whose Thvenin equivalent is avoltage source of 1.5 V and a resistance of 1 , is connected to the terminals of an ideal diode. Describe twopossible situations that result. What are the diode current and terminal voltage when (a) the connection isbetween the diode cathode and the positive terminal of the battery and (b) the anode and the positive terminal are connected?

For the circuits shown in Fig. P4.2 using ideal diodes, find the values of the voltages and currents indicated.

For the circuits shown in Fig. P4.3 using ideal diodes, find the values of the labeled voltages and currents

In each of the ideal-diode circuits shown in Fig. P4.4, vI is a 1-kHz, 10-V peak sine wave. Sketch the waveform resulting at vO. What are its positive and negative peak values?

The circuit shown in Fig. P4.5 is a model for a battery charger. Here vI is a 10-V peak sine wave, D1 and D2 are ideal diodes, I is a 60-mA current source, and B is a 3-V battery. Sketch and label the waveform of the battery current iB. What is its peak value? What is its average value? If the peak value of vI is reduced by 10%, what do the peak and average values of iB become?

The circuits shown in Fig. P4.6 can function as logic gates for input voltages that are either high or low. Using 1 to denote the high value and 0 to denote the low value, prepare a table with four columns including all possible input combinations and the resulting values of X and Y. What logic function is X of A and B? What logic function is Y of A and B? For what values of A and B do X and Y have the same value? For what values of A and B do X and Y have opposite values?

For the logic gate of Fig. 4.5(a), assume ideal diodes and input voltage levels of 0 V and +5 V. Find a suitable value for R so that the current required from each of the input signal sources does not exceed 0.2 mA.

Repeat Problem 4.7 for the logic gate of Fig. 4.5(b).

Assuming that the diodes in the circuits of Fig. P4.9 are ideal, find the values of the labeled voltages and currents.

Assuming that the diodes in the circuits of Fig. P4.10 are ideal, utilize Thvenins theorem to simplify the circuits and thus find the values of the labeled currents and voltages.

For the rectifier circuit of Fig. 4.3(a), let the input sine wave have 120-V rms value and assume the diode to be ideal. Select a suitable value for R so that the peak diode current does not exceed 50 mA. What is the greatest reverse voltage that will appear across the diode?

Consider the rectifier circuit of Fig. 4.3 in the event that the input source vI has a source resistance Rs. For the case Rs = R and assuming the diode to be ideal, sketch and clearly label the transfer characteristic vO versus vI.

A symmetrical square wave of 4-V peak-to-peak amplitude and zero average is applied to a circuit resembling that in Fig. 4.3(a) and employing a 100- resistor. What is the peak output voltage that results? What is the average output voltage that results? What is the peak diode current? What is the average diode current? What is the maximum reverse voltage across the diode?

Repeat Problem 4.13 for the situation in which the average voltage of the square wave is 1 V, while its peak-topeak value remains at 4 V.

Design a battery-charging circuit, resembling that in Fig. 4.4 and using an ideal diode, in which current flows to the 12-V battery 20% of the time with an average value of 100 mA. What peak-to-peak sine-wave voltage is required? What resistance is required? What peak diode current flows? What peak reverse voltage does the diode endure? If resistors can be specified to only one significant digit, and the peak-to-peak voltage only to the nearest volt, what design would you choose to guarantee the required charging current? What fraction of the cycle does diode current flow? What is the average diode current? What is the peak diode current? What peak reverse voltage does the diode endure?

The circuit of Fig. P4.16 can be used in a signalling system using one wire plus a common ground return. At any moment, the input has one of three values: +3 V, 0 V, 3 V. What is the status of the lamps for each input value? (Note that the lamps can be located apart from each other and that there may be several of each type of connection, all on one wire!)

Calculate the value of the thermal voltage, VT, at 40C, 0C, +40C, and +150C. At what temperature is VT exactly 25 mV?

At what forward voltage does a diode conduct a current equal to 1000IS? In terms of IS, what current flows in the same diode when its forward voltage is 0.7 V?

A diode for which the forward voltage drop is 0.7 V at 1.0 mA is operated at 0.5 V. What is the value of the current?

A particular diode is found to conduct 0.5 mA with a junction voltage of 0.7 V. What is its saturation current IS? What current will flow in this diode if the junction voltage is raised to 0.71 V? To 0.8 V? If the junction voltage is lowered to 0.69 V? To 0.6 V? What change in junction voltage will increase the diode current by a factor of 10?

The following measurements are taken on particular junction diodes for which V is the terminal voltage and I is the diode current. For each diode, estimate values of IS and the terminal voltage at 10% of the measured current. (a) V = 0.700 V at I = 1.00 A (b) V = 0.650 V at I = 1.00 mA (c) V = 0.650 V at I = 10 A (d) V = 0.700 V at I = 10 mA

Listed below are the results of measurements taken on several different junction diodes. For each diode, the data provided are the diode current I and the corresponding diode voltage V. In each case, estimate IS, and the diode voltage at 10I and I/10.(a) 10.0 mA, 700 mV (b) 1.0 mA, 700 mV (c) 10 A, 800 mV (d) 1 mA, 700 mV (e) 10 A, 700 mV

The circuit in Fig. P4.23 utilizes three identical diodes having IS = 1016 A. Find the value of the current I required to obtain an output voltage VO = 2.4 V. If a current of 1 mA is drawn away from the output terminal by a load, what is the change in output voltage?

A junction diode is operated in a circuit in which it is supplied with a constant current I. What is the effect on the forward voltage of the diode if an identical diode is connected in parallel?

In the circuit shown in Fig. P4.25, D1 has 10 times the junction area of D2. What value of V results? To obtain a value for V of 50 mV, what current I2 is needed?

For the circuit shown in Fig. P4.26, both diodes are identical. Find the value of R for which V = 80 mV.

A diode fed with a constant current I = 1 mA has a voltage V = 690 mV at . Find the diode voltage at and at

In the circuit shown in Fig. P4.28, D1 is a large-area, high-current diode whose reverse leakage is high and independent of applied voltage, while D2 is a much smaller, low-current diode. At an ambient temperature of 20C, resistor R1 is adjusted to make VR1 = V2 = 520 mV. Subsequent measurement indicates that R1 is 520 k. What do you expect the voltages VR1 and V2 to become at 0C and at 40C?

When a 15-A current is applied to a particular diode, it is found that the junction voltage immediately becomes 700 mV. However, as the power being dissipated in the diode raises its temperature, it is found that the voltage decreases and eventually reaches 600 mV. What is the apparent rise in junction temperature? What is the power dissipated in the diode in its final state? What is the temperature rise per watt of power dissipation? (This is called the thermal resistance.)

A designer of an instrument that must operate over a wide supply-voltage range, noting that a diodes junction-voltage drop is relatively independent of junction current, considers the use of a large diode to establish a small relatively constant voltage. A power diode, for which the nominal current at 0.8 V is 10 A, is available. If the current source feeding the diode changes in rhe range 0.5 mA to 1.5 mA and if, in addition, the temperature changes by 25C, what is the expected range of diode voltage?

As an alternative to the idea suggested in Problem 4.30, the designer considers a second approach to producing a relatively constant small voltage from a variable current supply: It relies on the ability to make quite accurate copies of any small current that is available (using a process called current mirroring). The designer proposes to use this idea to supply two diodes of different junction areas with the same current and to measure their junction-voltage difference. Two types of diodes are available; for a forward voltage of 700 mV, one conducts 0.1 mA, while the other conducts 1 A. Now, for identical currents in the range of 0.5 mA to 1.5 mA supplied to each, what range of difference voltages result? What is the effect of a temperature change of 25C on this arrangement?

Consider the graphical analysis of the diode circuit of Fig. 4.10 with VDD = 1 V, R = 1 k, and a diode having IS = 1015 A. Calculate a small number of points on the diode characteristic in the vicinity of where you expect the load line to intersect it, and use a graphical process to refine your estimate of diode current. What value of diode current and voltage do you find? Analytically, find the voltage corresponding to your estimate of current. By how much does it differ from the graphically estimated value?

Use the iterative-analysis procedure to determine the diode current and voltage in the circuit of Fig. 4.10 for VDD = 1 V, R = 1 k, and a diode having IS = 1015 A.

A 1-mA diode (i.e., one that has vD = 0.7 V at iD = 1 mA) is connected in series with a 200- resistor to a 1.0-V supply. (a) Provide a rough estimate of the diode current you would expect. (b) Estimate the diode current more closely using iterative analysis.

Assuming the availability of diodes for which vD = 0.7 V at iD = 1 mA, design a circuit that utilizes four diodes connected in series, in series with a resistor R connected to a 10-V power supply. The voltage across the string of diodes is to be 3.0 V.

A diode operates in a series circuit with R and V. A designer, considering using a constant-voltage model, is uncertain whether to use 0.7 V or 0.6 V for VD. For what value of V is the difference in the calculated values of current only 1%? For V = 2 V and R = 1 k, what two currents would result from the use of the two values of VD? What is their percentage difference?

A designer has a supply of diodes for which a current of 2 mA flows at 0.7 V. Using a 1-mA current source, the designer wishes to create a reference voltage of 1.25 V. Suggest a combination of series and parallel diodes that will do the job as well as possible. How many diodes are needed? What voltage is actually achieved?

Solve the problems in Example 4.2 using the constantvoltage-drop (VD = 0.7 V) diode model.

For the circuits shown in Fig. P4.2, using the constant-voltage-drop (VD = 0.7 V) diode model, find the voltages and currents indicated.

For the circuits shown in Fig. P4.3, using the constant-voltage-drop (VD = 0.7 V) diode model, find the voltages and currents indicated.

For the circuits in Fig. P4.9, using the constant-voltagedrop (VD = 0.7 V) diode model, find the values of the labeled currents and voltages.

For the circuits in Fig. P4.10, utilize Thvenins theorem to simplify the circuits and find the values of the labeled currents and voltages. Assume that conducting diodes can be represented by the constant-voltage-drop model (VD = 0.7 V).

Repeat Problem 4.11, representing the diode by the constant-voltage-drop (VD = 0.7 V) model. How different is the resulting design?

The small-signal model is said to be valid for voltage variations of about 5 mV. To what percentage current change does this correspond? (Consider both positive and negative signals.) What is the maximum allowable voltage signal (positive or negative) if the current change is to be limited to10%?

In a particular circuit application, ten 20-mA diodes (a 20-mA diode is a diode that provides a 0.7-V drop when the current through it is 20 mA) connected in parallel operate at a total current of 0.1 A. For the diodes closely matched, what current flows in each? What is the corresponding small-signal resistance of each diode and of the combination? Compare this with the incremental resistance of a single diode conducting 0.1 A. If each of the 20-mA diodes has a series resistance of 0.2 associated with the wire bonds to the junction, what is the equivalent resistance of the 10 parallel-connected diodes? What connection resistance would a single diode need in order to be totally equivalent? (Note: This is why the parallel connection of real diodes can often be used to advantage.)

In the circuit shown in Fig. P4.46, I is a dc current and vs is a sinusoidal signal. Capacitors C1 and C2 are very large; their function is to couple the signal to and from the diode but block the dc current from flowing into the signal source or the load (not shown). Use the diode small-signal model to show that the signal component of the output voltage is If vs = 10 mV, find vo for I = 1 mA, 0.1 mA, and 1 A. Let Rs = 1 k. At what value of I does vo become one-half of vs? Note that this circuit functions as a signal attenuator with the attenuation factor controlled by the value of the dc current I.

In the attenuator circuit of Fig. P4.46, let Rs = 10 k. The diode is a 1-mA device; that is, it exhibits a voltage drop of 0.7 V at a dc current of 1 mA. For small input signals, what value of current I is needed for 0.50? 0.10? 0.01? 0.001? In each case, what is the largest input signal that can be used while ensuring that the signal component of the diode current is limited to 10% of its dc current? What output signals correspond?

In the capacitor-coupled attenuator circuit shown in Fig. P4.48, I is a dc current that varies from 0 mA to 1 mA, and C1 and C2 are large coupling capacitors. For very small input signals, so that the diodes can be representedby their small-signal resistances rd1 and rd2, show that and hence that , where I is in mA. Find for I = 0 A, 1 A, 10 A, 100 A, 500 A, 600 A, 900 A, 990 A, and 1 mA.

In the circuit shown in Fig. P4.49, diodes D1 through D4 are identical and each exhibits a voltage drop of 0.7 V at a 1-mA current.(a) For small input signals (e.g., 10 mV peak), find values of the small-signal transmission for various values of I : 0 A, 1 A, 10 A, 100 A, 1 mA, and 10 mA. (b) For a forward-conducting diode, what is the largest signal-voltage magnitude that it can support while the corresponding signal current is limited to 10% of the dc bias current. Now, for the circuit in Fig. P4.49, for 10-mV peak input, what is the smallest value of I for which the diode currents remain within 10% of their dc value? (c) For I = 1 mA, what is the largest possible output signal for which the diode currents deviate by at most 10% of their dc values? What is the corresponding peak input? What is the total current in each diode?

In Problem 4.49 we investigated the operation of the circuit in Fig. P4.49 for small input signals. In this problem we wish to find the voltage transfer characteristic (VTC) versus for for the case I = 1 mA and each of the diodes exhibits a voltage drop of 0.7 V at a current of 1 mA. Toward this end, use the diode exponential characteristic to construct a table that gives the values of: the current in the 10-k resistor, the current in each of the four diodes, the voltage drop across each of the four diodes, and the input voltage , for , +1 V, +2 V, +5 V, +9 V, +9.9 V, +9.99 V, +10.5 V, +11 V, and +12 V. Use these data, with extrapolation to negative values of and , to sketch the required VTC. Also sketch the VTC that results if I is reduced to 0.5 mA.

In the circuit shown in Fig. P4.51, I is a dc current and vi is a sinusoidal signal with small amplitude (less than 10 mV) and a frequency of 100 kHz. Representing the diode by its small-signal resistance rd, which is a function of I, sketch the circuit for determining the sinusoidal output voltage Vo, and thus find the phase shift between Vi and Vo. Find the value of I that will provide a phase shift of 45, and find the range of phase shift achieved as I is varied over the range of 0.1 times to 10 times this value.

Consider the voltage-regulator circuit shown in Fig. P4.52. The value of R is selected to obtain an output voltage VO (across the diode) of 0.7 V. (a) Use the diode small-signal model to show that the change in output voltage corresponding to a change of 1 V in V+ is This quantity is known as the line regulation and is usually expressed in mV/V. (b) Generalize the expression above for the case of m diodes connected in series and the value of R adjusted so that the voltage across each diode is 0.7 V (and VO = 0.7m V). (c) Calculate the value of line regulation for the case V+ = 10 V (nominally) and (i) m = 1 and (ii) m = 3.

Consider the voltage-regulator circuit shown in Fig P4.52 under the condition that a load current IL is drawn from the output terminal. (a) If the value of IL is sufficiently small that the corresponding change in regulator output voltage VO is small enough to justify using the diode small-signal model, show that This quantity is known as the load regulation and is usually expressed in mV/mA. (b) If the value of R is selected such that at no load the voltage across the diode is 0.7 V and the diode current is ID, show that the expression derived in (a) becomes Select the lowest possible value for ID that results in a load regulation 5 mV/mA. If V+ is nominally 10 V, what value of R is required? Also, specify the diode required in terms of its IS. (c) Generalize the expression derived in (b) for the case of m diodes connected in series and R adjusted to obtain VO = 0.7m V at no load.

Design a diode voltage regulator to supply 1.5 V to a 150- load. Use two diodes specified to have a 0.7-V drop at a current of 10 mA. The diodes are to be connected to a +5-V supply through a resistor R. Specify the value for R. What is the diode current with the load connected? What is the increase resulting in the output voltage when the load is disconnected? What change results if the load resistance is reduced to 100 ? To 75 ? To 50 ? (Hint: Use the smallsignal diode model to calculate all changes in ouput voltage.)

A voltage regulator consisting of two diodes in series fed with a constant-current source is used as a replacement for a single carbon-zinc cell (battery) of nominal voltage 1.5 V. The regulator load current varies from 2 mA to 7 mA. Constant-current supplies of 5 mA, 10 mA, and 15 mA are available. Which would you choose, and why? What change in output voltage would result when the load current varies over its full range?

A particular design of a voltage regulator is shown in Fig. P4.56. Diodes D1 and D2 are 10-mA units; that is, each has a voltage drop of 0.7 V at a current of 10 mA. Use the diode exponential model and iterative analysis to answer the following questions: (a) What is the regulator output voltage VO with the 150- load connected? (b) Find VO with no load. (c) With the load connected, to what value can the 5-V supply be lowered while maintaining the loaded output voltage within 0.1 V of its nominal value? (d) What does the loaded output voltage become when the 5-V supply is raised by the same amount as the drop found in (c)? (e) For the range of changes explored in (c) and (d), by what percentage does the output voltage change for each percentage change of supply voltage in the worst case?

Partial specifications of a collection of zener diodes are provided below. For each, identify the missing parameter, and estimate its value. Note from Fig. 4.17 that (a) VZ = 10.0 V, VZK = 9.6 V, and IZT = 50 mA (b) IZT = 10 mA, VZ = 9.1 V, and rz = 30 (c) rz = 2 , VZ = 6.8 V, and VZK = 6.6 V (d) VZ = 18 V, IZT = 5 mA, and VZK = 17.6 V (e) IZT = 200 mA, VZ = 7.5 V, and rz = 1.5 Assuming that the power rating of a breakdown diode is established at about twice the specified zener current (IZT), what is the power rating of each of the diodes described above?

A designer requires a shunt regulator of approximately 20 V. Two kinds of zener diodes are available: 6.8-V devices with rz of 10 and 5.1-V devices with rz of 30 . Forthe two major choices possible, find the load regulation. In this calculation neglect the effect of the regulator resistance R.

A shunt regulator utilizing a zener diode with an incremental resistance of 5 is fed through an 82- resistor. If the raw supply changes by 1.0 V, what is the corresponding change in the regulated output voltage?

A 9.1-V zener diode exhibits its nominal voltage at a test current of 28 mA. At this current the incremental resistance is specified as 5 . Find VZ0 of the zener model. Find the zener voltage at a current of 10 mA and at 100 mA.

Design a 7.5-V zener regulator circuit using a 7.5-V zener specified at 12 mA. The zener has an incremental resistance rz = 30 and a knee current of 0.5 mA. The regulator operates from a 10-V supply and has a 1.2-k load. What is the value of R you have chosen? What is the regulator output voltage when the supply is 10% high? Is 10% low? What is the output voltage when both the supply is 10% high and the load is removed? What is the smallest possible load resistor that can be used while the zener operates at a current no lower than the knee current while the supply is 10% low? What is the load voltage in this case?

Provide two designs of shunt regulators utilizing the 1N5235 zener diode, which is specified as follows: VZ = 6.8 V and rz = 5 for IZ = 20 mA; at IZ = 0.25 mA (nearer the knee), rz = 750 . For both designs, the supply voltage is nominally 9 V and varies by 1 V. For the first design, assume that the availability of supply current is not a problem, and thus operate the diode at 20 mA. For the second design, assume that the current from the raw supply is limited, and therefore you are forced to operate the diode at 0.25 mA. For the purpose of these initial designs, assume no load. For each design find the value of R and the line regulation.

A zener shunt regulator employs a 9.1-V zener diode for which VZ = 9.1 V at IZ = 9 mA, with rz = 30 and IZK = 0.3 mA. The available supply voltage of 15 V can vary as much as 10%. For this diode, what is the value of VZ0? For a nominal load resistance RL of 1 k and a nominal zener current of 10 mA, what current must flow in the supply resistor R? For the nominal value of supply voltage, select a value for resistor R, specified to one significant digit, to provide at least that current. What nominal output voltage results? For a 10% change in the supply voltage, what variation in output voltage results? If the load current is reduced by 50%, what increase in VO results? What is the smallest value of load resistance that can be tolerated while maintaining regulation when the supply voltage is low? What is the lowest possible output voltage that results? Calculate values for the line regulation and for the load regulation for this circuit using the numerical results obtained in this problem.

It is required to design a zener shunt regulator to provide a regulated voltage of about 10 V. The available 10-V, 1-W zener of type 1N4740 is specified to have a 10-V drop at a test current of 25 mA. At this current, its rz is 7 . The raw supply, VS, available has a nominal value of 20 V but can vary by as much as 25%. The regulator is required to supply a load current of 0 mA to 20 mA. Design for a minimum zener current of 5 mA. (a) Find VZ0. (b) Calculate the required value of R. (c) Find the line regulation. What is the change in VO expressed as a percentage, corresponding to the 25% change in VS? (d) Find the load regulation. By what percentage does VO change from the no-load to the full-load condition? (e) What is the maximum current that the zener in your design is required to conduct? What is the zener power dissipation under this condition?

Consider the half-wave rectifier circuit of Fig. 4.21(a) with the diode reversed. Let vS be a sinusoid with 12-V peak amplitude, and let R = 1.5 k. Use the constant-voltagedrop diode model with VD = 0.7 V. (a) Sketch the transfer characteristic. (b) Sketch the waveform of vO. (c) Find the average value of vO. (d) Find the peak current in the diode. (e) Find the PIV of the diode.

Using the exponential diode characteristic, show that for vS and vO both greater than zero, the circuit of Fig. 4.21(a) has the transfer characteristic where vS and vO are in volts and R is in kilohms. Note that this relationship can be used to obtain the voltage transfer characteristic vO vs vS by finding vS corresponding to various values of vO.

Consider a half-wave rectifier circuit with a triangular-wave input of 5-V peak-to-peak amplitude and zero average, and with R = 1 k. Assume that the diode can be represented by the constant-voltage-drop model with VD = 0.7 V. Find the average value of vO.

A half-wave rectifier circuit with a 1-k load operates from a 120-V (rms) 60-Hz household supply through a 10-to-1 step-down transformer. It uses a silicon diode that can be modeled to have a 0.7-V drop for any current. What is the peak voltage of the rectified output? For what fraction of the cycle does the diode conduct? What is the average output voltage? What is the average current in the load?

A full-wave rectifier circuit with a 1-k load operates from a 120-V (rms) 60-Hz household supply through a 5-to1 transformer having a center-tapped secondary winding. It uses two silicon diodes that can be modeled to have a 0.7-V drop for all currents. What is the peak voltage of the rectified output? For what fraction of a cycle does each diode conduct? What is the average output voltage? What is the average current in the load?

A full-wave bridge rectifier circuit with a 1-k load operates from a 120-V (rms) 60-Hz household supply through a 10-to-1 step-down transformer having a single secondary winding. It uses four diodes, each of which can be modeled to have a 0.7-V drop for any current. What is the peak value of the rectified voltage across the load? For what fraction of a cycle does each diode conduct? What is the average voltage across the load? What is the average current through the load?

It is required to design a full-wave rectifier circuit using the circuit of Fig. 4.22 to provide an average output voltage of: (a) 10 V (b) 100 V In each case find the required turns ratio of the transformer. Assume that a conducting diode has a voltage drop of 0.7 V. The ac line voltage is 120 V rms.

Repeat Problem 4.71 for the bridge rectifier circuit of Fig. 4.23.

Consider the full-wave rectifier in Fig. 4.22 when the transformer turns ratio is such that the voltage across the entire secondary winding is 24 V rms. If the input ac line voltage (120 V rms) fluctuates by as much as 10%, find the required PIV of the diodes. (Remember to use a factor of safety in your design.)

The circuit in Fig. P4.74 implements a complementary-output rectifier. Sketch and clearly label the waveforms of and Assume a 0.7-V drop across each conducting diode. If the magnitude of the average of each output is to be 15 V, find the required amplitude of the sine wave across the entire secondary winding. What is the PIV of each diode?

Augment the rectifier circuit of Problem 4.68 with a capacitor chosen to provide a peak-to-peak ripple voltage of (i) 10% of the peak output and (ii) 1% of the peak output. In each case: (a) What average output voltage results? (b) What fraction of the cycle does the diode conduct? (c) What is the average diode current? (d) What is the peak diode current?

Repeat Problem 4.75 for the rectifier in Problem 4.69.

Repeat Problem 4.75 for the rectifier in Problem 4.70.

It is required to use a peak rectifier to design a dc power supply that provides an average dc output voltage of 15 V on which a maximum of 1-V ripple is allowed. The rectifier feeds a load of 150 . The rectifier is fed from the line voltage (120 V rms, 60 Hz) through a transformer. The diodes available have 0.7-V drop when conducting. If the designer opts for the half-wave circuit: (a) Specify the rms voltage that must appear across the transformer secondary. (b) Find the required value of the filter capacitor. (c) Find the maximum reverse voltage that will appear across the diode, and specify the PIV rating of the diode. (d) Calculate the average current through the diode during conduction. (e) Calculate the peak diode current.

Repeat Problem 4.78 for the case in which the designer opts for a full-wave circuit utilizing a center-tapped transformer.

Repeat Problem 4.78 for the case in which the designer opts for a full-wave bridge rectifier circuit.

Consider a half-wave peak rectifier fed with a voltage vS having a triangular waveform with 20-V peak-topeak amplitude, zero average, and 1-kHz frequency. Assume that the diode has a 0.7-V drop when conducting. Let the load resistance R = 100 and the filter capacitor C = 100 F. Find the average dc output voltage, the time interval during which the diode conducts, the average diode current during conduction, and the maximum diode current.

Consider the circuit in Fig. P4.74 with two equal filter capacitors placed across the load resistors R. Assume that the diodes available exhibit a 0.7-V drop when conducting. Design the circuit to provide 15-V dc output voltages with a peak-to-peak ripple no greater than 1 V. Each supply should be capable of providing 200 mA dc current to its load resistor R. Completely specify the capacitors, diodes and the transformer.

The op amp in the precision rectifier circuit of Fig. P4.83 is ideal with output saturation levels of 12 V. Assume that when conducting the diode exhibits a constant voltage drop of 0.7 V. Find v, vO, and vA for: (a) vI = +1 V (b) vI = +2 V (c) vI = 1 V (d) vI = 2 V Also, find the average output voltage obtained when vI is a symmetrical square wave of 1-kHz frequency, 3-V amplitude, and zero average.

The op amp in the circuit of Fig. P4.84 is ideal with output saturation levels of 12 V. The diodes exhibit a constant 0.7-V drop when conducting. Find v, vA, and vO for: (a) vI = +1 V (b) vI = +2 V (c) vI = 1 V (d) vI = 2 V

Sketch the transfer characteristic vO versus vI for the limiter circuits shown in Fig. P4.85. All diodes begin conducting at a forward voltage drop of 0.5 V and have voltage drops of 0.7 V when conducting a current iD  1 mA.

The circuits in Fig. P4.85(a) and (d) are connected as follows: The two input terminals are tied together, and the two output terminals are tied together. Sketch the transfer characteristic of the circuit resulting, assuming that the cut in voltage of the diodes is 0.5 V and their voltage drop when conducting a current iD  1 mA is 0.7 V.

Repeat Problem 4.86 for the two circuits in Fig. P4.85(a) and (b) connected together as follows: The two input terminals are tied together, and the two output terminals are tied together.

Sketch and clearly label the transfer characteristic of the circuit in Fig. P4.88 for 20 V  vI  +20 V. Assume that the diodes can be represented by the constant-voltage drop model with VD = 0.7 V. Also assume that the zener voltage is 8.2 V and that rz is negligibly small.

Plot the transfer characteristic of the circuit in Fig.P4.89 by evaluating vI corresponding to vO = 0.5 V, 0.6 V, 0.7 V, 0.8 V, 0 V, 0.5 V, 0.6 V, 0.7 V, and 0.8 V. Assume that the diodes have 0.7-V drops at 1-mA currents. Characterize the circuit as a hard or soft limiter. What is the value of K? Estimate L+ and L.

Design limiter circuits using only diodes and 10-k resistors to provide an output signal limited to the range: (a) 0.7 V and above (b) 2.1 V and above (c) 1.4 V Assume that each diode has a 0.7-V drop when conducting.

Design a two-sided limiting circuit using a resistor, two diodes, and two power supplies to feed a 1-k load with nominal limiting levels of 3 V. Use diodes modeled by a constant 0.7 V. In the nonlimiting region, the voltage gain should be at least 0.95 V/V.

In the circuit shown in Fig. P4.92, the diodes exhibit a 0.7-V drop at 0.1 mA. For inputs over the range of 5 V, provide a calibrated sketch of the voltages at outputs B and C versus vA. For a 5-V peak, 100-Hz sinusoid applied at A, sketch the signals at nodes B and C.

Sketch and label the voltage transfer characteristic vO versus vI of the circuit shown in Fig. P4.93 over a 10-V range of input signals. All diodes are 1-mA units (i.e., each exhibits a 0.7-V drop at a current of 1 mA). What are the slopes of the characteristic at the extreme 10-V levels?

A clamped capacitor using an ideal diode with cathode grounded is supplied with a sine wave of 10-V rms. What is the average (dc) value of the resulting output?

For the circuits in Fig. P4.95, each utilizing an ideal diode (or diodes), sketch the output for the input shown. Label the most positive and most negative output levels. Assume CR  T.