electronic devices and circuits fy it gab

7/29/2019 Electronic Devices and Circuits Fy It Gab

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Electronic Devices and CircuitsEngineering Sciences 154Diode Applications

See nice reference onDiode Applicationsfrom the Georgia State University,Hyperphysicsproject.

Transfer Characteristic

Rectification ("frequency shifting")

Typical power supply applications
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/diodecon.html#c2http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/diodecon.html#c2http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/diodecon.html#c2http://hyperphysics.phy-astr.gsu.edu/hbase/hph.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/hph.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/hph.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/electronic/diodecon.html#c2


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Half-Wave Rectification"Figure shows a half-wave rectifier circuit. The signal is exactly the top halfof the input voltage signal, and for an ideal diode does not depend at all onthe size of the load resistor.

"The rectified signal is now a combination of an AC signal and a DC component.Generally, it is the DC part of a rectified signal that is of interest, and the un-welcomed ACcomponent is described as ripple. It is desirable to move the ripple to high frequencieswhere it is easier to remove by a low-pass filter.

"When diodes are used in small-signal applications - a few volts - their behaviour is notclosely approximated by the ideal model because of the PN turn-on voltage. The equivalentcircuit model can be used to evaluate the detailed action of the rectifier under theseconditions. During the part of the wave when the input is positive but less than the PNturn-on voltage, the model predicts no loop current and the output signal voltage istherefore zero. When the input exceeds this voltage, the output signal becomes proportionalto, or about 0.6 V lower than the source voltage."


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(source)

Op Amp solution to PN turn-on problem

(source)

Half-wave rectifier with filter capacitor or peak detector

Full-Wave Retificationo Version 1 - Center-Tap Full-Wave Rectifier

(source)
http://csr.phys.ualberta.ca/~gingrich/phys395/notes/node65.htmlhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node65.htmlhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node65.htmlhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://hyperphysics.phy-astr.gsu.edu/hbase/electronic/rectct.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/electronic/rectct.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/electronic/rectct.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/electronic/rectct.htmlhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node65.html


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o Version 2 - Bridge Full-Wave Rectifier"The diode bridge circuit shown is a full-wave rectifier. The diodesact to route the current from both halves of the AC wave through theload resistor in the same direction, and the voltage developed acrossthe load resistor becomes the rectified output signal. The diode bridge

is a commonly used circuit and is available as a four-terminalcomponent in a number of different power and voltage ratings."

(source)
http://csr.phys.ualberta.ca/~gingrich/phys395/notes/node65.htmlhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node65.htmlhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node65.htmlhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node65.html


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Go toDiode Bridge Modulesfor a collection of pdf data sheets on manyintegrated diode bridges.

Op Amp solution to PN turn-on problem

(source)

Split Power Supply
http://www.grandpower.com/indiodbri.htmlhttp://www.grandpower.com/indiodbri.htmlhttp://www.grandpower.com/indiodbri.htmlhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://www.grandpower.com/indiodbri.html


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"Often a circuit requires a power supply that provides negative voltage as well as positivevoltage. By reversing the direction of the diode and the capacitor (if it is polarized), thehalf-wave rectification circuit with low-pass filter provides a negative voltage. Similarly,reversing the direction of the diodes and capacitor in the full-wave rectified supplyproduces a negative voltage supply. A split power supply is shown in figure "

(source)

A Variety of Other Applications:

ClampAlso called a "dc restorer" in Sedra & Smith

"When a signal drives an open-ended capacitor the average voltage level on the outputterminal of the capacitor is determined by the initial charge on that terminal and maytherefore be quite unpredictable. Thus it is necessary to connect the output to ground orsome other reference voltage via a large resistor. This action drains any excess charge and

results in an average or DC output voltage of zero .

"A simple alternative method of establishing a DC reference for the output voltage is byusing a diode clamp as shown in figure . By conducting whenever the voltage at theoutput terminal of the capacitor goes negative, this circuit builds up an average charge onthe terminal that is sufficient to prevent the output from ever going negative. Positivecharge on this terminal is effectively trapped."


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(source)

(source)

Clippers/Limiters
http://csr.phys.ualberta.ca/~gingrich/phys395/notes/node69.htmlhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node69.htmlhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node69.htmlhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/opamp_diode_1.pdfhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node69.html


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"A diode clipping circuit can be used to limit the voltage swing of a signal. Figure showsa diode circuit that clips both the positive and negative voltage swings to referencesvoltages."

(source)Limiting with ordinary diodes:


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(source)

Limiting with Zener diodes:

Multiplier

Doubler - Version 1: A dc restorer followed by a peak detector
http://ourworld.compuserve.com/homepages/g_knott/elect208.htmhttp://ourworld.compuserve.com/homepages/g_knott/elect208.htmhttp://ourworld.compuserve.com/homepages/g_knott/elect208.htmhttp://ourworld.compuserve.com/homepages/g_knott/elect208.htm


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(source)

Doubler - Version 2"A voltage multiplier circuit is shown in figure. We can think of it astwo half-wave rectifier circuits in series. During the positive half-cycleone of the diodes conducts and charges a capacitor. During thenegative half-cycle the other diode conducts negatively to charge the

other capacitor. The voltage across the combination is thereforeequal to twice the peak voltage. In this type of circuit we have toassume that the load does not draw a significant charge from thecapacitors."

(source)
http://www.tpub.com/neets/book7/27m.htmhttp://www.tpub.com/neets/book7/27m.htmhttp://www.tpub.com/neets/book7/27m.htmhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node68.htmlhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node68.htmlhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node68.htmlhttp://csr.phys.ualberta.ca/~gingrich/phys395/notes/node68.htmlhttp://www.tpub.com/neets/book7/27m.htm


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(source)

Tripler


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(source)

For more on multipliers see:Cockroft-Waton Diode Voltage Multipliers

Diode Logic

"To the left (above) you see a basic Diode Logic OR gate. We'll assume that a logic 1 isrepresented by +5 volts, and a logic 0 is represented by ground, or zero volts. In this figure,

if both inputs are left unconnected or are both at logic 0, output Z will also be held at zerovolts by the resistor, and will thus be a logic 0 as well. However, if either input is raised to+5 volts, its diode will become forward biased and will therefore conduct. This in turn willforce the output up to logic 1. If both inputs are logic 1, the output will still be logic 1.Hence, this gate correctly performs a logical OR function.

"To the right (above) is the equivalent AND gate. We use the same logic levels, but thediodes are reversed and the resistor is set to pull the output voltage up to a logic 1 state. Forthis example, +V = +5 volts, although other voltages can just as easily be used. Now, if bothinputs are unconnected or if they are both at logic 1, output Z will be at logic 1. If eitherinput is grounded (logic 0), that diode will conduct and will pull the output down to logic 0

as well. Both inputs must be logic 1 in order for the output to be logic 1, so this circuitperforms the logical AND function."(source)

Standby Voltage
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/voldoub.html#c2http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/voldoub.html#c2http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/voldoub.html#c2http://www.wenzel.com/pdffiles/voltmult.pdfhttp://www.wenzel.com/pdffiles/voltmult.pdfhttp://www.play-hookey.com/digital/electronics/dl_gates.htmlhttp://www.play-hookey.com/digital/electronics/dl_gates.htmlhttp://www.play-hookey.com/digital/electronics/dl_gates.htmlhttp://www.play-hookey.com/digital/electronics/dl_gates.htmlhttp://www.wenzel.com/pdffiles/voltmult.pdfhttp://hyperphysics.phy-astr.gsu.edu/hbase/electronic/voldoub.html#c2


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(source)

Gate


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(source)

Mixer Circuits

Consider the following circuit:

Using the Shockley Diode Equation we can write


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This is a pretty complicated expression, but we can get a reasonable and usefulresult with a bit algebra and analysis. Let us assume that there are dc biases onthe signals (usual case) so that

where are fluctuations around the bias

values .

With much algebra we can show that

and

where

The important point is that the output has components
http://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/mixer_circuits/mixer_analysis.htmlhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/mixer_circuits/mixer_analysis.htmlhttp://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/diode_circuits/mixer_circuits/mixer_analysis.html

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