Leveraging Ham Radio for STEM G7A – G7C Practical Circuits Week 2: Ohms Law Review, Capacitance, Inductance, Semiconductors, Amplifiers.

Leveraging Ham Radio for STEM G7A – G7C Practical Circuits Week 2: Ohms Law Review, Capacitance, Inductance, Semiconductors, Amplifiers

Ohm’s Law In Practice The next series of exercises will put Ohm’s Law to use to illustrate some principles of basic electronics. As in the previous exercise you will build the circuits and insert the VOM into the circuit in the appropriate way to make current and voltage measurements. Throughout the exercise record your data so that you can compare it to calculations.

Ohm’s Law In Practice Build up the illustrated circuit.  R 1 = 1 k-ohm  R 2 = 1 k-ohm  R 3 = 2.2 k-ohm  R 4 = 300 ohm Measure the current flowing through the circuit. R1R1 R2R2 R3R3 R4R4 + -

Ohm’s Law In Practice Now move the VOM to the other side of the circuit and measure the current. The current should be the same as the previous measurement. + -

Ohm’s Law In Practice Insert the VOM at the indicated location and measure the current. There should be no surprise that the current is the same. + -

Ohm’s Law In Practice Measure the voltage across R 1. Using Ohm’s law, calculate the voltage drop across a 1K ohm resistor at the current you measured Compare the result.

Ohm’s Law In Practice In this next step, you will insert the VOM in the circuit at two places illustrated at the right as #1 and #2. Record your current readings for both places. Add the currents and compare and contrast to the current measured entering the total circuit. #1 #2

Ohm’s Law In Practice Using the current measured through #1 and the resistance value of R2, 1k ohms, calculate the voltage drop across the resistor. Likewise do the same with the current measured through #2 and the resistance value of R3, 2.2k ohms. Compare and contrast these two voltage values

Ohm’s Law In Practice Measure the voltage across the parallel resistors and record your answer. Compare and contrast the voltage measured to the voltage drop calculated.

Ohm’s Law In Practice In the next step, insert the VOM into the circuit as illustrated, measure and record the current. Compare and contrast the current measured to the total current measured in a previous step. Were there any surprises?

Ohm’s Law In Practice Using the current you just measured and the resistance of R4 (330 ohms), calculate what the voltage drop across R4 should be. Insert the VOM into the circuit as illustrated and measure the voltage. Compare and contrast the measured and calculated voltages.

Ohm’s Law In Practice There is one final measurement to complete this portion of the exercise. Insert the VOM as indicated. Recall the 3 voltages measured previously; across R 1, R 2 and R 3, and across R 4. Add these three voltages together and then compare and contrast the result with the total voltage just measured.

Ohm’s Law In Practice What you observed was: The sum of the individual currents entering a node was equal to the total current leaving a node. The sum of the voltage drops was equal to the total voltage across the circuit. This is Kirchhoff’s law and is very useful in the study of electronic circuits. You also noted that Ohm’s law applied throughout the circuit.

The Capacitor Capacitance defined Physical construction Types How construction affects values Power ratings Capacitor performance with AC and DC currents Capacitance values Numbering system Capacitors in circuits Series Parallel Mixed

The Capacitor

The Capacitor Defined A device that stores energy in electric field. Two conductive plates separated by a non conductive material. Electrons accumulate on one plate forcing electrons away from the other plate leaving a net positive charge. Think of a capacitor as very small, temporary storage battery.

The Capacitor Physical Construction Capacitors are rated by: Amount of charge that can be held. The voltage handling capabilities. Insulating material between plates.

Circuit Components  Low equivalent series resistance is an important characteristic for capacitors used to filter the DC output of a switching power supply. (G6A01)  Electrolytic capacitors are often used in power-supply circuits to filter the rectified AC. (G6A02 )  An advantage of ceramic capacitors as compared to other types of capacitors is comparatively low cost. (G6A03) Modern switching power supplies incorporate “crowbar protection” to provide overvoltage protection.

Circuit Components  High capacitance for given volume is an advantage of an electrolytic capacitor. (G6A04)  The effect of lead inductance in a capacitor used at VHF frequencies and above is that effective capacitance may be reduced because of the lead inductance. (G6A05 )  The resistance of a carbon resistor will change depending on the resistor's temperature coefficient rating if the ambient temperature is increased. (G6A06) Electrolytic Capacitors

The Capacitor Ability to Hold a Charge Ability to hold a charge depends on: Conductive plate surface area. Space between plates. Material between plates.

Charging a Capacitor

In the following activity you will charge a capacitor by connecting a power source (9 volt battery) to a capacitor. You will be using an electrolytic capacitor, a capacitor that uses polarity sensitive insulating material between the conductive plates to increase charge capability in a small physical package. Notice the component has polarity identification + or -. +

Charging a Capacitor Touch the two leads of the capacitor together. This short circuits the capacitor to make sure there is no residual charge left in the capacitor. Using your VOM, measure the voltage across the leads of the capacitor

Charging a Capacitor Wire up the illustrated circuit and charge the capacitor. Power will only have to be applied for a moment to fully charge the capacitor. Quickly remove the capacitor from the circuit and touch the VOM probes to the capacitor leads to measure the voltage. Carefully observe the voltage reading over time until the voltage is at a very low level (down to zero volts).

Discharging a Capacitor

The Capacitor Behavior in DC When connected to a DC source, the capacitor charges and holds the charge as long as the DC voltage is applied. The capacitor essentially blocks DC current from passing through.

The Capacitor Behavior in AC When AC voltage is applied, during one half of the cycle the capacitor accepts a charge in one direction. During the next half of the cycle, the capacitor is discharged then recharged in the reverse direction. During the next half cycle the pattern reverses. It acts as if AC current passes through a capacitor

The Capacitor Behavior A capacitor blocks the passage of DC current A capacitor passes AC current

The Capacitor Capacitance Value The unit of capacitance is the farad. A single farad is a huge amount of capacitance. Most electronic devices use capacitors that are a very tiny fraction of a farad. Common capacitance ranges are:  Micro 10 -6  Nano 10 -9  Pico 10 -12

The Capacitor Capacitance Value Capacitor identification depends on the capacitor type. Could be color bands, dots, or numbers. Wise to keep capacitors organized and identified to prevent a lot of work trying to re-identify the values.

Capacitors in Circuits Three physical factors affect capacitance values. Plate spacing Plate surface area Dielectric material In series, plates are far apart making capacitance less + - Charged plates far apart

Capacitors in Circuits In parallel, the surface area of the plates add up to be greater. This makes the total capacitance higher. + -

The Inductor Inductance defined Physical construction How construction affects values Inductor performance with AC and DC currents

The Inductor There are two fundamental principles of electromagnetics: 1.Moving electrons create a magnetic field. 2.Moving or changing magnetic fields cause electrons to move. An inductor is a coil of wire through which electrons move, and energy is stored in the resulting magnetic field.

The Inductor Like capacitors, inductors temporarily store energy. Unlike capacitors: Inductors store energy in a magnetic field, not an electric field. When the source of electrons is removed, the magnetic field collapses immediately.

The Inductor Inductors are simply coils of wire. Can be air wound (just air in the middle of the coil) Can be wound around a permeable material (material that concentrates magnetic fields) Can be wound around a circular form (toroid)

The Inductor Inductance is measured in Henry(s). A Henry is a measure of the intensity of the magnetic field that is produced. Typical inductor values used in electronics are in the range of millihenry (1/1000 Henry) and microhenry (1/1,000,000 Henry)

The Inductor The amount of inductance is influenced by a number of factors: Number of coil turns. Diameter of coil. Spacing between turns. Size of the wire used. Type of material inside the coil.

Circuit Components  The advantages of using a ferrite core with a toroidal inductor (G6A09):  Large values of inductance may be obtained  The magnetic properties of the core may be optimized for a specific range of frequencies  Most of the magnetic field is contained in the core All of these choices are correct.

Circuit Components  The winding axes of solenoid inductors should be placed at right angles to minimize their mutual inductance. (G6A10)  It is important to minimize the mutual inductance between two inductors to reduce unwanted coupling between circuits. (G6A11)

Circuit Components  Filter choke is a common name for an inductor used to help smooth the DC output from the rectifier in a conventional power supply. (G6A12)  An effect of inter-turn capacitance in an inductor is that the inductor may become self resonant at some frequencies. (G6A13)  The peak-inverse-voltage rating of a rectifier is the maximum voltage the rectifier will handle in the non-conducting direction. (G6B01) Capacitor: consists of metal separated by a layer(s) of a non conductor. Non-conducting region Notice Waveforms

Inductor Performance With DC Currents When a DC current is applied to an inductor, the increasing magnetic field opposes the current flow and the current flow is at a minimum. Finally, the magnetic field is at its maximum and the current flows to maintain the field. As soon as the current source is removed, the magnetic field begins to collapse and creates a rush of current in the other direction, sometimes at very high voltage.

Inductor Performance With AC Currents When AC current is applied to an inductor, during the first half of the cycle, the magnetic field builds as if it were a DC current. During the next half of the cycle, the current is reversed and the magnetic field first has to decrease the reverse polarity in step with the changing current. These forces can work against each other resulting in a lower current flow.

The Inductor Because the magnetic field surrounding an inductor can cut across another inductor in close proximity, the changing magnetic field in one can cause current to flow in the other … the basis of transformers

The Diode The semi-conductor phenomena Diode performance with AC and DC currents Diode types General purpose LED Zenier

The Diode The semi-conductor phenomena Atoms in a metal allow a “sea” of electrons that are relatively free to move about. Semiconducting materials like Silicon and Germanium have fewer free electrons. Impurities added to semiconductor material can either add free electrons or create an absence of free electrons (holes).

The Diode The semi-conductor phenomena Consider the bar of silicon at the right. One side of the bar is doped with negative material (excess electrons). The cathode. The other side is doped with positive material (excess holes). The anode In between is a no man’s land called the P-N Junction.

The Diode The semi-conductor phenomena Consider now applying a negative voltage to the anode and positive voltage to the cathode. The electrons are attracted away from the junction. This diode is reverse biased meaning no current will flow.

The Diode The semi-conductor phenomena Consider now applying a positive voltage to the anode and a negative voltage to the cathode. The electrons are forced to the junction. This diode is forward biased meaning current will flow.

The Diode Set up the illustrated circuit on the proto board. Note the cathode (banded end) of the diode. The 330 ohm resistor in the circuit is a current limiting resistor (to avoid excessive diode current). 330

The Diode Use the same circuit, but reverse the diode. Measure and record the current.

The Diode Build the illustrated circuit. Measure the voltage drop across the forward biased diode.

The Diode with AC Current If AC is applied to a diode: During one half of the cycle the diode is forward biased and current flows. During the other half of the cycle, the diode is reversed biased and current stops. This is the process of rectification, allowing current to flow in only one direction. This is used to convert AC into pulsating DC.

The Diode with AC Current Input AC Voltage Output Pulsed DC Voltage Diode conducts Diode off

The Light Emitting Diode In normal diodes, when electrons combine with holes current flows and heat is produced. With some materials, when electrons combine with holes, photons of light are emitted, this forms an LED. LEDs are generally used as indicators though they have the same properties as a regular diode.

The Light Emitting Diode Build the illustrated circuit on the proto board. The longer LED lead is the anode (positive end). Observe the diode response Reverse the LED and observe what happens. The current limiting resistor not only limits the current but also controls LED brightness. 330

Circuit Components  An LED is forward biased when emitting light. (G6C08) Array of LEDs and resistors

Circuit Components  LCDs do not emit light. Therefore, a liquid crystal display requires ambient or back lighting. (G6C09)  A computer and transceiver are two devices in an amateur radio station that might be connected using a USB interface. (G6C10) The universal serial bus (USB) has made it simple to connect your ham radio to your computer.

Zener Diode A Zener diode is designed through appropriate doping so that it conducts at a predetermined reverse voltage. The diode begins to conduct and then maintains that predetermined voltage The over-voltage and associated current must be dissipated by the diode as heat 9V4.7V

Circuit Components  The two major ratings that must not be exceeded for silicon-diode rectifiers are peak inverse voltage; average forward current. (G6B02)  The approximate junction threshold voltage of a germanium diode is 0.3 volts. (G6B03) This is the voltage drop across the diode junction when it is conducting in the forward direction.  When two or more diodes are connected in parallel to increase current handling capacity, the purpose of the resistor connected in series with each diode is to ensure that one diode doesn't carry most of the current. (G6B04)

Circuit Components  The approximate junction threshold voltage of a silicon diode is 0.7 volts. (G6B05) This is the voltage drop across the diode junction when it is conducting in the forward direction  Lower capacitance is an advantage of using a Schottky diode in an RF switching circuit as compared to a standard silicon diode. (G6B06) It is desirable to have low capacity across the diode junction in higher frequencies where the capacitive reactance forms a significant path around the diode when reverse (Back) biased in the non conductive state.  The stable operating points for a bipolar transistor used as a switch in a logic circuit are its saturation and cut-off regions. (G6B07) Saturation is where the transistor is Base biased for maximum emitter to collector current flow Cut-off is where the transistor base is biased for minimum emitter to collector current flow

The Transistor (Electronic Valves) How they work, an inside look Basic types NPN PNP The basic transistor circuits Switch Amplifier

The Transistor base collector emitter

The Transistor The base-emitter current controls the collector-base current

The Transistor

There are two basic types of transistors depending of the arrangement of the material. PNP NPN An easy phrase to help remember the appropriate symbol is to look at the arrow. PNP – pointing in proudly. NPN – not pointing in. The only operational difference is the source polarity. PNP NPN

The Transistor Switch During the next two activities you will build a transistor switch and a transistor amplifier. The pin out of the 2N3904 transistor is indicated here. C B E

The Transistor Switch Build the circuit on the proto board. Use hook up wire to serve as “switches” to connect the current to the transistor base. What happens when you first apply power when the base is left floating (not connected)? 9-volt

The Transistor Switch Make the illustrated adjustment to the circuit. Connect one end of some hook-up wire to the positive side of the 9 volt battery. Touch the other end (supply 9 volts) to the resistor in the base line and observe what happens.

The Transistor Switch Now replace the hook-up wire connection with a connection to a 1.5 volt battery as shown. What happens when +1.5 volts is applied to the base? What happens when the battery is reversed and –1.5 volts is applied to the base?

The Transistor Switch When does the transistor start to turn on? Build up the illustrated circuit with the variable resistor in the base circuit to find out.

Circuit Components  The cases of some large power transistors must be insulated from ground to avoid shorting the collector or drain voltage to ground. (G6B08)  In a MOSFET, the gate is separated from the channel with a thin insulating layer. (G6B09) Power Transistors Insulating wafer

Circuit Components  The control grid is the element of a triode vacuum tube used to regulate the flow of electrons between cathode and plate. (G6B10) H=Heater/Filament; C=Cathode; S=Screen Grid; P=Plate

Circuit Components  A Field Effect Transistor is the solid state device most like a vacuum tube in its general operating characteristics. (G6B11) In the construction of a MOSFET the gate is separated from the channel with a thin insulating layer. The Gate is similar to the grid of a tube, it controls current flow.

Circuit Components  The primary purpose of a screen grid in a vacuum tube is to reduce grid-to-plate capacitance. (G6B12)  High discharge current is an advantage of the low internal resistance of Nickel Cadmium batteries. (G6B13)  10.5 volts is the minimum allowable discharge voltage for maximum life of a standard 12 volt lead acid battery. (G6B14)  It is never acceptable to recharge a carbon-zinc primary cell. (G6B15)

Circuit Components  A linear voltage regulator, is an example of an analog integrated circuit. (G6C01) Schematic symbols and actual linear voltage regulators

Circuit Components  The term MMIC means Monolithic Microwave Integrated Circuit. (G6C02)  Low power consumption is an advantage of CMOS integrated circuits compared to TTL integrated circuits. (G6C03) CMOS is the most commonly used digital logic family of integrated circuits.  The term ROM means Read Only Memory. (G6C04) MMIC devices Signal connections

Circuit Components  ROM is characterized as “non-volatile,” meaning the stored information is maintained even if power is removed. (G6C05)  Analog is also the term that describes an integrated circuit operational amplifier. (G6C06) High power consumption is one disadvantage of an incandescent indicator compared to a LED. (G6C07) Schematic symbolIntegrated circuit

The Integrated Circuit The integrated circuit is a collection of components contained in one device that accomplishes a specific task. –Acts like a “black-box” Circuit Symbol

Protective Components – Intentional Open Circuits Fuses and circuit breakers are designed to interrupt the flow of current if the current becomes uncontrolled. –Fuses blow – one time protection. –Circuit breakers trip – can be reset and reused. Circuit Symbol

Other Circuit Symbols

Putting It All Together in a Circuit Diagram

Practical Circuits  A power supply bleeder resistor is a safety feature in that it discharges the filter capacitors. (G7A01)  The output of a rectifier connects to a filter made up of capacitors and inductors. Capacitors and inductors are used in a power-supply filter network. (G7A02) R1 and R2 are bleeder resistors

Practical Circuits  The peak-inverse-voltage across the rectifiers in a full-wave power bridge supply is equal to the normal peak output voltage of the power supply. (G7A03) Full-Wave Bridge Solid State Power Supply with pi network filter and resistive load Notice Waveforms

Practical Circuits  The peak-inverse-voltage across the rectifiers in a half-wave power supply is two times the normal output voltage of the power supply. (G7A04)  180 degrees is the portion of the AC cycle that is converted to DC by a half-wave rectifier. (G7A05) Half-wave rectifier power supply

Practical Circuits  360 degrees is the portion of the AC cycle is converted to DC by a full-wave rectifier. (G7A06)  A series of DC pulses at twice the frequency of the AC input is the output waveform of an unfiltered full-wave rectifier connected to a resistive load (G7A07) Full-wave rectifier power supply

Practical Circuits  One advantage of a switched-mode power supply as compared to a linear power supply is that high frequency operation allows the use of smaller components. (G7A08) Regulated supply showing outputs Interior view of a switched-mode power supply: A - bridge rectifier B - Input filter capacitors C - Transformer D - output filter coil E - output filter capacitors

Practical Circuits  Symbol 1 in figure G7-1 represents a field effect transistor. (G7A09) Schematic symbol for: Field Effect Transistor.

Practical Circuits  Symbol 5 in figure G7-1 represents a Zener diode. (G7A10) Schematic symbol for: Zener Diode.

Practical Circuits Symbol 2 in figure G7-1 represents an NPN junction transistor. (G7A11) Schematic symbol for: NPN Junction Transistor

Practical Circuits Symbol 6 in Figure G7-1 represents a multiple-winding transformer. (G7A12) Schematic symbol for: Multiple-winding transformer.

Practical Circuits  Symbol 7 in Figure G7-1 represents a tapped inductor. (G7A13) Schematic symbol for: Tapped Inductor.

What is the ability to store energy in an electric field called? (T5C01) A. Inductance B. Resistance C. Tolerance D. Capacitance

What is the basic unit of capacitance? (T5C02) A. The farad B. The ohm C. The volt D. The henry

What is the ability to store energy in a magnetic field called? (T5C03) A. Admittance B. Capacitance C. Resistance D. Inductance

What is the basic unit of inductance? (T5C04) A. The coulomb B. The farad C. The henry D. The ohm

What electrical component is used to oppose the flow of current in a DC circuit? (T6A01) A. Inductor B. Resistor C. Voltmeter D. Transformer

What type of component is often used as an adjustable volume control? (T6A02) A. Fixed resistor B. Power resistor C. Potentiometer D. Transformer

What electrical parameter is controlled by a potentiometer? (T6A03) A. Inductance B. Resistance C. Capacitance D. Field strength

What electrical component stores energy in an electric field? (T6A04) A. Resistor B. Capacitor C. Inductor D. Diode

What type of electrical component consists of two or more conductive surfaces separated by an insulator? (T6A05) A. Resistor B. Potentiometer C. Oscillator D. Capacitor

What type of electrical component stores energy in a magnetic field? (T6A06) A. Resistor B. Capacitor C. Inductor D. Diode

What electrical component is usually composed of a coil of wire? (T6A07) A. Switch B. Capacitor C. Diode D. Inductor

What electrical component is used to connect or disconnect electrical circuits? (T6A08) A. Zener diode B. Switch C. Inductor D. Variable resistor

What electrical component is used to protect other circuit components from current overloads? (T6A09) A. Fuse B. Capacitor C. Shield D. Inductor

What class of electronic components is capable of using a voltage or current signal to control current flow? (T6B01) A. Capacitors B. Inductors C. Resistors D. Transistors

What electronic component allows current to flow in only one direction? (T6B02) A. Resistor B. Fuse C. Diode D. Driven element

Which of these components can be used as an electronic switch or amplifier? (T6B03) A. Oscillator B. Potentiometer C. Transistor D. Voltmeter

Which of these components is made of three layers of semiconductor material? (T6B04) A. Alternator B. Bipolar junction transistor C. Triode D. Pentagrid converter

Which of the following electronic components can amplify signals? (T6B05) A. Transistor B. Variable resistor C. Electrolytic capacitor D. Multi-cell battery

How is a semiconductor diode’s cathode lead usually identified? (T6B06) A. With the word “cathode” B. With a stripe C. With the letter “C” D. All of these choices are correct

What does the abbreviation “LED” stand for? (T6B07) A. Low Emission Diode B. Light Emitting Diode C. Liquid Emission Detector D. Long Echo Delay

What does the abbreviation “FET” stand for? (T6B08) A. Field Effect Transistor B. Fast Electron Transistor C. Free Electron Transition D. Field Emission Thickness

What are the names of the two electrodes of a diode? (T6B09) A. Plus and minus B. Source and drain C. Anode and cathode D. Gate and base

Which semiconductor component has an emitter electrode? (T6B10) A. Bipolar transistor B. Field effect transistor C. Silicon diode D. Bridge rectifier

Which semiconductor component has a gate electrode? (T6B11) A. Bipolar transistor B. Field effect transistor C. Silicon diode D. Bridge rectifier

What is the term that describes a transistor’s ability to amplify a signal? (T6B12) A. Gain B. Forward resistance C. Forward voltage drop D. On resistance

What is the name for standardized representations of components in an electrical wiring diagram? (T6C01) A. Electrical depictions B. Grey sketch C. Schematic symbols D. Component callouts

Which of the following is accurately represented in electrical circuit schematic diagrams? (T6C13) A. Wire lengths B. Physical appearance of components C. The way components are interconnected D. All of these choices are correct

Which of the following devices or circuits changes an alternating current into a varying direct current signal? (T6D01) A. Transformer B. Rectifier C. Amplifier D. Reflector

Which best describes a relay? (T6D02) A. A switch controlled by an electromagnet B. A current controlled amplifier C. An optical sensor D. A pass transistor

Which of the following can be used to display signal strength on a numeric scale? (T6D04) A. Potentiometer B. Transistor C. Meter D. Relay

What component is commonly used to change 120V AC house current to a lower AC voltage for other uses? (T6D06) A. Variable capacitor B. Transformer C. Transistor D. Diode

Which of the following is commonly used as a visual indicator? (T6D07) A. LED B. FET C. Zener diode D. Bipolar transistor

Which of the following is used together with an inductor to make a tuned circuit? (T6D08) A. Resistor B. Zener diode C. Potentiometer D. Capacitor

What is the name of the device that combines several semiconductors and other components into one package? (T6D09) A. Transducer B. Multi-pole relay C. Integrated circuit D. Transformer

What is the purpose of a fuse in an electrical circuit? (T0A04) A. To prevent power supply ripple from damaging a circuit B. To interrupt power in case of overload C. To limit current to prevent shocks D. All of these choices are correct

Why is it unwise to install a 20-ampere fuse in the place of a 5 ampere fuse? (T0A05) A. The larger fuse would be likely to blow because it is rated for higher current B. The power supply ripple would greatly increase C. Excessive current could cause a fire D. All of these choices are correct

An amplifier… with a FET (Field Effect Transistor) 165

Leveraging Ham Radio for STEM G7A – G7C Practical Circuits Week 2: Ohms Law Review, Capacitance, Inductance, Semiconductors, Amplifiers.

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Leveraging Ham Radio for STEM G7A – G7C Practical Circuits Week 2: Ohms Law Review, Capacitance, Inductance, Semiconductors, Amplifiers.

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