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This covers a range of components used in Ham radio.
One or more small or subscript character(s) may be appended to a parameter to indicate what it relates too. VBE or VBE; or ICE or ICE are examples. These are the base to emitter voltage and collector to emitter current. Exactly how these render in your browser may vary.
A "battery" is an assembly of two or more electro-chemical cells, which convert chemical potential energy into electromotive force. The term is however applied to single cells informally.
Rechargeable batteries are often used in Amateur radio, as they save money over buying new primary ones frequently, plus they have suitable discharge characteristics for powering larger loads.
The lead-acid battery, especially the 12 volt version will power a 100 watt mobile rig at a "field day" events, or during power failures. They have six cells. Given we wish to take these home and recharge them for the next event, they should not be discharged below 10.5 volts. In any case, the connected radios will likely perform poorly at this point. Adjustments to the exact chemistry of automotive batteries and charging systems has seen the on-charge voltage increase from around 13.8 volts to 14.4 volts over the last few decades.
After the 2004 (Boxing Day) Indian Ocean tsunami operators recovered additional batteries badly damaged vehicles. Light vehicles with a functioning engine can be used to charge 12 volt batteries.
General comments: Generic batteries for starting ICE cars, SUVs, and pick-ups typically use liquid acid as the electrolyte, in what are termed "flooded plate" batteries. These may have caps to allow the electrolyte level to be checked, and topped up with pure water. These caps also vent gases slowly. However "maintenance free" units, which include a catalyst to recombine any hydrogen and oxygen, are now very common. Electric vehicles generally also have a 12 volt battery for essential loads, necessary if the fuse on the traction battery blows; some are moving to Lithium technologies, which can reach 16 volts while charging.
Note however that heavily discharging car starting batteries significantly will reduce their life, especially if done often. Thus deep cycle batteries should be used for things like running radios during community events and emergencies, and for off-grid repeaters.
Colour-coded "Optima" batteries, with spiral-wound cells typically have both a starting capability, and a degree of deep cycle capability. They look a little like a 6-pack of canned beverages. They use "absorbent glass mat", or AGM construction, with the electrolyte absorbed into a woven material.
A less expensive marine battery may be suitable, as they are designed for both starting large or high compression engines; and for running navigation lights, radios, perhaps radar, and household loads while at anchor. Many are designed to be safe in tipped over, which does not apply to all batteries above, and if marked as such, may even be installed in any position. Yachts can experience significant angles, and can occasionally roll right over in severe storms, potentially resulting in injuries, and the need to make a distress call.
Caravan "house batteries" are also deep cycle.
Many of these are use a "gelled" electrolyte (gel-cell), or AGM construction. Another term applied to these is "SLA", or Sealed Lead Acid; as is valve regulated lead-acid (VRLA), as they do have over-pressure relief valves which prevent them bursting if abused.
There are high cost lithium based products which emulate these batteries.
With the Ni-Cad question removed, the following discussion of battery chemistry is just useful info.
Older hand-held and similar radios can be powered from NiCad (Nickel Cadmium, or NiCd) batteries. These have the benefit of high current output for their size, thanks to their low internal resistance. For the same reason, these were also used in remote-controlled cars. A development is the NiMH (Nickel - Metal Hydride) cell, often with a greater capacity. In both cases it is possible to replace cells in battery packs, or to buy replacement packs with greater capacity than the original. Europeans may have to order replacement NiCd cells from outside the European Economic Area, as Cadmium is considered toxic and is thus verboten under 2006/66/EC. While both have a nominal voltage of 1.2 volts per cell, NiMH cells have a some what different charging behaviour.
NiCads can be charged up to 2000 times; for NiMH the number is lower.
Flooded cell NiCad batteries are used for aircraft starting, and for industrial purposes. Their life can exceed 100 years with correct maintenance. Ten such cells series might make an excellent station battery.
For loose AA NiMH cells, it very much appears Ikea's LADDA cells are Panasonic eneloop low self-discharge cells, at a lower price.
Various lithium-ion technologies are used in modern handhelds, while lithium-ion remote control vehicle / aircraft packs are an option for powering mobile radios on mountain top exercises. They have a significantly better "energy density", or capacity per kilogram than lead-acid. While 4 cells in series are required for a mobile radio; two cells, providing around 7.4 volts are used in many HTs; while one 3.7 volt cell is sufficient for smaller devices, such as the Yaesu VX-3R, and the look-alikes from China.
The examiner now refers to the advantage of "batteries with low internal resistance" being that they provide a "high discharge current", rather than nominating a specific chemistry.
The downside of low internal resistance is a potentially dangerous short-circuit current.
Off the exam, but useful: Discharge rate can be expressed in amps*, or as a C rate. A 3.2 amp-hour battery rated at 3C won't be happy supplying 20 amps, but a 6 AH one rated at 5C will be fine. A 7 AH battery running a radio at 700 mA is discharging the battery at 0.1C or C/10. The same applies to charge rates and rated charge rates. In many cases the advertised capacity is at C/20, and a faster discharge means the the battery will be depleted more rapidly than the label suggests - you won't get 2 hours out of a 7 AH battery at 3.5 amps.
* 1 Ampere (Amp) is the flow of 1 Coulomb per second. This is about 6.241509×1018 electrons per second. Its symbol C is essentially unrelated to the symbol above. If a 1 Farad supercapacitor is charged to 3.3 volts, it contains 3.3 C of charge.
If you do re-cell a pack, Cadnica cells from Panasonic have a good reputation, and come in a wide range of sizes, and include tagged versions. The brand-name was transferred from Sanyo. There are also NiMH versions. Ideally you should replace using the same cell type, as things such as completion-of-charge detection may be affected.
For Australians a source is: Wagner (WES)
Many packs are built using ultrasonic welding of the plastic. Tapping along the weld line with a ball hammer is often an effective way to open the pack.
If converting between technologies, you need to ensure an appropriate battery management system module (BMS) is used - a "vent with flame" event is most undesirable.
Several of the metals used in newer batteries live on the upper-left of the periodic table, along with things like magnesium, and some react aggressively with air or water. This position means they are often light in weight. Lead is in the lower right hand side, and lead flashing on roofs / rooves can last for for centuries. Like mercury is it a toxic heavy metal. Unlike mercury, previously used in camera light meters due to its stable 1.35 volt output, and things such as life-saving maritime beacons (EPIRBs), it has not been banned (I suppose the multi-trillion dollar auto industry $₱€₳₭$ loudly).
Manganese (below) is a metal, generally not considered an excessively toxic one. The same applies to zinc, and along with nickel, none are dangerously reactive.
Rechargeable nickel-zinc (NiZn) cells, available in AA and AAA, sizes have a voltage of 1.6 volts.
Rechargeable alkaline manganese (RAM) cells are a variation on the traditional alkaline cell, with the ability to be recharged perhaps 25 times. Their only significant benefit is the 1.5 volt characteristic.
Each requires a specific charger.
Nickel oxyhydroxide battery (NiOx) is a primary or non-rechargeable cell chemistry delivering 1.7 volts. They were sold an 4-packs of AAs, aimed at the digital point-and-shoot camera user, but have been discontinued. They were certainly suitable for AA cell holders in older HTs, but many consumer devices with high current demands have now moved to lithium technologies, so I expect these cells are unlikely to return.
Old-fashioned zinc-carbon cells should never be recharged. I believe they can burst as there is no provision for gases created to escape, but they are also subject to leakage, as the zinc case is also the electrode, and it is likely that they case would be perforated by subsequent discharges, causing acid to leak out. In many cases Alkaline batteries and cells are far better value that any with "Heavy Duty" in their name, which are zinc chloride cells. That said, in the late 1980s two supermarket D-cells and a cable ran my generic brand Walkman style cassette player for weeks or months for the same cost as a pair of AA alkalines which lasted just days.
Alkaline Manganese, or "Alkaline" cells have greater capacity and a long shelf life. They are suitable for some hand-held radios, and many accessories. Ikea's cells are good value, as are those sold by the original Czech TESLA - nothing to do with the musky extremist. Duracells made in Belgium apparently do NOT leak (let the reader understand).
The 23A is a small (10.8 mm diameter × 28.5 mm length) 12 volt battery which will fit holders for the 1.5 volt N-cell (12 mm × 30.5 mm), suitable for small projects.
Lithium-iron disulfide (Li-FeS2) are costly AA and AAA cells with a 1.5 volt terminal voltage, which generally have a greater capacity than those above. Li-CuO was used in the early 1990s. These and other "Lithium metal" cells (usually in the 3 volt plus range) are primary, although some secondary versions, exist, using liquid electrolyte, or the near-fabled "solid-state electrolyte". Toyota has been promising extraordinary range with solid-state batteries, "in two years" for many years (but in the meantime, walk this way, and buy an ICE, or a pointless ICE-lite "hybrid"). 3 volt Lithium coin cells are often used for memory retention, but are useful in small, low current projects, with infrequent use. They are numbered CRxxyy, such that xx is the diameter in millimetres, and yy is the height in tenths of a mm. Thus CR2016 is 20 mm in diameter by 1.6 mm thick, the popular CR2032 3.2 mm thick. The range is 9.5 to 30 mm diameter, and 1.2 to 7.7 mm thick; with a 11.6 × 10.8 mm outlier. A few cylindrical camera batteries use a CR prefix, without complying with the coding.
Electric vehicle development may lead to some new rechargeable technologies, as may the need for grid-connected, and stationary off-grid, storage.
One may be aluminium-ion. At 2.65 volts per cell, five in series would provide a very useful 13.25 volts. Energy density is very high, but there are various challenges. Bauxite to make Aluminium (or Aluminum) is very abundant.
Sodium-ion, often marked Na+, or SIB is now receiving $billions in investment, and is in earlier stages in manufacture. With 3 to 3.3 volts per cell, 4 in series will run Amateur gear. Sodium is very common, both in land-based minerals, and in sea water. Zonergy offers rectangular cells and integrated NaESS - Sodium based Energy Storage Systems, including a system integrating PV (Solar), NA+ batteries, and an EV charger. See this PDF. Battery makers BYD and CATL have also invested significantly. AliExpress has 18650 and larger cells, especially from SEEKWATT. Sriko is a US based supplier.
Thin LFP cells also have potential for back-pack based operations. A123 Systems has some interesting cells and batteries in this style. Other Lithium types include LiFe, LiPO, NMC, LiS, and many others. See: Wikipedia: List of battery types. CSIRO and many others are working on new chemistries, physical structures, and methods.
Nickel-Iron (Ni-Fe) from the early 1900s may be making a resurgence in stationary grid storage batteries, including for longer term storage for power delivery on still and overcast days. They are 1.2 volts each, and are used in some industrial settings, and occasionally in farm off-grid installations. Low cost is the big attraction. They were designed by Edison, and used in some "Baker Electrics" cars. Hobbyists have made even their own.
Potassium-ion battery, K+, K-ion, or KIB have seen limited use, and have been available as 4.0 volt 18650 cells. Life, including yours, depends on natural K+ batteries. Fruit, vegetables, and derived products are generally good sources of potassium, also termed "Vitamin K". This includes bananas: 🍌
Round cells are sized xxyyy, where xx is the diameter in millimetres, and yyy is related to the height in millimeters, so 18650 or 1865 is 18 mm diameter, 65 mm high. 46145 is however 47 mm by 150 mm. Most in this size are Lithium-ion. While primary cells consist of a rod as one electrode, in a paste, which is in a tube which forms the other electrode; cylindrical rechargeables are in a "jelly roll" or Swiss roll spiral format, as are Li-FeS primary cells.
Magnesium (Mg) has previously been used in primary cells for military radio batteries, with reasonable cost; and in experimental secondary cells. The former developed Hydrogen gas which could blow the cover off if it was left closed with the radio running, and it was subsequently unclipped. It could potentially explode, as can H2 released by lead-acid cells.
You should remember that a diode allows current to flow in one direction, but not the other.
There are two common semiconductor materials used for signal and power diodes. The material affects the voltage at which the diodes conduct forward current. Historically, Germanium was used, for diodes and transistors. The benefit is that the forward voltage is low, 0.3 volts according to the examiners. These had limited current carrying capacity, and would fail at lower temperatures than silicon units. For the modern silicon diodes, the drop is 0.7 volts. These devices are however more rugged, with good current capacity, and tolerance of brief overloads.
Currently Germanium diodes are most often only used for things like detectors in "crystal" radios. Power rectifiers, along with many small signal applications, use silicon diodes. 1N914, or more often the 1N4148 can be used to form OR gates, or matrix, essentially a simple ROM to set channels in a 1980s two-way radio.
Non-US material tends to list 0.2 for germaniums, and 0.6, or occasionally 0.65 volts for silicon devices. These lower voltages relate to the onset of conduction, at very low forward currents. The figures in the exam relate to diodes conducting a moderate current, while at higher current they are exceeded. The voltage drop at low current also decreases with increasing temperature. While the 10¢ 1N4148 can be used experimentally for temperature measurement, the DT-670 series are professional devices.
There are valve / tube diodes, including signal level devices, power rectifiers (single and dual-anode), and high voltage units used in early CCTV / broadcast station monitors. Mercury vapour filled units were one option to rectify 25 or 50 Hz AC to DC for railway and tramway power, and for lifts / elevators. Earlier again, 25 Hz was generated to be fed around a city, to be rectified to DC via rotary convertors.
Used partly as a budget alternative to tube / valve rectifiers stacks of selenium or earlier copper oxide rectifiers were used, often appearing as a stack of painted, spaced, metal squares or discs (disks). These had a high forward voltage drop so care is needed when replacing them, but they can likely be left in place, and a modern solution (silicon diode(s), a series power resistor, and perhaps a thermistor) hidden under the chassis. Selenium units stink when they fail, and release toxic material. ☠
The Schottky diode is an improved diode, with one benefit being reduced capacitance, important for RF switching. Switching RF signals using diodes is done by biasing the diode to conduct, or not, using DC voltages.
Silicon Carbide (SiC) Schottky Diode are the newest power devices.
As you would probably know, transistors can be used as a linear device, amplifying audio or RF signals. However, you should also remember back to the Technician paper, where a transistor was used to switch a lamp. Related to this is using transistors in logic circuits, where they are switched between the saturated (fully conducting) and cut-off (open / off) modes.
Saturation is achieved by ensuring the base to emitter current is several times that required to ensure the lowest gain samples of the transistor used will cause the collector to emitter current necessary to pull the collector close to the negative rail. If we have a 12 volt rail, and a 2 kΩ resistor rail to collector, then 6mA could flow. If the resistors gain is 50 to 250, then we need several times 0.12 to flow from base to emitter, say 0.5 mA is fine. If the on voltage of the input is 6 volts, allow a generous 1 volt for VBE, and we want 0.5mA through a resister with 5 volts across it, so 10,000 is the maximum resistor value. To ensure the transistor is off, we must make sure less than 0.6 volts is present at the base when we wish the transistor not to conduct.
Field effect transistors are a family of devices with high input impedance. One kind had a metal gate insulated from the main silicon "channel" by a thin layer of silicon oxide, and this sandwich gives the name: Metal Oxide Semiconductor FET- MOSFET.
Like most FETs these have a high input impedance. They can be sensitive to static discharge.
These devices are used within many ICs, due to their energy efficiency, the most common being "CMOS", complementary metal oxide semiconductor, where these FETS actively pull the output to either the positive or negative rail. These can typically "directly drive" an LED with several milliamps, noting that "directly" means without an external transistor, rather than without a resistor.
The classic 555 plus 4017 LED chaser or dice 🎲 emulation project is a prime example of this. This can use through-hole components, or be used as surface-mount soldering training.
Power MOSFETs can be configured to acts as a series reverse polarity protection "idiot diode" on equipment such as repeaters. A low RDS translates to a forwards voltage drop less then a regular diode, down to 50 mV.
Resistors act to reduce current flow in a circuit, or in combinations perform tasks such as dividing a DC voltage or attenuating a signal. Small units typically consist or a film of a material which is a poor conductor, such as a metal alloy, or carbon. Nichrome wire, or even iron can also be used.
Accurate value, low value resistor, such as 0.01 ohms (10 mΩ) can be placed is series with a power supply. This is also termed a "shunt". For each amp 10 millivolts appears across the resistor, so 20 amps means 200 mV. Larger shunts are also used with mechanical meters, in industrial situations. Those in the hundreds of amps range consist of two terminals with metal rods or plates between them. Discrete component voltage regulator circuits can include a resistor and an additional transistor, so that the circuit can automatically limit the output current.
As most components are heated or cooled, their characteristics change, often in a fairly predictable manner. For resistors this can be an increase or a decrease in resistance, depending on the material used. Often this variation is not an issue, say just changing a power supply's voltage by a small fraction of a volt.
For things like oscillators it is a problem, as frequencies vary, but can be mitigated by things like turning mains powered test equipment on half-an-hour before using it, or using equipment with the crystal in an internal "oven" which maintains it at a specific temperature. At other times the characteristic can be used to make a sensor for a thermometer, current limiting devices, or a temperature compensation circuit.
Metal film resistors may have a 6th band, indicating "TC", or it may be available on a data-sheet.
Off the exam, metals, and thus metal film and wire-wound resistors have a positive coefficient; and carbon, germanium, and silicon have a negative coefficient, so the carbon film and carbon composition resistors have a negative coefficient.
Also off the exam, things such as ceramic capacitors change in value too. Class 1 or Class I are the most stable, suitable for resonant circuits. Class 2 or II vary more, and Class III can vary the most. The last two are suitable for less critical things, such as inter-stage coupling and bypassing noise across IC power pins.
These consist or coils of wire, usually enamelled copper wire. While they can air cored, winding them onto a core of ferrite or iron powder is common, with a toroidal shape being popular. This form allows high inductance in a small space, and tends to contain the field withing the core. Ferrite is an iron-oxide based material, and different ferrite blends are available, with different characteristics, used at different frequencies. Manganese-zinc ferrite and Nickel-zinc ferrite are examples. Air-cored inductors on a ceramic or plastic former may use stiff uninsulated wire or metal strip. Traces on a printed circuit board can be used as inductors, typically using a spiral pattern. Note that an inductor can be a single loop, or even just a U-shaped wire.
Iron powder can also be formed into small toroids, and used in RF transformers.
When any two wires are in proximity there is some capacitance between them. This includes between the windings of an inductor. Thus, as the frequency of a signal across or passing through an inductor rises there is a point where the inductance and capacitance cause the same reactance the inductor becomes "self-resonant". Above this the capacitive aspect becomes prominent.
Off the exam, a "hair-pin" shaped wire can be used as a parallel resonant circuit at several hundred MHz. Essentially, the parallel wires act as a capacitor, the loop as an inductor. This can even happen in a long, thin light-globe with a U-shaped filament, there thermionic emission occurs from the side which is most negative during the each half cycle, to the more positive side. Thus an interfering RF signal with modulated with mains hum can be generated. Such lamps were banned / discontinued as early as the 1930s to prevent this, but have reappeared as a "retro" product.
Where a metal wire is used, this has to be wound into a coil to have sufficient length to have the desired resistance.
The problem with Wire-wound resistors at radio frequencies is that they can have significant inductance, therefore potentially causing the circuit to behave in what the examiner terms an "unpredictable" manner.
Off the paper, even the spiral in a film resistor can have an inductive reactance which becomes significant at high frequencies.
While various forms are possible, a rectangular prism of ceramic material is common, filled with a cement-like material on what becomes the bottom. Common versions at 5, 10 and 20 watts take this form, the 5 watt model being around 9 × 9 × 25 mm. From 25 watts and up an aluminium cladding or heatsink is common, generally with tabs to allow them to be mounted on a heatsink. Another consists of a white ceramic tube with the wire wound over it, and a green coating. Leaving a strip bare allows a tap to be fitted, making it a large potentiometer.
There are winding patterns which reduce inductance.
Capacitors consist of two layers of conductive material, called the plates, with a layer of insulating material, called the dielectric. They can be flat; stacked; or rolled like a jelly-roll, with a second layer of insulation. You could make one from a piece of picture-frame glass with foil on each side.
There are many different materials used to make capacitors. An example is the ceramic capacitor, suitable for less demanding RF applications, and low in cost. They start at 1 pF and may reach a few microfarads. Voltage ratings are typically between 50 volts and 3kV, but values up to 50 kV ones are available. Tolerance varies between 1% and 20%. Many have an orange terra-cotta colour and appearance.
Electrolytic capacitors are available from under 1 μF to over 100,000 μF. The typical voltage ratings run from 6 to 450 volts. They are used for power supply filtering, in some audio applications, in audio and low frequency oscillators and timers, and xenon flashes and strobes.
An important characteristic is that they are polarised. This means that they can fail in many "exciting" ways, such as shorting the supply rails, having the dielectric layer break down, or overheat and go BANG, or have the body rocket off across the room, trailing caustic steam. They can generate acrid smoke, and spray caustic gunk over the PCB on failure. Over-voltage can also cause failure.
Excessive current can also stress the capacitor. For filter capacitors there may be a marking re the maximum current a power supply they are used in can be rated at, or this may be on the specification sheet for the product range.
"Electros" can vary between 20% below the marked value, and up to 80% above it. Hardly "tight tolerance".
Not on the exam, Tantalum capacitors are also nicknamed "tantrum capacitors" - they also have nasty failure modes. The upsides are good capacity for volume, and lower leakage, although RBLL electrolytics can be even better in this respect.
Not specifically discussed, silver mica capacitors are suitable for use in more demanding RF applications, and have ±1% tolerance. Some plastic film capacitors, often named for the type of plastic used, and therefore having a name starting with "poly" are suitable for audio frequencies, and may have tight tolerances.
Also not mentioned, a piece of insulated wire can be folded in half, twisted together, and soldered into the circuit, and the loop snipped away. This forms a "gimmick capacitor". 25 mm gives around 1 pF, and varying the twist or snipping a few millimetres away alters the value.
See design at: SM0VPO: Gimmick Capacitors
DIY antenna capacitor: SM0VPO: 3D Printed 10 kV Tuning Capacitor
Patches on each side of a PCB can form a capacitor, and clearly, the capacitance of traces must be taken into account at RF.
These are actual questions from the General exam pool.
G6A01
What is the minimum allowable discharge voltage for maximum life of a standard 12-volt lead-acid battery?
A. 6 volts
B. 8.5 volts
C. 10.5 volts
D. 12 volts
These batteries should not be discharged below 10.5 volts, answer C.
G6A02
What is an advantage of batteries with low internal resistance?
A. Long life
B. High discharge current
C. High voltage
D. Rapid recharge
Batteries which low internal resistance are capable of high discharge current, answer B.
NiCad cells, as used in hand-held radios and remote controlled cars of the previous decades were selected based on their ability to provide high current from a small package. The various Lithium cells generally have this benefit, be they in radios, RC cars, or the real thing.
G6A03
What is the approximate forward threshold voltage of a germanium diode?
A. 0.1 volt
B. 0.3 volts
C. 0.7 volts
D. 1.0 volts
These diodes have a low forward voltage, around 0.3 volts, answer B.
G6A04
Which of the following is characteristic of an electrolytic capacitor?
A. Tight tolerance
B. Much less leakage than any other type
C. High capacitance for a given volume
D. Inexpensive RF capacitor
They have a fairly high capacitance for their volume, making them suitable for filtering mains powered supplies, answer C.
G6A05
What is the approximate forward threshold voltage of a silicon junction diode?
A. 0.1 volt
B. 0.3 volts
C. 0.7 volts
D. 1.0 volts
This is around 0.7 volts, answer C.
G6A06
Why should wire-wound resistors not be used in RF circuits?
A. The resistor's tolerance value would not be adequate
B. The resistor's inductance could make circuit performance unpredictable
C. The resistor could overheat
D. The resistor's internal capacitance would detune the circuit
The typical wire-wound resistor has an inductance which would affect the operation of the circuit, answer B.
G6A07
What are the operating points for a bipolar transistor used as a switch?
A. Saturation and cutoff
B. The active region (between cutoff and saturation)
C. Peak and valley current points
D. Enhancement and depletion modes
Power control and logic circuits operate with the transistor at either saturation or cutoff, answer A.
Saturation means the transistor is fully on, and cutoff means fully off.
G6A08
Which of the following is characteristic of low voltage ceramic capacitors?
A. Tight tolerance
B. High stability
C. High capacitance for given volume
D. Comparatively low cost
These are affordable capacitors when a lower value devices is needed, answer D.
They are suitable for use in some RF circuits. You often get several for a dollar. High performance silvered mica units, capable of handling high RF currents, are much more costly (a few dollars each), and not available in places like Jaycar, but rather from RS or Element 14, or from RF parts specialists.
G6A09
Which of the following describes MOSFET construction?
A. The gate is formed by a back-biased junction
B. The gate is separated from the channel with a thin insulating layer
C. The source is separated from the drain by a thin insulating layer
D. The source is formed by depositing metal on silicon
MOSFETs have a gate which is insulated from the channel. The "MOS" term refers to the layering of the metal (often aluminium) gate, the insulating silicon oxide, then the semiconductor layers. Answer B.
G6A10
Which element of a vacuum tube regulates the flow of electrons between cathode and plate?
A. Control grid
B. Suppressor grid
C. Screen grid
D. Trigger electrode
Regulates? Controls? Yep, similar meanings, and control grid is correct answer, answer A.
The previous question asked about a triode, which only has a single grid, the control grid. Maybe this will help you remember.
G6A11
What happens when an inductor is operated above its self-resonant frequency?
A. Its reactance increases
B. Harmonics are generated
C. It becomes capacitive
D. Catastrophic failure is likely
An inductor consists of turns of insulated wire, and thus there is capacitance between these windings, Once a certain, self resonant, frequency is exceeded, the capacitive effect becomes the primary factor, answer C.
G6A12
What is the primary purpose of a screen grid in a vacuum tube?
A. To reduce grid-to-plate capacitance
B. To increase efficiency
C. To increase the control grid resistance
D. To decrease plate resistance
Valves with more than three electrodes, such as the tetrode and pentode (4 and 5 electrodes) have screen grids. The screen, often connected to the cathode, reduces the control grid to plate capacitance, answer A.
On to: Components 2 - Integrated Circuits, Displays & Connectors
You can find links to lots more on the Learning Material page.
Written by Julian Sortland, VK2YJS & AG6LE, October 2024.
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