Circuit Components Flashcards
Resistors; capacitors; inductors; rectifiers; solid-state diodes and transistors; vacuum tubes; batteries
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
C. 10.5 volts
Discharging below this level can cause changes in the chemical nature of the cell which are irreversible, which can damage or destroy the cell.
What is an advantage of batteries with low internal resistance?
A. Long life
B. High discharge current
C. High voltage
D. Rapid recharge
B. High discharge current
High discharge current is an advantage of the low internal resistance of nickel-cadmium (NiCd) batteries. This makes them great to use in portable electronic devices and tools which require high current flow.
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
B. 0.3 volts
This threshold is the voltage over which the diode can conduct significant current. Different materials have different junction threshold voltages, so the value for each diode is determined by the properties of the material(s) used in its construction.
For example, a diode made of silicon has a junction threshold voltage of about 0.7 Volts.
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
C. High capacitance for a given volume
An advantage of electrolytic capacitors is that they have high capacitance for given volume.
These capacitors are often used in power supplies for AC voltage filtering.
They are polarized and must be placed in the circuit in the proper orientation, as reverse-voltages can cause catastrophic (explosive) failure. Bad electrolytic caps can swell and leak the electrolyte out the vent grooves notched in the top, appearing as a crusty substance. Also the electrolytic capacitors may have large variations in capacitance due to their method of manufacture.
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
C. 0.7 volts
Silly Hint:
S for Silicon, S for Seven. Also, the letter S is about 7/10 (0.7 volts) of the way through the alphabet. (As opposed to Germanium where G is about .3 the through)
Silicon has (7) letters***
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
B. The resistor’s inductance could make circuit performance unpredictable
The construction of a wire wound resistor is VERY similar to that of an inductor. So in situations where extra inductance may be an issue (such as RF circuits), they are not a good component choice.
Silly Hint: Something that is Unpredictable is usually something you do NOT choose.
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
A. Saturation and cutoff
The stable operation points for a bipolar transistor used as a switch in a logic circuit are its saturation and cut-off regions. The saturation region acts as a good “full on” switch position, whereas the cut-off region acts as a good “full off” switch position.
HINT: Famous Painter Van Gogh was BIPOLAR. He used SATURATED colors and he CUT OFF his ear.
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
D. Comparatively low cost
Silly hint: Ceramic Capacitors are Cheap
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 by 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
B. The gate is separated from the channel by a thin insulating layer
A MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is constructed so that the gate is separated from the channel with a thin insulating layer.
Why? Because the electromagnetic “field” in the name needs a dead end at the gate. The field is created when positive or negative charges accumulate on the gate electrode. The field pushes or pulls the electrons and holes within the nearby N-type and P-type materials, which opens or shuts the channel between gate and source as desired for the circuit under construction.
The pile-up of charges only works because there is nowhere for them to go (open circuit). The gate must be insulated from the rest of the transistor. If there was a short circuit, the charges would follow the path of least resistance, no charges would build up, and the “field effect” wouldn’t work correctly.
Silly hints:
The correct answer has the key word “Channel.”
This is kind of a “gotcha” question, so you can think “GATe”+”CHAnnel” for “GAT-CHA.”
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
A. Control grid
Hint: to “regulate” is to “Control” or remember that a triode tube has a control grid.
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
C. It becomes capacitive
Inductors have what is called a “Parasitic element” to them. Almost any electrical component you can think of has parasitic elements. Even the leads of a resistor have a parasitic behavior to them. The parasitic element for inductors is capacitance.
An inductor has a low distributed capacitance between terminal electrodes or the turns of a wire-wound conductor, and its inductance with such distributed capacitance resonates at a certain frequency. This frequency is called the SRF Self-Resonant Frequency, and the inductor does not function as an inductor beyond the self-resonant frequency.
When selecting an inductor for high-frequency circuits and modules, it is not enough to simply consider the required inductance. You need to take into account that the self-resonant frequency must be sufficiently higher than the usage frequency.
Capacitors are created by having metal objects in close proximity to each other, usually with a di-electric component separating them. Inductors are just a large amount of metal wire wrapped around a base. The wires interact with each other, creating a usually negligible capacitive effect, but an effect at that. If the inductor is sitting on a ground plane, the coil will even have a capacitive effect between the wires and the ground plane it is sitting upon.
To combat this, manufacturers will make their inductors with an SRF one decade above the intended frequency range (10x the frequency).
Once the inductor hits the point of its SRF, the inductive component drops to basically zero. What’s left is essentially a capacitor.
Hint: Pushing an inductor too far makes it a capacitor (the opposite)
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
A. To reduce grid-to-plate capacitance
The screen grid insulates/isolates the control grid from the plate which helps counteract the Miller effect by reducing the grid-to-plate capacitance.
Hint: SCREEN it to reduce it.
What determines the performance of a ferrite core at different frequencies?
A. Its conductivity
B. Its thickness
C. The composition, or “mix,” of materials used
D. The ratio of outer diameter to inner diameter
C. The composition, or “mix,” of materials used
Ferrites are composed of a ceramic mixture. The ratio of ceramic binder, iron powder, and other trace metals can vary, producing different electrical characteristics.
What is meant by the term MMIC?
A. Multi-Mode Integrated Circuit
B. Monolithic Microwave Integrated Circuit
C. Metal Monolayer Integrated Circuit
D. Mode Modulated Integrated Circuit
B. Monolithic Microwave Integrated Circuit
This circuit is used for amplification, mixing, or switching in circuits operating at microwave frequencies (300 MHz to 300 GHz).
Hint: The actual name almost seems one of the least likely, but try to remember that the name refers to microwave frequencies.
Hint 2: MM in Latin is two thousand (2,000), a fairly huge number. “Monolithic” means huge.
Silly Hint: When you see the “MM” in MMIC think of saying “mmm” when you smell your food “Microwaved” (Monolithic Microwave Integrated Circuit).
Which of the following is an advantage of CMOS integrated circuits compared to TTL integrated circuits?
A. Low power consumption
B. High power handling capability
C. Better suited for RF amplification
D. Better suited for power supply regulation
A. Low power consumption
CMOS - Complementary Metal Oxide Semiconductor
TTL - transistor-transistor logic
CMOS circuits use only a very small amount of current when operating. The largest amount of current is used when the circuit is switching between “On” and “Off”.
Hint: I think of it as a “Computer Mini Off Switch”, which uses very little power, like turning off the lights consumes less power.
Silly Hint: Moss can be found in Low places.
What is a typical upper frequency limit for low SWR operation of 50-ohm BNC connectors?
A. 50 MHz
B. 500 MHz
C. 4 GHz
D. 40 GHz
C. 4 GHz
A 50-ohm BNC connector has a low SWR up to 4GHz, but not up to 40GHz.
What is an advantage of using a ferrite core toroidal inductor?
A. Large values of inductance may be obtained
B. The magnetic properties of the core may be optimized for a specific range of frequencies
C. Most of the magnetic field is contained in the core
D. All these choices are correct
D. All these choices are correct
This question could be asking about a couple of things:
(1) What advantage does a toroid core provide as opposed to a straight core?
(2) What advantage does a ferrite core provide as opposed to a powdered iron core?
Based on the correct answer, it seems like it’s only asking about toroid versus straight.
Toroids have become popular because the amount of magnetic flux that leaks outside of the core itself is low, which makes it more efficient and it radiates less electromagnetic interference.
Additionally, toroid cores are a closed loop. In a straight core the magnetic field has to go pretty far from one end to enter at the other. This means that the toroid will typically produce a larger inductance.
Finally, by varying the size and thickness and characteristics of the ferrite itself, you can optimize a ferrite toroid for different frequencies.
Silly Hint: the TOROIDAL inductor gives you the TOTAL package.
What kind of device is an integrated circuit operational amplifier?
A. Digital
B. MMIC
C. Programmable Logic
D. Analog
D. Analog
Which of the following describes a type N connector?
A. A moisture-resistant RF connector useful to 10 GHz
B. A small bayonet connector used for data circuits
C. A low noise figure VHF connector
D. A nickel plated version of the PL-259
A. A moisture-resistant RF connector useful to 10 GHz
The Type N is often used for coaxial cable connections, and has a threaded plug similar to a PL-259 but with a moisture-resistant gasket. This type of connector is especially useful for antenna connections not only for its “water-tight” capabilities, but also because it has the same 50-ohm impedance as coaxial cable, and so impedances are matched.
Most manufacturers claim consistent performance up to 11 GHz and many use it up to 18 GHz.
For more info see Wikipedia: Type N connector
Silly hint: “N” for “Nautical”. (Water). Thus, associated with “water-resistant”
How is an LED biased when emitting light?
A. In the tunnel-effect region
B. At the Zener voltage
C. Reverse biased
D. Forward biased
D. Forward biased
An LED is forward biased when emitting light. In other words, the Light Emitting Diode (LED) lights up when the current flows in the forward direction through the diode PN-junction and photons are given off.
Silly Hint: The Light will lead you Forward!
How does a ferrite bead or core reduce common-mode RF current on the shield of a coaxial cable?
A. By creating an impedance in the current’s path
B. It converts common-mode current to differential mode current
C. By creating an out-of-phase current to cancel the common-mode current
D. Ferrites expel magnetic fields
A. By creating an impedance in the current’s path
The ferrite bead presents a high impedance to RF signals. As it is located on the outside of the cable, it will present that high impedance to any RF current flowing on the outer shield of the coax. It does not affect the RF current flowing in the inner core of the coax because these currents are contained within the shield braid.
Hint: Ferrite impedes the flow of the RF signal outside the shield. Silly visual: Imagine a ferret with its finger in the dam, holding back the flow.
Ferr(I)te = (I)mpedence
What is an SMA connector?
A. A type-S to type-M adaptor
B. A small threaded connector suitable for signals up to several GHz
C. A connector designed for serial multiple access signals
D. A type of push-on connector intended for high-voltage applications
B. A small threaded connector suitable for signals up to several GHz
SMA is an acronym for a SubMiniature version A.
To eliminate distractors, note that SMA does not stand for serial multiple access. Also, an SMA is a miniature connector—so not a “large bayonet connector”. Lastly, this is not a connector that is specialized for high power or high voltage.
This type of connector is usually used for smaller gauge coaxial cable. It is especially useful for handheld transceiver or other antenna connections because the SMA connector has a 50 ohm impedance, matching that of the coaxial cable, allowing for excellent performance.
Silly Hint: SMA is the the first three letters of the word “small.” There is only one choice of answers with the word “small” in it.
Which of these connector types is commonly used for low frequency or dc signal connections to a transceiver?
A. PL-259
B. BNC
C. RCA Phono
D. Type N
C. RCA Phono
