Questions for Electronics

www.YoYoBrain.com - Accelerators for Memory and Learning Questions for electronics Category: Default - (192 questions) What electronic device is a breakover diode diac made to trigger triacs in phase-controlled circuits 3 basic options for converting single phase to static, rotary, and electronic 3 phase power Define: static phase converter simplest/lowest cost option for converting single to 3 phase electricity Nothing more than a capacitor and a potential relay comprising a starter circuit Define: rotary phase converter consists of a 3-phase motor and some way of starting it, be it a rope and pulley or a well-designed static converter automatic start circuit converts single phase to 3 phase electricity Define: variable frequency drive a box of solid-state electronics that convert 3-phase 60 Hz AC to variable frequency 3-phase. Allows motors to be driven at different speeds Define: polarized plug a plug that must be plugged in correctly to reference line on ac plug or it will harm the equipment Define: Shockley diode special purpose diode with more 2 PN junctions (four-layer diode) uses a trigger voltage to switch the diode on What is the purpose of SSIFET transistors used in microwave frequency circuits Define: latching relay a relay where one control pulse closes the switch contacts and it remains closed until another signal tells it to release Define: component placement diagram used to show where components are layed out on circuit board Define: cold solder joints a rough and grainy solder joint; source of many problems on circuits Define: triode 3 element vacumn tube that equivalent to transistor amplifier Define: tetrode 4 element vacumn tube - similar to triode with 4th element reducing capacitive interference Define: varactor diode diode that incorporates the internal capacitance of PN junction allows electrical control of capacitance and is ideal for automatically tuning systems Define: fast-recovery diode responds to very short duration spikes and is used in high-frequency applications such as TV flyback circuit Purpose of three-state LED LED with 2 separate colors that light up depending on the direction of current. 3rd state comes from AC switching back and forth so rapidly eye sees blend of 2 colors Define: nematic liquid fluid is ordinarily transparent, but when a current is passed through it, it darkens and becomes opaque What are disadvantages of LED's difficult to see when ambient light is bright, also tend to eat up a lot of current especially when many are used Define: laser diode special type of LED that creates laser from NP junction Define: Darlington transistor where the output of 1 transistor is feed into base of another transistor Define: SCR (silicon-controlled rectifier) a diode with a 3rd lead added the current will only flow when the 3rd lead has a current applied, but then will continue to flow even if current is removed from 3rd lead. Only turns off when current through diode is removed type of a switch used to control AC or DC currents, common in light dimmer switches Define: diac dual triggered diode that produces an output on each cycle 2 diodes in parallel with opposite sides; used as a trigger for triacs Define: triac dual SCR; acts like 2 separate SCRs that are connected in parallel What is unique about VMOS transistors refinement of MOSFET; can handle higher powered than MOSFET and faster switching What is the purpose of IMPATT diodes (IMPact ionization Avalanche Transit-Time) is a form of high power diode used in high-frequency electronics and microwave devices. They are typically made with silicon carbide owing to their high breakdown fields The IMPATT diode is operated under reverse bias conditions. These are set so that avalanche breakdown occurs. This occurs in the region very close to the P+ (i.e. heavily doped P region). The electric field at the p-n junction is very high because the voltage appears across a very narrow gap creating a high potential gradient. Under these circumstances any carriers are accelerated very quickly. As a result they collide with the crystal lattice and free other carriers. These newly freed carriers are similarly accelerated and collide with the crystal lattice freeing more carriers. This process gives rise to what is termed avalanche breakdown as the number of carriers multiplies very quickly. For this type of breakdown only occurs when a certain voltage is applied to the junction. Below this the potential does not accelerate the carriers sufficiently. Once the carriers have been generated the device relies on negative resistance to generate and sustain an oscillation. The effect does not occur in the device at DC, but instead, here it is an AC effect that is brought about by phase differences that are seen at the frequency of operation. When an AC signal is applied the current peaks are found to be 180 degrees out of phase with the voltage. This results from two delays which occur in the device: injection delay, and a transit time delay as the current carriers migrate or drift across the device. The voltage applied to the diode has a mean value that means the diode is on the verge of avalanche breakdown. The voltage varies as a sine wave, but the generation of carriers does not occur in unison with the voltage variations. It might be expected that it would occur at the peak voltage. This arises because the generation of carriers is not only a function of the electric field but also the number of carriers already in existence. As the electric field increases so does the number of carriers. Then even after the field has reached its peak the number of carriers still continues to grow as a result of the number of carriers already in existence. This continues until the field falls to below a critical value when the number of carriers starts to fall. As a result of this effect there is a phase lag so that the current is about 90 degrees behind the vo What is purpose of BARITT diodes microwave frequency circuits What is the nominal voltage of a photovoltaic 0.5 V cell Define: voltage follower circuit amplifier circuit with unity gain - used for impedence matching and buffering Purpose of buffer amplifier prevents a later circuit from loading the signal source Purpose of Norton amplifier amplifies the difference in applied currents (versus voltages) Function of serial-analog delay (SAD) like a bucket brigade. Instantaneous signals are passed through a string of capacitors to delay signal Purpose of majority logic circuit count number of ON versus OFF signals and output equals the majority count Purpose of Schottky TTL circuits very fast switching diodes; 3.5 times faster than TTL but power consumption only doubled Difference between Class A, B, C amplifiers Class A - amplifies whole signal; great linear response but low efficiency Class B - amplifies only half signal; higher efficiency Class C - amplifies less than one half cycle; severly distorts signal but very efficient Define: duty cycle of rectangular wave ratio between the high voltage time and low-voltage time of signal 4 types of signal modulation amplitude modulation frequency modulation phase modulation pulse code modulation Define: current gain ratio of collector current to base current amount the amplifier increases the current Define: MOSFETS metal-oxide-semiconductor field-effect transistors Define: potentiometer adjustable resistor Define: time constant of RC integrator T = R * C At T, the charge on the capacitor is 63.2% of supply voltage Define: zener breakdown voltage the voltage where the zener diode will break down and conduct in the opposite direction of polarity Define: free-running multivibrator circuit supplies a series of clock pulses Define: comparator circuit compares 2 differenct voltages and switch on or off accordingly Define: combinational logic 0's and 1's flow through a network of logic circuits as fast as the circuits will allow. They do not pause and they are not stored for further use. Define: inverters reverse the logic state of the incoming signal Define: CMOS complementary metal-oxide-semiconductor type of integrated chip Define: DIPS dual-in-line package - integrated circuit with pins off of a plastic rectangle Define: monostable multivibrator mono - singe multivibrator - circuit that flips between 2 states a monstable flips just once and only when triggered ("one-shot") Define: switch bounce when a switch is closed or open, the contacts often fail to connect or separate cleanly. They may connect several times in quick succession before firm contact or complete separation occurs. Define: inductors device formed by winding a wire into a coil; when current passed through the coil, it resists the current for a while; same when current reverses it keeps going longer Define: peta 10 to the 15th one thousand million million Define: tera 10 to the 12th one million million Define: giga 10 to the 9th one thousand million Define: nano 10 to the -9th one thousandth of one million Define: pico 10 to the -12th one millionth of one millionth Define: femto 10 to the -15th one thousandth of one millionth of one millionth Define: alto 10 to the -18th one millionth of one millionth of one millionth Define: BJT bipolar junction transistors - 2 types (NPN or PNP) Define: BUF function the output is equal to the input of signal Define: Karnaugh Maps technique for representing Boolean functions. Allows combining terms that are next to each other to make it simple to reduce the Boolean expressions Define: RS latch reset - set latch stores a value based on whether last signal was set =

Load more