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Flashcards do conjunto (24)
- 1what is the threshold voltage of the transistorThe threshold voltage of the transistor is the minimum potential difference
needed to form the conducting channel between the drain and the source. - 2when is the transitor on and offThe
the transistor is ON when the gate–source pd, VGS, is greater than the threshold voltage,VTh.
When VGS is less than VTh, the transistor is OFF because there is no effective conducting channel between the drain and the source. - 3properties of a mosfethas high input resistance, so current between the gate and source is negligible.
low/ no energy consumption when in the on and off state - 4circuit for mosfet used to switch a relay on and offCIRCUIT
- 5what can a mosfet be used asa driver
- 6why is a potential divider conected to the inputThe potential
divider ensures the MOSFET gate is at 0 V when the output of the logic gate is 0. - 7why is a reverse biased diode connected to the MOSFET relay circuitbecause to protect the relay by short-circuiting the emf induced in the device when the current is switched on or off, which would otherwise destroy the
- 8can a logic gate be used to switch the mosfet on and offyes if a potential divider is used to connect the logic gate to the MOSFET
- 9what does the relay in a MOSFET relay circuit need to have? remember can be for any electromagnetic devicemust have a small resistance so that current through the device is large enough to operate.
however if the current is too large the heating effect of the current in the device would destroy the device. - 10circuit for MOSFET acting as a nor gate (integrated circuits)nor gates in parrallel
- 11limitation of a mosfetthe source and the drain is not a perfect insulator a small leakage passes through the transistor between the drain and source
- 12draw a MOSFET and label it
- 13symbol for reverse biased diode and forward bais diode
- 14what is a zener diodeA zener diode is a semiconductor
diode that is designed and manufactured so that when it is reverse-biased, it breaks
down and conducts at a specific pd that depends on its design. - 15when the zener diode is in reverse bias it breaks down and conducts at a specific pd what is this pd calledbreakdown pd
- 16why cant ordinary semi conductor diode replace zener diodesordinary semiconductors werent made to breakdown and their break down voltage is too high for most aplications.
- 17zener diode graph
- 18what is minimum operating currentthe minimum curren at the breakdown voltage
- 19formula for maximum power ratingP = V x I
- 20the current through a zener diode must not exceedI = P / V
- 21WHY IS A RESISTOR CONNECT IN SEIES WITH A ZENER DIODEto limit the current to a maximum so that the heating effect of the current does not destroy the diode.
- 22what is a photodiodephotodiode is a diode that conducts when it is reverse-biased and light is incident on it.
- 23what is dark currentThe leakage current for zero light intensity is called the dark current.
- 24—
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- A level Physics FlashCards sobre option, criado por Mohamed Essa em 18-04-2017.
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- Mohamed Essa
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