E-MOSFET Flashcards
E-MOSFET
Enhancement Mode - Metal Oxide
Semiconductor Field Effect Transistor
A ____________ is used as the foundation on which the device is constructed.
N-Channel E-MOSFET Construction
p-type substrate
The ________ and ________ terminals are connected through metallic contacts to n-doped regions.
N-Channel E-MOSFET Construction
Drain (D) and Source (S)
The ________________ between two n-doped regions is the primary difference between depletion and enhancement type MOSFET.
N-Channel E-MOSFET Construction
absence of channel
The ________ isolate the gate from the region between the source and drain.
N-Channel E-MOSFET Construction
SiO2 layer
when VGS=0V and VDS=0, the absence of channel between drain and source will result in __________.
N-Channel E-MOSFET Construction (Basic Operation)
zero current
when VGS=0 and VDS is some positive voltage, there exist ____________ biased junction between the n-doped regions and p-substrate and absence of channel between source and drain which cause zero current to flow.
N-Channel E-MOSFET Construction (Basic Operation)
two reversed
Thus, when VGS=0 and voltage VDS is applied across drain to source terminals, the absence of channel will result in ________________ as against the ________________ where ID=IDSS when VGS=0.
N-Channel E-MOSFET Construction (Basic Operation)
zero drain current, depletion type MOSFET
When VGS and VDS are set to some positive voltages, then the positive potential get established at ________ and the ________ with respect to the ________.
N-Channel E-MOSFET Construction (Basic Operation)
drain, gate, source
The positive potential at gate will repel the holes in ____________ along the edge of the SiO2 layer however the electrons which is ____________ in p-substrate will be attracted to the ________________ and get accumulated in the region near the surface of the SiO2 layer.
N-Channel E-MOSFET Construction (Basic Operation)
p-type substrate, minority carrier, positive gate
The insulating SiO2 layer prevent the electrons being _________________________.
N-Channel E-MOSFET Construction (Basic Operation)
absorbed by positive gate
As VGS increases, the concentration of___________ increases such that a channel is induced between drain and source which allow flow of electrons from drain to source hence the flow of ____________.
N-Channel E-MOSFET Construction (Basic Operation)
electrons, drain current
N-Channel E-MOSFET Construction (Basic Operation)
The level of VGS that starts flow of current is called ____________ VGS(th) ot VT. For N-type MOSFET it is referred to _______
threshold voltage, VTN
Since the channel is not in existent with VGS=0 and enhance by the application of positive VGS, this type of MOSFET is called an __________________.
N-Channel E-MOSFET Construction (Basic Operation)
enhancement mode MOSFET
Both the depletion and enhancement type MOSFETs have ________________.
N-Channel E-MOSFET Construction (Basic Operation)
enhancement region
The depletion type MOSFETs can operate in both depletion and enhancement regions whereas enhancement type MOSFET can only operate in ___________________.
N-Channel E-MOSFET Construction (Basic Operation)
enhancement regions
With a fixed VDS drain-source voltage connected across the ________, we can plot the values of drain current, ID with varying values of VGS to obtain a graph of the MOSFET’s forward DC characteristics. These characteristics give the ____________________, gm of the transistor.
N-channel E-MOSFET I-V Characteristics
E-MOSFET, transconductance
when VGS>VTN, application of a small VDS causes a current ID to flow through an ________________ which increases with increase in _____.
N-Channel E-MOSFET Construction (Basic Operation: Applying a small VDS)
induced channel, VDS
An E-MOSFET with a small VDS is applied acts as a ____________ whose value is determined by _____.
N-Channel E-MOSFET Construction (Basic Operation: Applying a small VDS)
resistance, VGS
when VGS<VTN, ID=___, R=_______
N-Channel E-MOSFET Construction (Basic Operation: Applying a small VDS)
ID=0, R=infinity
When VGS>VTN, a ________ is induced causing flow of electrons, hence flow of ID, making R __________.
N-Channel E-MOSFET Construction (Basic Operation: Applying a small VDS)
channel, finite
as VGS increases, free electrons increases, drain current increases and ____ decreases.
N-Channel E-MOSFET Construction (Basic Operation: Applying a small VDS)
R
The dashed line between the source and drain in enhancement type MOSFET reflects that ____________ is physically constructed between source to drain. Channel get induced when _________.
Symbol of MOSFET
no channel, VGS>VT
This transconductance relates the output current to the input voltage representing the gain of the ____________. The slope of the transconductance curve at any point along it is therefore given as: ____________ for a constant value of VDS.
N-channel E-MOSFET I-V Characteristics
transistor, gm = ID/VGS
When VGS>VTN, a ________ is induced and application of positive VDS cause ____________ to flow.
N-Channel E-MOSFET Construction (Basic Operation)
channel, drain current
Now if you keep VGS fixed and VDS is increased, the drain terminal becomes more positive than ________. The charge carriers get attracted towards drain rather getting accumulated near SiO2 surface and hence the charge density in the channel towards drain decreases. Therefore, increase in “VDS” will ____________ the induced channel towards drain but the “high potential” at drain attract increased number of charge carriers to flow through ______________.
N-Channel E-MOSFET Construction (Basic Operation)
gate, narrow down, narrow channel
with further increase in VDS, the drain current will eventually reach to a ________________ that occurs due to ________ process depicted by the narrower channel.
N-Channel E-MOSFET Construction (Basic Operation)
saturation level, pinch-off
Increase in VGS will cause the pinch-off to occur at higher value of ____ than the earlier.
N-Channel E-MOSFET Construction (Basic Operation)
VDS
Thus higher the VGS, higher is the current flow and higher is the value of VDS that cause ________________ condition.
N-Channel E-MOSFET Construction (Basic Operation)
pinch-off or saturation
The saturation value of VDS is given by _____________
N-Channel E-MOSFET Construction (Basic Operation)
VDsat = VGS - VT
If VGS < VT, the drain current ID = ____ and the MOSFET is said to be in __________
N-Channel E-MOSFET Construction (Basic Operation)
ID=0, cutoff region
for VGS > VT and VDS <= VGS-VT, the MOSFET operate in _______________ or _______________
N-Channel E-MOSFET Construction (Basic Operation)
non-saturation or triode region
for VGS >VT and VDS >= VGS-VT, the MOSFET operate in __________ or _______________
N-Channel E-MOSFET Construction (Basic Operation)
saturation, pinch-off region
when VGS > VTN and for a small values of VDS, a complete ________ from ________ to ________ is __________
N-Channel E-MOSFET Construction (Drain Characteristics Curve)
channel, drain to source, induced
____________ acts as a resistor whose value is determined by VGS
N-Channel E-MOSFET Construction (Drain Characteristics Curve)
E-MOSFET
when VGS > VTN and VDS is larger value but VDS < _________
N-Channel E-MOSFET Construction (Drain Characteristics Curve)
VDS(sat)
the _______________charge density near the drain _____________ and hence the incremental conductance of the channel at the drain ____________,
N-Channel E-MOSFET Construction (Drain Characteristics Curve)
induced inversion, decreases, decreases
when VGS > VTN and VDS = VDS(sat) , the ____________charge density at the drain terminal is _______ hence the incremental channel conductance at the drain is zero
N-Channel E-MOSFET Construction (Drain Characteristics), po
induced inversion, zero
_____________ is at drain
N-Channel E-MOSFET Construction (Drain Characteristics)
Pinch-off point
when VGS >VTN and VDS > VDS(sat), the ________ in the channel at which the inversion charge is zero moves toward the ____________
N-Channel E-MOSFET Construction (Drain Characteristics)
point, source terminal
The ________________________ is similar to the n-channel except that the voltage polarities and current directions are reversed.
p-channel Enhancement-type MOSFET
p-channel Enhancement-type MOSFET
The ___________ operate in pinch-off/saturation region
N-Channel E-MOSFET Construction (Drain Characteristics)
MOSFET
An essential step in the design of a MOSFET amplifier circuit is the establishment of an appropriate __________________.
Biasing Circuits used for MOSFET
dc operating point
Biasing circuit ensures operation of MOSFET in the ______________ for all expected input-signal levels.
Biasing Circuits used for MOSFET
saturation region
The operating point of the MOSFET is located at the coordinate (VDS, ID) on the ___________________.
Biasing Circuits used for MOSFET
characteristic graph
A popular biasing arrangement for enhancement-type MOSFETS
Feedback Biasing
Here the large feedback resistance ___ forces the _________ at the gate to be equal to that at the drain (because IG = 0 ). Since IG = 0mA and VRG=0 V, the dc equivalent network appears as shown
Feedback Biasing
RG, dc voltage
A direct connection now exists between _______ and ______
Feedback Biasing
drain and gate
Another popular biasing arrangement for enhancement-type MOSFETS
Voltage Divider Biasing
It is the ratio of change in the drain source voltage (Δ VDS ) to the change in drain current (ΔlD) at constant gate-source voltage.
Parameters of E-MOSFET
AC drain resistance (rd)
It is the ratio of change in drain current (ΔlD) to the change in gate source voltage (ΔVGS).
Parameters of E-MOSFET
Transconductance parameter (gm)
It is the ratio of change in drain-source voltage (ΔVDS) to the change in gate-source voltage (ΔVGS) .
Parameters of E-MOSFET
Amplification Factor (µ)
The __________ behaves as a voltage- controlled current source.
AC equivalent circuit of n channel E-MOSFET
MOSFET
It provides a drain current proportional to vgs.
AC equivalent circuit of n channel E-MOSFET
E MOSFET
The input resistance is very high ideally infinite.
AC equivalent circuit of n channel E-MOSFET
E-MOSFET
The output resistance is also high
AC equivalent circuit of n channel E-MOSFET
E-MOSFET
Since rd is __________, it can be neglected from the ckt
AC equivalent circuit of n channel E-MOSFET
very high
In the ______________, the MOSFET acts as a voltage-controlled current source: Changes in the ___________ voltage VGS causes changes in the _______ current ID.
E-MOSFET as an Amplifier
saturation region, gate-to-source, drain
Thus the saturated MOSFET behaves as ________________ amplifier
E-MOSFET as an Amplifier
trans-conductance
changes in vi causes changes in ID which in turn changes ____.
E-MOSFET as an Amplifier
Vo
Thus, the trans-conductance amplifier is converted into a __________ amplifier.
E-MOSFET as an Amplifier
voltage
Load line equation:
Large signal Transfer Characteristic of MOSFET Circuit
Vo = VDS = VDD - (RD)(ID)
for vi < VTH the ____________ will be cut off, ID will be ______, and VO = VDS = VDD (point A).
Large signal Transfer Characteristic of MOSFET Circuit
transistor, zero
As Vi exceeds VTH the transistor turns ____, ID ________, and VO __________. This corresponds to points along the segment of the load line from A to В.
Large signal Transfer Characteristic of MOSFET Circuit
on, increases, decreases
_________________ operation continues until VO decreases below VDSsat
Large signal Transfer Characteristic of MOSFET Circuit
Saturation-region
When VDS < VDSsat the MOSFET enters its ______________
Large signal Transfer Characteristic of MOSFET Circuit
triode region
For Vi > VIB, the transistor is driven deeper into the triode region and voltage decreases slowly towards ______.
Large signal Transfer Characteristic of MOSFET Circuit
zero
When the MOSFET is used as a _________, it is operated at the extreme points of the _____________.
MOSFET as a Switch
switch, transfer curve
The device is ____________ by keeping, V < VTH which provide VO = VDD
MOSFET as a Switch
turned off
The switch is turned on by applying a voltage close to _____. Here, vo is ____________.
MOSFET as a Switch
VDD, very small
For the FET to operate as a ______________, the transistor must be biased in the ___________ region, and the instantaneous drain current ID and drain-to-source voltage VDS must be confined to the ___________ region.
E-MOSFET Common Source Amplifier
linear amplifier, saturation, saturation
The device is biased at a somewhere near to the middle of the curve. The voltage signal to be amplified vi is then ________________ on the dc bias voltage.
E-MOSFET Common Source Amplifier
superimposed
