IC MOSFET AMPLIFIERS
1. Define an Integrated circuit.
An
integrated circuit(IC) is a miniature ,low cost electronic circuit consisting
of active and passive components fabricated together on a single crystal of
silicon.The active components are transistors and diodes and passive components
are resistors and capacitors.
2. What are the advantages of ICs over discrete
circuits.?
1. Minimization
& hence increased equipment density.
2. Cost
reduction due to batch processing.
3. Increased
system reliability
4. Improved
functional performance.
5. Matched
devices.
6. Increased
operating speeds
7. Reduction
in power consumption
3. List the disadvantages of ICs
• Inductors
cannot be fabricated
• IC
function at very low voltage
• Limited
amount of power
• Excessive
heat
4. Define steering current.
In
integrated circuit designs circuits use constant sources.here the constant d.c
current called reference current is generated at one location and is then
replicated at various other locations for biasing the various stages of
amplifier present in the circuit. this process is known as current steering.
5. State the advantages of current steering?
• The
external components such as precision resistors required to generate a
predictable and stable reference current,need not be repeated for every
amplifier stage.
• The bias
currents of the various stages track each other when there is any change due to
power supply voltage or temperature.
6. Define cascade current mirror circuit.
MOSFET
current source circuits the output resistance is a measure of stability of Io
with respect to the changes in the output voltage. Here MOSFET T3 andT4 are
included to provide higher output resistance. This circuit is known as cascade
current mirror circuit.
7. Define Wilson current mirror circuit?
MOSFET
Wilson current source the VDS values of T1 and T2 are not equal. Since λ is not
zero, the ratio Io/Iref is slightly different from the aspect ratio.
8. State the advantages of Wilson current mirror
circuit.
The
advantages of these circuits are the increase in output resistance and hence
increase the stability of output current.
9. List the various types of active loads?
There are
three types of load devices:
• N-channel
enhancement mode device
• N-channel
depletion-mode device
• P-channel
enhancement mode device
10.
State the
advantages of NMOS amplifier with depletion load over enhancement load.
The
voltage gain of NMOS amplifier with depletion load is significantly larger than
that
with the
enhancement load, however, like NMOS amplifier with enhancement load, the body
effect lowers the small-signal voltage gain.
11.
Define β
and α.
• α is a
current gain which is the ratio of collector current to the base current.
• β is a
forward current gain which is the ratio of collector current to the emitter
current.
12.
What is
meant by over drive factor?
The over
drive factor is defined as the ratio of IB and IBS.
Where, IB is the base current and IBS is the base current
that produces the saturation.
13. Define delay time.
During
the delay time period, base emitter voltage VBE is applied, the base
current IB rises to IBS and the collector current IC
is equal to zero or collector emitter leakage current ICEO. The time
required to charge the base emitter capacitance to, VBES=0.7 V.
14. Define rise time.
During
the rise time period, collector current IC raises to steady state
values ICS and the collector emitter voltage falls from VCC
to VCES the rise time depends on the input capacitance.
15.
What is
the need of driver circuit?
9 It provides amplified voltage and current to the device.
9 It provides isolation between control circuit and power circuit.
16.
State
methods which are used to provide effect of increased RE.
• Constant
current bias method
• Use of
current mirror circuit
• Use of an
active load.
17.
What is
current mirror ?
The
circuit in which the output current is forced to equal the input current is
called as current mirror circuit. In a current mirror circuit, the output
current is the mirror image of input current.
18.
State
advantages of current mirror circuit. 1)Provides very high emitter resistance RE. 2)Easy to
fabricate.
3)Requires
less components then constants current bias. 4)Simple to design
5)With
properly matched transistors,collector current thermal stability is achieved.
19.
What are
the types of internal capacitance in the MOSFET?
There two
types of
1.Gate
capacitance
2.junction
capacitance
20.Define gate capacitance.
It is a
parallel plate capacitance formed by a gate electrode with the channel with the
oxide layer acts as a capacitor dielectric. It is denoted as Cox.
21.
List the
advantage of active load.
• provides
very high ac resistance
• provides
high differential mode voltage gain
• Ad High
• CMRR High
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