Download Ans: Analogue Electronics

Analogue Electronics
C.I.T
Q1: What is analog electronics?
Ans: Analogue Electronics:
Analogue electronics are electronic systems with
systems with a continuously variable signal in contrast to digital electronics
where signals usually take only two different levels. The term “analogue”
describes the proportional relationship between a signal and a voltage or
current that represents the signal. The word analogue is derived from the
Greek word (analogos) meaning “proportional”.
Q2: What are discrete component?
Ans: Discrete Component:
A discrete device (or discrete component) is an
electronic component with just one circuit element either passive (resistor,
capacitor, inductor) or active (transistor or vacuum tube), other than an
integrated circuit. Several discrete devices are combined to from a discrete
circuit. Such discrete circuits are different from integrated circuits and hybrid
circuits, which are built from several circuit elements in one package. Analogue
electronics have passive discrete components which are: resistors, capacitor,
inductor, etc.
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Analogue Electronics
C.I.T
Q3: What is resistor?
Ans: Resistor:
A resistor is a two-terminal electronic component that produces
a voltage across its terminals that is proportional to the electric current passing
through it in accordance with ohm’s law:
V=IR
Q4: What is capacitor?
Ans: Capacitor:
A capacitor (formerly known as condenser) is a passive
electronic component consisting of a pair of conductors separated by a
dielectric (insulator).
Q5: What is inductor?
Ans: Inductor:
An inductor or a reactor is a passive electrical component that
can store energy in a magnetic field created by the electric current passing
through it.
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Analogue Electronics
C.I.T
Q6: What is common emitter amplifier?
Ans: Common Emitter Amplifier:
A BJT circuit in which the emitter connection
is common to both input and output.
Q7: What is a fixed bias in transistor?
Ans: Fixed Bias in Transistor:
It’s the alternative to self biased. Typically a
resistor voltage divider sets the base to ground voltage on (for instance) a BJT.
Self biased does not have this divider and thus transistor or FET is biased not
on any hard criterion such as a resistive divider but on its own characteristics.
Q8: What is the usage of fixed bias?
Ans: Usage of Fixed Bias:
Usage: the feedback also increases the input
impedance of the amplifier when seen from the base, which can be
advantageous. Due to the above disadvantages, this type of biasing circuit is
used only with careful consideration of the trade-offs involved.
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Analogue Electronics
C.I.T
Q9: What is the difference between fixed bias circuit and self bias circuit?
Ans: Fixed Bias Circuit:
Fixed bias circuits get their bias voltages from
independently designed reference voltage sources (or even something as
simple as a voltage divider). Often is the case that the bias may be left for the
end-user to give some control over the operation point of the circuit.
Self Bias Circuit:
Self biased circuits get their bias voltages from the
circuit itself, often in the form of a negative feedback. This is very useful when
a circuit is extremely sensitive to bias points and it becomes impractical to
provide external biases that are correct to very high accuracies. This can
happen in high gain amplifiers with very high impedance output nodes, such as
a common source amplifier with an active load. The operation of the circuit
depends on the bias of the active load. It would therefore be desirable to
sacrifice some of this gain providing a negative feedback from the output to
the gate of the active load. This way, you won’t have to bias the circuit
yourself, but will lose some of the gain of the circuit as a price.
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Analogue Electronics
C.I.T
Q10: What is cathode bias?
Ans: Cathode Bias:
Cathode bias amps, which we do not manufacture use a
capacitor to make the grid more negative and do not usually require any
adjustment. The downside is they usually have more distortion which make
them sound a little more colored. TT amps feature fixed bias which requires
tube adjustment but results in more accurate bias points and less distortion.
Q11: What is a VDB (Voltage Divider Bias)?
Ans: Voltage Divider Bias (VDB):
Biasing method used with amplifiers in which
two series resistors connected across a source. The junction of the two biasing
resistors provides correct bias voltage for the amplifier.
Q12: What is the working of Voltage Divider Bias?
Ans: Working of Voltage Divider Bias:
Two words divider and bias. A divider is
usually used to get a bias voltage.
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Analogue Electronics
C.I.T
Q13: Why Voltage Divider Bias is also called Self Bias?
Ans: Voltage Divider Bias is called Self Bias:
A grid bias provided automatically
by the resistor in the cathode or grid circuit of an electron tube; the resulting
voltage drop across the resistor servers as the grid bias. Also known as
automatic C bias; automatic grid bias. This arrangement is called SELF-BIAS.
Now, if an increase of temperature causes an increase in collector current, the
collector voltage (VC) will fall because of the increase of voltage produced
across the load resistor (RL). One of the most widely used combination-bias
systems is the voltage-divider type.
Q14: Why Common Emitter Configuration of amplifier is commonly used?
Ans: Use of Common Emitter Configuration of Amplifier:
Because amplification factor
beta is usually ranges from 20-500 hence this configuration gives appreciable
current gain as well as voltage gain at its output.
On the other hand in the
Common Collector Configuration has very high input resistance (~750K Ω) &
very low output resistance (~25Ω) so the voltage gain is always less than one
and its most important application is for impedance matching for driving from
low impedance load to high impedance source.
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Analogue Electronics
C.I.T
Q15: What is Common Collector Amplifier?
Ans: Common Collector Amplifier:
A BJT circuit in which the collector
connection is common to both input and output.
Q16: What is a Common Collector Configuration is called Emitter Follower?
Ans: Common Collector Configuration is called Emitter Follower:
Because of
the geometry of the Common Collector Configuration, changes in base voltage
appear at the emitter. Said another way, what happens at the base pretty
much happens at the emitter, and the emitter can be said to “mirror” or
“follow” the base .the emitter is a follower of the base, and the name Emitter
Follower appeared and was used.
Q17: What are the applications of the common collector amplifier?
Ans: Applications of Common Collector Amplifier:
The low output impedance
allows a source with a large output impedance to drive small load impedance;
it functions as a voltage buffer. In other words, the circuit has current gain
(which depends largely on the HFE of the transistor) instead of voltage gain. A
small change to input current results in much larger change in the output
current supplied to the output load. Other applications are: high input
impedance, low output impedance, non-inverting, approximately unity gain.
Output buffers/line drivers and similar.
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Analogue Electronics
C.I.T
Q18: The output voltage of an Emitter Follower is?
Ans: Output Voltage of an Emitter Follower:
The output voltage of an Emitter
Follower is the same as the base minus VBE drop and it is used for more power
transfer.
Q19: Where the Common Collector Configuration is commonly used?
Ans: Use of Common Collector Configuration:
This configuration is commonly
used in the output stages of class-B and class-AB amplifier – the base circuit is
modified to operate the transistor in class-B or AB mode. In class-A mode,
sometimes an active current source is used instead of RE to improve linearity
and/or efficiency.
Q20: What is frequency response?
Ans: Frequency Response:
Frequency response is a measure of a system’s
output spectrum in response to an input signal. In audio it is used in
connection with amplifiers, loudspeakers and microphones.
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Analogue Electronics
C.I.T
Q21: What is the low frequency response of Common Emitter Amplifier?
Ans: Low Frequency of Common Emitter Amplifier:
A simple CE amplifier it has
a decoupling capacitor in the input stage to remove DC components so the LF
response will be quite poor. Other RC component needs to be added to the
circuit to flatten the frequency response.
Q22: How can we calculate the frequency response of C1, C2, and C3 in the
above configuration?
Ans: Calculate the Frequency response of C1, C2, and C3:
We can calculate the
frequency response with the help of following formulas in the above
configuration:
1. f1=
1
Frequency response due to C1
2𝜋𝐶1(𝑅𝑖𝑛+𝑅𝐺)
1
2. f2=
𝑅1||𝑅2||𝑅0
2𝜋𝐶2(
+𝑅𝑒1+𝑟′𝑒)||𝑅𝑒2
𝛽𝑎𝑐
3. f1=
1
2𝜋𝐶3(𝑅0+𝑅1)
Frequency response due to C2
Frequency response due to C3
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Analogue Electronics
C.I.T
Q23: What is oscilloscope?
Ans: Oscilloscope:
An electronic measuring instrument that creates a visible
two-dimensional graph, on a screen, of one or more continuously varying
voltages or currents.
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