Applications of Op Amp
1.What is the need for an instrumentation
number of industrial and consumer applications, the measurement of physical
quantities is usually done with the help of transducers. The output of
transducer has to be amplified So that it can drive the indicator or display
system. This function is performed by an instrumentation amplifier.
2.List the features of instrumentation amplifier:
high gain accuracy
high gain stability with low temperature co-efficient
low dc offset
low output impedance
3.What is a comparator?
comparator is a circuit which compares a signal voltage applied at one input of
an op-amp with a known reference voltage at the other input. It is an open loop
op - amp with output + Vsat .
4.What are the applications of comparator?
Zero crossing detector
Time marker generator
5.What is a Schmitt trigger?
trigger is a regenerative comparator. It converts sinusoidal input into a
square wave output. The output of Schmitt trigger swings between upper and
lower threshold voltages, which are the reference voltages of the input
6.What is a multivibrator?
are a group of regenerative circuits that are used extensively in timing
applications. It is a wave shaping circuit which gives symmetric or asymmetric
square output. It has two states either stable or quasi- stable depending on
the type of multivibrator.
7.What do you mean by monostable multivibrator?
is one which
generates a single
pulse of specified duration in
response to each external trigger signal.
It has only one stable state.
Application of a trigger causes a change to the quasi-stable state.An
signal generated due to charging and discharging of the capacitor produces the
transition to the original stable state.
8.What is an astable multivibrator?
multivibrator is a free running oscillator having two quasi-stable states.
Thus, there is oscillations between these two states and no external s i g n a
l a r e required to produce the change in state.
9.What is a bistable multivibrator?
multivibrator is one that maintains a given output voltage level unless an
external trigger is applied . Application of an external trigger signal causes
a change of state, and this output level is maintained indefinitely until an
second trigger is applied . Thus, it requires two external triggers before it
returns to its initial state
10.What are the requirements for producing
sustained oscillations in feedback circuits?
The total phase shift around the loop must be zero
at the desired frequency of oscillation, fo. ie, LAB =0 (or) 360°
At fo, the magnitude of the loop gain | A b |
should be equal to unity
11.What are the different types of filters?
functions: Low pass filter,High
pass filter,Band pass filter, Band
order of transfer function: first ,second,third higher order filters.
12.List the broad classification of ADCs.
Direct type ADC.
Integrating type ADC.
13.List out the direct type ADCs.
Flash (comparator) type converter
Counter type converter
Tracking or servo converter
Successive approximation type converter
some integrating type converters.
Charge balancing ADC
Dual slope ADC
15.What is integrating type converter?
converter that perform conversion in an indirect manner by first changing the
analog I/P signal to a linear function of time or frequency and then to a
digital code is known as integrating type A/D converter.
16.Explain in brief the principle of operation of
successive Approximation ADC.
circuit of successive approximation ADC consists of a successive approximation
register (SAR), to find the required value of each bit by trial &
error.With the arrival of START command, SAR sets the MSB bit to 1. The O/P is
converted into an analog signal & it is compared with I/P signal. This O/P
is low or High. This process continues until all bits are checked.
17.What are the main advantages of integrating type
The integrating type of ADC’s do not need a
sample/Hold circuit at the input.
It is possible to transmit frequency even in noisy
environment or in an isolated form.
18.Define conversion time.
defined as the total time required to convert an analog signal into its digital
output. It depends on the conversion technique used & the propagation delay
of circuit components.
conversion time of a successive approximation type ADC is given by T(n+1)
time n----no. of bits
19.Define resolution of a data converter.
resolution of a converter is the smallest change in voltage which may be
produced at the output or input of the converter.
(in volts)= VFS/2n-1=1 LSB increment. The resolution of an ADC is
defined as the smallest change in analog input for a one-bit change at the
20.Explain in brief stability of a converter:
of converter changes with temperature age & power supply variation. So all
the relevant parameters such as offset, gain, linearity error &
monotonicity must be specified over the full temperature & power supply
ranges to have better stability performances.
21.What is meant by linearity?
linearity of an ADC/DAC is an important measure of its accuracy & tells us
how close the converter output is to its ideal transfer characteristics. The
linearity error is usually expressed as a fraction of LSB increment or
percentage of full-scale voltage. A good converter exhibits a linearity error
of less than ±½LSB.
22.What is a sample and hold circuit? Where it is
and hold circuit is one which samples an input signal and holds on to its last
sampled value until the input is sampled again. This circuit is mainly used in
digital interfacing, analog to digital systems, and pulse code modulation
23.Define sample period and hold period.
during which the voltage across the capacitor in sample and hold circuit is
equal to the input voltage is called sample period.The time period during which
the voltage across the capacitor is held constant is called hold period.