OP-AMP AND ITS APPLICATIONS | NCERTBOOKSPDF.COM

Short notes

Objective questions (Answers are given below)

An OP-AMP can be classified as …………. amplifier.
(a) linear
(b) low-rin
(c) positive feedback
(d) RC-coupled.
An ideal OP-AMP has
(a) infinite Aν
(b) infinite Ri
(c) zero R0
(d) all the above.
OP-AMP have become very popular in industry
mainly because
(a) they are dirt cheap
(b) their external characteristics can be
changed to suit any application
(c) of their extremely small size
(d) they are available in different packages.
Since input resistance of an ideal OP-AMP is
infinte
(a) its output resistance is zero
(b) its output voltage becomes independent of
load resistance
(c) its input current is zero
(d) it becomes a current-controlled device.
The gain of an actual OP-AMP is around
(a) 1,000,000 (b) 1000
(c) 100 (d) 10,000
When an input voltage of 1 V is applied to an
OP-AMP having Aν = 106 and bias supply of +
15 V, the output voltage available is
(a) 15 × 106 V (b) 106
V
(c) 15 μV (d) 15 V.

An inverting amplifier has Rf = 2 M and R1 = 2
K, Its scale factor is
(a) 1000 (b) −1000
(c) 10 −3 (d) −10−3
In an inverting amplifier, the two input terminals
of an ideal OP-AMP are at the same potential
because
(a) the two input terminals are directly shorted
internally
(b) the input impedance of the OP-AMP is infinity
(c) common-mode rejection ratio is infinity
(d) the open-loop gain of the OP-AMP is infinity.
The open-loop gain of an operational amplifier
is 105. An input signal of 1 mV is applied to
the inverting input with the non-inverting input
connected to the ground. The supply voltages
are ±10 V. The output of the amplifier
will be
(a) + 100 V
(b) − 100 V
(c) + 10 V (approximately)
(d) − 10 V (approximately)

The output voltage of the circuit shown in Fig.
68.42 is
Fig. 68.42
(a) 1·0 V (b) 1·5 V
(c) 2·0 V (d) 2·5 V
In the circuit shown in Fig. 68.43, the value of
output, ν0 is
(a) + 3 V (b) − 3 V
(c) − 7 V (d) + 7 V
Fig. 68.43
When in a negative scaler, both R1 and Rf are
reduced to zero, the circuit functions as
(a) integrator (b) subtractor
(c) comparator (d) unity follower.
The two input terminals of an OP-AMP are
known as
(a) positive and negative
(b) differential and non-differential
(c) inverting and non-inverting
(d) high and low.
The purpose of comparator is to
(a) amplify an input voltage
(b) detect the occurrence of a changing input
voltage
(c) maintain a constant output when the dc
input voltage changes.
(d) produce a change in input voltage when
an input voltage equals the reference voltage.
The OP-AMP comparator circuit uses
(a) positive feedback
(b) negative beedback
(c) regenerative feedback
(d) no feedback
The feedback path in an OP-AMP integrator
consists of
(a) a resistor
(b) a capacitor
(c) a resistor and a capacitor in series
(d) a resistor and a capacitor in parallel.
The feedback path in an OP-AMP differentiator
consists of
(a) a resistor
(b) a capacitor
(c) a resistor and a capacitor in series
(d) a resistor and a capacitor in parallel