EKT 214 ANALOG ELECTRONIC CIRCUIT II
SEM II 2012/2013
TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY
RESPONSE
QUESTION
1.
Describe briefly the following terms as applied to an ideal operational amplifier:
i)
iii)
v)
vii)
2.
Virtual ground;
Input dc offset voltage;
Input bias current;
Slew rate.
ii)
iv)
vi)
Virtual short;
Output dc offset voltage;
Input offset current;
List down five parameters of an op-amp and give comparisons between an ideal and a practical opamp with regards to these parameters and hence draw the equivalent circuit of an ideal op-amp and
a simplified equivalent circuit of a practical op-amp.
3.
With the aid of suitable diagrams, give brief description of the terms DIFFERENTIAL MODE
INPUT and COMMON-MODE INPUT as applied to an op-amp and hence give the mathematical
definition for the term COMMON-MODE REJECTION RATIO (CMRR).
4.
Consider an operational amplifier with ideal parameters and the op-amp is operated as an inverting
constant gain multiplier with the input signal voltage V1 applied through R1 and the output signal
Vo is fed back to the input through RF.
a)
Draw the circuit diagram.
b)
Draw the ac equivalent circuit for practical op-amp, ideal op-amp and redrawn the equivalent
circuit.
c)
Prove that the gain is controlled by 𝑅𝐹 & 𝑅1 using superposition theorem and appropriate
equivalent circuit.
1
EKT 214 ANALOG ELECTRONIC CIRCUIT II
SEM II 2012/2013
TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY
RESPONSE
5.
Consider an operational amplifier in Figure 1 with ideal parameters and the op-amp is operated as
non-inverting constant gain multiplier.
b)
Draw the ac equivalent circuit.
c)
Prove that the gain is A  1 
RF
using voltage divider rule.
R1
Figure 1
6.
Perform an ac analysis on the circuit in Figure 2 to obtain an expression for the voltage gain Av
where;
Av 
vO
vI
2 Figure 2
EKT 214 ANALOG ELECTRONIC CIRCUIT II
SEM II 2012/2013
TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY
RESPONSE
7.
The inverting amplifier in Figure 3 receives an input signal from the source vs. The source is
capable of delivering a maximum current of 4 A at a peak voltage of 0.2 V. Design the amplifier
for a gain |Av| of 20. Assume that the op-amp is ideal.
Figure 3
8.
Calculate the output voltage V2 & V3 based from Figure 4.
Figure 4
3
EKT 214 ANALOG ELECTRONIC CIRCUIT II
SEM II 2012/2013
TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY
RESPONSE
9.
Determine the output voltage of the DAC in Figure 5(a). The sequence of 4 digit binary
codes represented by the waveforms in Figure 5(b) are applied to the inputs. A high level
is a binary 1, and a low level is a binary 0. The least significant binary digit is D0. Draw a
graph of binary input versus Vout.
Figure 5
10. Based from Figure 6, find the output voltage, Vout and illustrate the respective equivalent
circuit when the binary input is 0001.
Figure 6
4
EKT 214 ANALOG ELECTRONIC CIRCUIT II
SEM II 2012/2013
TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY
RESPONSE
11.
For the circuit in Figure 7;
a)
derive the expression for the output voltage vO in terms of the input voltages vI1 and vI2, and
the circuit parameters R1, R2, R3, and R4;
b)
Show that under certain condition, the output voltage vO is proportional to the difference of
the input voltages vI1 and vI2 and determine the constant of proportionality under this
condition.
R2
vI1
R1
vO
R3
vI2
+
R4
Figure 7
12.
Design the circuit in Figure 8(a) to produce an output voltage vO in Figure 8(c) when the input
voltage vI is as shown in Figure 8(b). Assume the op-amp is ideal and use C = 220 pF.
Figure 8(a)
5
EKT 214 ANALOG ELECTRONIC CIRCUIT II
SEM II 2012/2013
TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY
RESPONSE
Figure 8(b)
Figure 8(c)
13.
For the circuit in Figure 9(a), C = 0.1 F and R = 10 k. Both the output and input voltages are
zero at t = 0. An input voltage vI shown in Figure 9(b) is applied to the circuit. Sketch the
resulting output waveform vO(t).
Figure 9(a)
6
EKT 214 ANALOG ELECTRONIC CIRCUIT II
SEM II 2012/2013
TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY
RESPONSE
Figure 9(b)
14.
The input signal in Figure 10(a) is applied to the comparator in Figure 10(b). Draw the output
showing its proper relationship to the input signal. Assume the maximum output levels of the
comparator are ±14𝑉.
Figure 10
7
EKT 214 ANALOG ELECTRONIC CIRCUIT II
SEM II 2012/2013
TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY
RESPONSE
15.
Determine the output voltage waveform for Figure 11. (Hint: Find the values of upper
trigger point (UTP) and the lower trigger point (LTP)).
Figure 11
8