ELG4135: Assignment 1
Based on Sedra 5th Edition
D2.12: Design an inverting op-amp circuit for which the gain is -5 V/V and the total
resistance used is 120 kΩ.
Solution:
100 kΩ
20 kΩ
vi
vo
+
vo
R
= −5 = − 2 ; R 2 = 5R1
vi
R1
R1 + R 2 = 120 kΩ
5R1 + R1 = 120 kΩ
R1 = 20 kΩ and R 2 = 100 kΩ
D2.14 Using the following circuit and assuming an ideal op amp, design an inverting
amplifier with a gain of 26 dB having the largest possible input resistance under the
constraint of having to use resistors no larger than 10 MΩ. What is the input resistance of
your design?
R2
R1
vi
+
vo
D2.20. (a) Design an inverting amplifier with a closed-loop gain of -100 V/V and an
input resistance of 1 kΩ.
(b) If the op amp is known to have an open-loop gain of 1000 V/V, what do you expect
the closed loop gain of your circuit to be?
( c ) Give the value of a resistor you can place in parallel (shunt) with R1 to restore the
closed loop gain to its nominal value.
D2.29. An inverting op amp circuit using an ideal op amp must be designed to have a
gain of -1000 V/V using resistors no larger than 100 kΩ.
(a) For the simple two resistor circuit, what input resistance would result?
(b) If a T-network is used as feedback circuit for the inverting amplifier with three
resistors of maximum value, what input resistance results? What is the value of
the smallest resistor needed?
D2.46 in Sedra 4th edition or D2.51 5th edition.
D2.67. Design a difference amplifier to realize a differential gain of 100, a differential
input resistance of 20 kΩ, and a minimum CMRR of 80 dB. Assume the op amp ideal.
D2.64 in Sedra 4th edition or D2.76 in Sedra 5th edition.
2.85 in Sedra 4th edition or 2.100 in Sedra 5th edition.
D2.88 in Sedra 4th edition or D2.103 in Sedra 5th edition.
D2.91 in Sedra 4th edition or D2.106 in Sedra 5th edition.
D2.119. Consider a low pass active filter. Derive its transfer function, its DC gain and the
30dB frequency. Design the circuit to obtain an input resistance of 1 kΩ, a DC gain of 20
dB, and a 3-dB frequency of 4 kHz. At what frequency does the magnitude of the transfer
function reduce to unity?
2.121. A differentiator utilizes an ideal op amp, a 10 kΩ resistor and 0.01 µF capacitor.
What is the frequency fo at which its input and output sine-wave signals have equal
magnitude? What is the output signal for a 1-V peak to peak sine-wave input with
frequency equal to 10 fo?