1

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A SUMMER TRAINING REPORT
On
ANALOG SIGNAL PROCESSING
Submitted by:
Kavya Gupta
Roll No. 01596402813
In partial fulfilment of Summer Training for the award of the degree
Of
BACHELOR OF TECHNOLOGY
In
ELECTRONICS AND COMMUNICATION ENGINEERING
Maharaja Agrasen Institute of Technology
Rohini -sector 22, Delhi
Guru Gobind Singh Indraprastha University, Delhi
2013-2017

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ACKNOWLEDGEMENT
The Training opportunity I had with ‘RADIENCE EDUTECH’ was a great chance for
learning and professional development. Therefore, I consider myself as a very lucky
individual as I was provided with an opportunity to be a part of it. I am also grateful for
having a chance to work with a group of students from different colleges during my
Training.
I am using this opportunity to express my deepest gratitude and special thanks to
“Dr K. L. Pushker (Assistant Professor)” who in spite of being extraordinarily busy
with his duties, took time out to hear, guide and keep me on the correct path. For their
careful and precious guidance which were extremely valuable for my study both
theoretically and practically, I am very great full.

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Abstract
It is now fairly well understood by academicians as well as practice engineers and
circuit designers that in spite of the dominance of digital circuits and systems and
digital signal processing, the importance of analog circuits and analog signal
processing has not diminished by any account.
In fact, in several areas and applications, analog circuits are indispensible e. g.
continuous time filters, amplifiers, precision rectifiers, analog-to-digital (A/D)
converters, digital-to-analog (D/A) converters and certain classes of communication
circuits and artificial neural networks.
In view of the above, research on analog circuit design has continued to remain
prominent although, the design considerations and focus have changed from time to
time alongside the changes in integrated circuit (IC) technology.

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CONTENTS
CERTIFICATE…………………………………………………………… 2
ACKNOWELEDGMENT………………………………………………... 3
ABSTRACT………………………………………………………………. 4
LIST OF FIGURES………………………………………………………. 5
1. Introduction………………………………………………………………. 7
2. Operational Amplifier……………………………………………………. 8
3. Operational Tranconductance Amplifier………………………………...
(OTA)
10
4. Current Conveyors………………………………………………………..
(CC)
13
5. Current Feedback Operational Amplifier…………………………………
(CFOA)
16
6. Oscillators…………………………………………………………………
 Pspice Simulations
18
7. Filters……………………………………………………………………...
 Pspice Simulations
37
8. AM Modulator using OTA……………………………………………….. 39
9. Translinear Circuits……………………………………………………… 41
10. References………………………………………………………………... 63

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LIST OF FIGURES
1. Symbolic Notation of opamp …………………………………………… 8
2. Opamp as Vccs ………………………………………………...……….. 8
3. Symbolic Notation of ota ……………………………………………….. 10
4. CA3080(OTA) ………………………………………………………….. 11
5. Symbolic notation of CCI ………………………………………………. 13
6. Symbolic notation of CCII ……………………………………………… 14
7. Symbolic notation of CCIII ………………………………..................... 15
8. Symbolic notation of CFOA …………………………………………….. 16
9. Phase shift oscillator using opamp ……………………………………… 19
10. Hartley oscillator using opamp …………………………………………. 22
11. Colpitts oscillator using opamp ……………………………………....... 25
12. Weinn Bridge oscillator using opamp…………………………………….
…………………………………………..
28
13. Weinn Bridge oscillator using ota………………………………………... 31
14. Oscillator using CFOA ……………………………….............................. 34
15. Implementation of Passive All-pass filter………………………………… 40
16. Implementation of Passive Low-pass filter………………………………. 41
17. Implementation of Passive High-pass filter……………………………… 42
18. Implementation of Passive Band-pass filter……………………………… 43
19. Lpf(2nd order) using opamp………………………………………………..
…………………
44
20. Hpf(2nd order) using opamp………………………………………………. 45
21. Bpf(2nd order) using opamp……………………………………………….. 47
22. Brf(2nd order) using opamp……………………………………………….. 48
23. Universal Filter -1 using ota……………………………………………… 50
24. Universal Filter -2 using ota………………………………………………
.
53
25. Implementing DSB-AM using ota…………………………………………
.
58
26. Arrangement of transistors in transliner fashion…………………………. 61

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Introduction
Analog signal processing is any type of signal processing conducted on continuous
analog signals by some analog means (as opposed to the discrete Digital Signal
Processing where the signal processing is carried out by a digital process). "Analog"
indicates something that is mathematically represented as a set of continuous values.
This differs from "digital" which uses a series of discrete quantities to represent signal.
Analog values are typically represented as a voltage, electric current or electric charge
around components in the electronic devices. An error or noise affecting such physical
quantities will result in a corresponding error in the signals represented by such physical
quantities.
Examples of analog signal processing include filters in loudspeakers, "bass", "treble"
and "volume" controls on stereos, and "tint" controls on TVs. Common analog
processing elements include capacitors, resistors, inductors and transistors.

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The Ubiquitous Op-amp
AV
V+
V- VO
I+
I-
+
-
+
-
Figure 1: Symbolic Notation Of Opamp
In the world of analog circuits, it is widely believed that almost any function can be
performed using the classical voltage-mode op-amp (VOA). Thus, on one hand, one can
realize using op-amps, all linear circuits such as the four controlled sources (VCVS,
VCCS, CCVS and CCCS), integrators, differentiators, summing and differencing
amplifiers, variable-gain differential/instrumentation amplifiers, filters, oscillators etc.
On the other hand, op-amps can also be used to realize a variety of non-linear functional
circuits such as comparators, Schmitt trigger, sample and hold circuits, precision
rectifiers, multivibrators, log-antilog amplifiers and a variety of relaxation oscillators.
Here are some short comings of Op-amp:
1. Matched Impedances and not minimum number of passive components
Consider this well-known VCCS configuration
Figure 2: Opamp As Vccs

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A straight forward analysis of the circuit shows that the relation
between the output current and input voltage (assuming ideal op-amp) for the
circuit is given by:







142
3
1
1
RRR
R
V
R
V
I o
in
O
From the above, it may be seen that to realize a VCCS the op-amp circuits not
only require more than the minimum number of resistances necessary' but also require
that all the four resistors should have either a relationship R1 = R2R4/R3 or else all the
four resistors be equal-valued and matched so that the output current becomes
independent of the output voltage and depends only on the input voltage, as required.
Thus, any mismatch in resistor values from the intended ones would degrade the
performance of the circuit.
2. The Gain-Bandwidth Conflict
The gain and the bandwidth cannot be set independent of each other i.e. there is a gain-
bandwidth conflict.
3. Slew-Rate Based Limitations
At large input voltages or high frequencies or a combination of the two, the
output voltage fails to respond with the same speed as the input (due to finite
maximum SR) and this results in slew-induced distortion. Conversely, to avoid
slew-induced distortion, the input voltages and their frequencies are constrained to be
kept small. Thus, the finite slew rate affects both the dynamic range of the op-amp
circuits as well as the maximum frequency of the input signal which can be applied
without causing noticeable distortion in the output waveform.

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OPERATIONAL TRANSCONDUCTANCE AMPLIFIER
-
V+
V-
IO
-IO
Ibias
+
gm
+
-
I+
I-
Figure 3: Symbolic Notation Of OTA
The operational transconductance amplifier (OTA) is an amplifier whose differential
input voltage produces an output current. Thus, it is a voltage controlled current source
(VCCS). There is usually an additional input for a current to control the amplifier's
transconductance. The OTA is similar to a standard operational amplifier in that it has a
high impedance differential input stage and that it may be used with negative
feedback.[1]
The first commercially available integrated circuit units were produced by RCA in 1969
(before being acquired by General Electric), in the form of the CA3080 (discontinued
product) , and they have been improved since that time. Although most units are
constructed with bipolar transistors, field effect transistor units are also produced. The
OTA is not as useful by itself in the vast majority of standard op-amp functions as the
ordinary op-amp because its output is a current.[citation needed] One of its principal
uses is in implementing electronically controlled applications such as variable frequency
oscillators and filters and variable gain amplifier stages which are more difficult to
implement with standard op-amps.
The OTA is popular for implementing voltage controlled oscillators (VCO) and filters
(VCF) for analog music synthesizers, because it can act as a two-quadrant multiplier as
we’ll see later. For this application the control input has to have a wide dynamic range of
at least 60 dB, while the OTA should behave sensibly when overdriven from the signal
input (in particular, it should not lock up or phase reverse). Viewed from a slightly

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different angle an OTA can be used to implement an electrically tunable resistor that is
referenced to ground, with extra circuitry floating resistors are possible as well.
The CA3080 [3]
Figure 4: CA3080(OTA)
The CA3080 is probably the most simple standalone bipolar OTA that you can find. It
consists of only the input differential pair and the current mirrors that bias the input
transistors and produce the output current.
In particular, the mirror for the tail current is a simple Widlar type and emitter
degeneration cannot be used as the tail current can vary widely. It is therefore
important to keep the differential and current inputs at the same potential, otherwise
the transconductance gets modulated by the common mode input voltage.
Unfortunately the datasheet does not show the circuit for measuring the CMRR, but it
appears that the common mode amplitude was low for the test and the input potentials
about the same. The output current mirrors are all Wilson type, the pnp mirrors also

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use a Darlington pair for the cascade transistor to get around the low beta of the pnp
transistor in this process.
ADVANTAGES OF OTA
1. Less Passive components count
2. Also full active as well as passive circuits can be made as resistors, inductors and
capacitors all can be simulated using OTA
3. So fully integrated IC components can be made
4. Electronically controllable (tuneable).
NON-IDEAL CHARACTERISTICS
As with the standard op-amp, practical OTA's have some non-ideal characteristics.
These include [4]:
1. Input stage non-linearity at higher differential input voltages due to the characteristics of
the input stage transistors. In the early devices, such as the CA 3080, the input stage
consisted of two bipolar transistors connected in the differential amplifier configuration.
The transfer characteristics of this connection are approximately linear for differential
input voltages of 20 mV or less. This is an important limitation when the OTA is being
used open loop as there is no negative feedback to linearise the output. One scheme to
improve this parameter is mentioned below.
2. Temperature sensitivity of transconductance.
3. Variation of input and output impedance, input bias current and input offset voltage with
the transconductance control current.

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CURRENT CONVEYORS
However when larger circuit design became even difficult with OTA, current conveyors
proposed by Sedra and Smith in 1968 gained a lot of popularity especially since 2000s.
A current conveyor is an abstraction for a three terminal analogue electronic device. It
is a form of electronic amplifier with unity gain. There are three versions of generations
of the idealized device, CCI, CCII and CCIII. When configured with other circuit
elements, real current conveyors can perform many analogue signal processing
functions, in a similar manner to the way op-amps and the ideal concept of the op-amp
are used.
First generation(CCI)
Figure 5: Symbolic Notation of CCI
The CCI is a three-terminal device with the terminals designated X, Y, and Z. The
potential at X equals whatever voltage is applied to Y. Whatever current flows into Y
also flows into X, and is mirrored at Z with a high output impedance, as a variable
constant current source. In sub-type CCI+, current into Y produces current into Z; in
a CCI-, current into Y results in an equivalent current flowing out of Z.[2]
Ideally, the CCI± is characterized by the hybrid matrix:
































Z
X
Y
Z
X
Y
V
I
V
I
V
I
010
001
010

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Secondgeneration(CCII)
Figure 6: Symbolic Notation of CCII
In a more versatile later design, no current flows through terminal Y. The ideal CCII can
be seen as an ideal transistor, with perfected characteristics. No current flows into the
gate or base which is represented by Y. There is no base-emitter or gate-source voltage
drop, so the emitter or source voltage (at X) follows the voltage at Y. The gate or base
has an infinite input impedance (Y), while the emitter or source has a zero input
impedance (X). Any current out of the emitter or source (X) is reflected at the collector or
drain (Z) as a current in, but with an infinite output impedance. Because of this reversal
of sense between X and Z currents, this ideal bipolar or field-effect transistor represents a
CCII−. If current flowing out of X resulted in the same high-impedance current flowing
out of Z, it would be a CCII+.
For an ideal CCII [3], the relation between the voltages and currents is given by the
hybrid matrix:
































Z
X
Y
Z
X
Y
V
I
V
I
V
I
010
001
000

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Third generation(CCIII)
Figure 7: Symbolic Notation of CCIII
The third configuration of the current conveyor is similar to the CCI except that the
current in X is reversed, so in a CCIII whatever current flows into Y also flows out .
The defining hybrid matrix equation of a dual output CCIII is given by:

































 Z
X
Y
Z
X
Y
V
I
V
I
V
I
010
001
010
Advantages
Current conveyors can provide better gain-bandwidth products than comparable op-
amps, under both small and large signal conditions. In instrumentation amplifiers, their
gain does not depend on the matching of pairs of external components, only on the
absolute value of a single circuit element.
Disadvantages
The current conveyors are not available in IC form.

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CURRENT FEEDBACK OPERATIONAL AMPLIFIER
The current feedback operational amplifier otherwise known as CFOA or CFA is a type
of electronic amplifier whose inverting input is sensitive to current, rather than to
voltage as in a conventional voltage-feedback operational amplifier (VFA)[1]. The CFA
was invented by David Nelson at Comlinear Corporation, and first sold in 1982 as a
hybrid amplifier, the CLC103. An early patent covering a CFA is U.S. Patent 4,502,020,
David Nelson and Kenneth Saller (filed in 1983). The integrated circuit CFAs were
introduced in 1987 by both Comlinear and Elantec (designer Bill Gross). They are
usually produced with the same pin arrangements as VFAs, allowing the two types to be
interchanged without rewiring when the circuit design allows. In simple configurations,
such as linear amplifiers, a CFA can be used in place of a VFA with no circuit
modifications, but in other cases, such as integrators, a different circuit design is
required. The classic four-resistor differential amplifier configuration also works with a
CFA, but the common-mode rejection ratio is poorer than that from a VFA.
A CFOA is a four terminal building block characterized by the following terminal
equations.[5]
zwxzyxy VVIIVVI  ,,,0
Figure 8: Symbolic Notation of CFOA

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The port relations of an ideal CFOA are described by the following hybrid matrix:





































W
Z
X
Y
W
Z
X
Y
I
V
I
V
V
I
V
I
0100
0010
0001
0000
Advantages
1. Ability to overcome gain bandwidth trade off
2. Slew rate limitation can be avoided
3. Available in IC form
Disadvantages
Disadvantages of CFAs include poorer input offset voltage and input bias current
characteristics. Additionally, the DC loop gains are generally smaller by about three
decimal orders of magnitude. Given their substantially greater bandwidths, they also
tend to be noisier. CFA circuits must never include a direct capacitance between the
output and inverting input pins as this often leads to oscillation. CFAs are ideally suited
to very high speed applications with moderate accuracy requirements

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OSCILLATORS
An Electronic Oscillator is an electronic circuit that produces a periodic, oscillating
electronic signal, often a sine wave or a square wave. Oscillators convert direct current
(DC) from a power supply to an alternating current signal. They are widely used in many
electronic devices.
An oscillator is a mechanical or electronic device that works on the principles
of Oscillation: A periodic fluctuation between two things based on changes in energy.
Computers, clocks, watches, radios, and metal detectors are among the many devices
that use oscillators. Common examples of signals generated by oscillators include
signals broadcast by radio and television transmitters, clock signals that regulate
computers and quartz clocks, and the sounds produced by electronic beepers and video
games.
Oscillators are often characterized by the frequency of their output signal:
1. A low-frequency oscillator (LFO) is an electronic oscillator that generates a
frequency below ≈20 Hz. This term is typically used in the field of audio synthesizers, to
distinguish it from an audio frequency oscillator.
2. An audio oscillator produces frequencies in the audio range, about 16 Hz to 20 kHz.
3. An RF oscillator produces signals in the radio frequency (RF) range of about 100
kHz to 100 GHz.
Oscillators are can also be characterized in terms of electronics oscillators:
1. Linear or harmonic oscillator
Ex. Hartley, Colpitts , Weinn bridge, Phase Shift.
2. Nonlinear or Relaxation oscillator

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PSPICE SIMULATION
Some Pspice Simulations Regarding Oscillator Design and show their 3 type
responses: Steady state , Transient and Fourier .
Phase Shift Oscillator using OPAMP
Circuit Diagram :
(taking r1=r2=r3=R , c1=c2=c3=C)
Figure 9: Phase shift oscillator using opamp
Pspice Code:
x1 0 2 3 4 5 ua741
r1 1 2 50.86k
r2 2 5 2200k
r3 1 0 10k
r4 6 0 10k
r5 7 0 10k
c1 1 6 10nf ic=0.01mA
c2 6 7 10nf ic=0.01mA
c3 7 5 10nf ic=0.01mA
v1 3 0 dc .8v
v2 0 4 dc .8v
.include ua741.cir
.tran 0 60ms 3us 1us uic

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.four .6497433khz 11 v(5)
.probe
.end
TransientResponse :
Time
0s 5ms 10ms 15ms 20ms 25ms 30ms 35ms 40ms 45ms 50ms 55ms 60ms
V(5)
-100mV
0V
100mV
200mV
300mV
400mV

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Steady State Response (2x Zoom) :
Condition of Oscillation:
29 = K => 2Rfb = 29R
Theoretical Frequency
𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 =
1
2𝜋𝐶𝑅√6
= 6.524K Hz
Total Harmonic Distortion:
5.1324749E PERCENT
Time
7.5ms 8.0ms 8.5ms 9.0ms 9.5ms 10.0ms 10.5ms 11.0ms 11.5ms 12.0ms 12.5ms 13.0ms 13.5ms 14.0ms 14.5ms
V(5)
0V
100mV
200mV
300mV
357mV

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Hartley Oscillator using OPAMP
Circuit Diagram :
Figure 10: Hartley oscillator using opamp
Pspice Code :
x1 0 1 2 3 4 ua741
r1 5 1 1k
r2 4 1 10k
l1 4 0 1uH
l2 5 0 1uH
c 5 4 3.7uf
v2 2 0 dc 5v
v3 3 0 dc -5v
.include ua741.cir
.tran 0 30ms 0.5us 0.5us uic
.four 58.53619602657705khz 11 v(4)
.probe v(4)
.end

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Transient Response :
Time
0s 2ms 4ms 6ms 8ms 10ms 12ms 14ms 16ms 18ms 20ms
V(4)
-1.2mV
-0.8mV
-0.4mV
0.0mV
0.4mV
0.8mV
1.2mV
Time
17.3200ms 17.3300ms 17.3400ms 17.3500ms 17.3600ms 17.3700ms 17.3800ms 17.3900ms 17.4000ms 17.4100ms 17.4200ms17.3115ms
V(4)
-1.2mV
-0.8mV
-0.4mV
0.0mV
0.4mV
0.8mV
1.2mV

24 | P a g e
Fourier Transform
1
2𝜋√ 𝐶(𝐿1 + 𝐿2)
= 58.59K Hz
6.11212749E+01 PERCENT
Frequency
0Hz 0.2MHz 0.4MHz 0.6MHz 0.8MHz 1.0MHz 1.2MHz 1.4MHz 1.6MHz 1.8MHz
V(4)
10nV
1.0uV
100uV
1.0nV
1.0mV

25 | P a g e
Colpitts Oscillator using OPAMP
Circuit Diagram :
Figure 11: Colpitts oscillator using opamp
Pspice Code :
x1 0 1 2 3 4 ua741
r1 5 1 1k
r2 4 1 10k
c1 4 0 1uf
c2 5 0 4.7uf
l 5 4 100uH
v2 2 0 dc 10v
v3 3 0 dc -10v
.include ua741.cir
.four 17.53593209731337khz 11 v(4)
.probe v(4)
.end

26 | P a g e
Time
V(4)
-6.0V
-4.0V
-2.0V
0V
2.0V
4.0V
6.0V
Time
2.08ms 2.10ms 2.12ms 2.14ms 2.16ms 2.18ms 2.20ms 2.22ms 2.24ms 2.26ms 2.28ms 2.30ms 2.32ms 2.34ms 2.36ms
V(4)
-6.0V
-4.0V
-2.0V
0V
2.0V
4.0V
6.0V

27 | P a g e
Fourier Transform
1
2𝜋√ 𝐿(𝐶1 ∗ 𝐶2)/(𝐶1 + 𝐶2)
= 10.389K Hz
8.941239E+01 PERCENT
Frequency
0Hz 0.2MHz 0.4MHz 0.6MHz 0.8MHz 1.0MHz 1.2MHz 1.4MHz 1.6MHz 1.8MHz
V(4)
100uV
10mV
1.0V
10uV
10V

28 | P a g e
Wien Bridge Oscillator using OPAMP
Circuit Diagram :
Figure 12: Wien Bridge oscillator using opamp
Pspice Code :
x1 1 5 3 4 2 ua741
r1 1 0 1k
c1 1 0 0.01uf
r2 1 6 1k
c2 6 2 0.01uf
ra 5 2 10.29k
rb 5 0 5k
vcc 3 0 dc 50
vee 4 0 dc -50
.include opamp.cir
.tran 0 50ms 0.01ms 0.01ms
.four 15.19khz 11 v(2)
.probe v(2)
.end
Charachteristic Equation :
S2C2R2 + SCR(3-k)+1 = 0, where k= 1 +
𝐑𝐀
𝐑𝐁

29 | P a g e
Time
V(4)
-15V
-10V
-5V
0V
5V
10V
15V
Time
28.100ms 28.200ms 28.300ms 28.400ms 28.500ms 28.600ms 28.700ms 28.800ms
V(4)
-15V
-10V
-5V
0V
5V
10V
15V

30 | P a g e
Fourier Transform
3 = K => 2RB = RA
1
2𝜋𝐶𝑅
= 15.19K Hz
Frequency
0Hz 0.5MHz 1.0MHz 1.5MHz 2.0MHz 2.5MHz 3.0MHz 3.5MHz 4.0MHz 4.5MHz 5.0MHz 5.5MHz
V(4)
1.0uV
100uV
10mV
1.0V
100nV
10V

31 | P a g e
Wien Bridge Oscillator using OTA
Circuit Diagram :
Figure 13: Wien Bridge oscillator using ota
Pspice Code :
x1 2 1 5 6 7 2 otac
x2 0 2 5 6 8 2 otac
x3 2 0 5 6 9 1 otac
ib1 7 0 dc 4.5uA
ib2 8 0 dc 4.2uA
ib3 9 0 dc 6uA
c1 2 0 1nf
c2 1 0 1nf
v3 5 0 dc 3v
v4 0 6 dc 3v
.include otac.cir
.four 15.7954khz 11 v(2)
.probe
.end.

32 | P a g e
TransientResponse:
Steady State Response(10xZoom)
Time
0s 2ms 4ms 6ms 8ms 10ms 12ms 14ms 16ms 18ms 20ms 22ms 24ms 26ms 28ms 30ms
V(2)
-20mV
-10mV
0V
10mV
20mV
Time
11.800ms 11.900ms 12.000ms 12.100ms 12.200ms 12.300ms 12.400ms 12.500ms 12.600ms 12.700ms 12.800ms 12.900ms
V(2)
-20mV
-10mV
0V
10mV
20mV

33 | P a g e
Fourier Transform
Theoretical Frequency:
√
𝑔𝑚1∗𝑔𝑚2
𝐶1∗𝐶2
= 3.38 KHz
Frequency
0Hz 5KHz 10KHz 15KHz 20KHz 25KHz 30KHz 35KHz 40KHz 45KHz 50KHz
V(1)
10nV
1.0uV
100uV
10mV
1.0nV
100mV
3.1 K

34 | P a g e
An Oscillator using CFOA
Circuit Diagram :
Figure 14: Oscillator using Cfoa
Pspice Code :
X1 1 2 3 4 5 6 AD844/AD
r3 1 0 11k
r4 2 0 10k
c1 1 5 1.2nf ic=0.001na
c0 6 0 1.2nf ic=0.001na
r7 2 6 50k
vcc 3 0 dc 10v
vee 0 4 dc 10v
.include cfoa.cir
.probe
.tran 0 20ms .5us .5us uic
.end
Characteristic Equation :
S2[R2R3R4C0C6] + S[-R2R3C6+R2R4C0+C6R2R4] + R4 = 0

35 | P a g e
TOTAL RESPONSE (NO ZOOM) :
Fourier Transform :
Frequency
0Hz 0.1KHz 0.2KHz 0.3KHz 0.4KHz 0.5KHz 0.6KHz
V(4)
1.0mV
10mV
100mV
1.0V
10V
104Hz
Time
0s 20ms 40ms 60ms 80ms 100ms 120ms 140ms 160ms 180ms 200ms 220ms 240ms 260ms
V(4)
-8.0V
-4.0V
0V
4.0V
8.0V

36 | P a g e
1 +
𝐶0
𝐶6
<=
𝑅3
𝑅4
60312
1
CCRR
Frequency


= 109 Hz
8.625649E PERCENT

37 | P a g e
FILTERS
Filters are networks that process signals in a frequency-dependent manner. The basic
concept of a filter can be explained by examining the frequency dependent nature of the
impedance of capacitors and inductors. Consider a voltage divider where the shunt leg is
reactive impedance. As the frequency is changed, the value of the reactive impedance
changes, and the voltage divider ratio changes. This mechanism yields the frequency
dependent change in the input/output transfer function that is defined as the frequency
response.
Filters have many practical applications. A simple, single-pole, low-pass filter (the
integrator) is often used to stabilize amplifiers by rolling off the gain at higher
frequencies where excessive phase shift may cause oscillations.
A simple, single-pole, high-pass filter can be used to block dc offset in high gain
Amplifiers or single supply circuits. Filters can be used to separate signals, passing
those of interest, and attenuating the unwanted frequencies.
Electronic filters are analog circuits which perform signal processingfunctions,
specifically to remove unwanted frequency components from the signal, to enhance
wanted ones, or both. Electronic filters can be:
 Passive or Active
 High-pass, low-pass, Band-pass, Band-stop , All-pass, Universal Filters.
 Discrete-time (sampled) or Continuous-time
 Linear or Non-linear
 Infinite impulse response (IIR type) or Finite impulse response (FIR type)
Here in this context we shall discuss the top 2 filter types, as per the report is
concerned.

38 | P a g e
LOW PASS FILTER
A low-pass filter is a filter that passes signals with a frequency lower than a
certain cut-off frequency and attenuates signals with frequencies higher than the cut-
off frequency. The amount of attenuation for each frequency depends on the filter
design.
HIGH PASS FILTER
A high-pass filter is an electronic filter that passes signals with a frequency higher
than a certain cut-off and attenuates signals with frequencies lower than the cut-off
frequency. The amount of attenuation for each frequency depends on the filter design
BAND PASS FILTER
A band-pass filter is a device that passes frequencies within a certain range and
rejects (attenuates) frequencies outside that range.
BAND REJECTFILTER
A band-pass filter is a device that rejects (attenuates) frequencies within a certain
range and passes frequencies outside that range.
ALL PASS FILTER
An all-pass filter is a signal processing filter that passes all frequencies equally in
gain, but changes the phase relationship between various frequencies. It does this by
varying its phase shift as a function of frequency. Generally, the filter is described by
the frequency at which the phase shift crosses 90° (i.e., when the input and output
signals go into quadrature – when there is a quarter wavelength of delay between
them).

39 | P a g e
UNIVERSAL FILTER
A universal filter is a special type of filter which can realize all types of filters listed
above in one circuit without changing the topology of the circuit.
The transfer function of a
High-pass filter is: 22
2
)(
o
o
o
s
Q
s
sH
sH




Low-pass filter is: 22
)(
o
o
o
s
Q
s
H
sH




Band-pass filter is: 22
2
0
)(
o
o
o
s
Q
s
H
sH





Band-reject filter is: 22
22
0 )(
)(
o
o
o
s
Q
s
sH
sH






All-pass filter is : 22
2
0
2
)(
o
o
o
s
Q
s
s
Q
s
sH







From the characteristic Equation we can find out the nature of filter appearing at the
output of the filer.
PASSIVE FILTERS

40 | P a g e
Passive implementations of linear filters are based on combinations of
resistors (R), inductors (L) and capacitors (C). These types are collectively known
as passive filters, because they do not depend upon an external power supply and/or
they do not contain active components such as transistors.
SIMULATIONS
Figure 15: Implementation of Passive All-pass filter
Frequency
10Hz 30Hz 100Hz 300Hz 1.0KHz 3.0KHz 10KHz 30KHz 100KHz 300KHz 1.0MHz
V(3,2)/ V(1)
200m
400m
600m
800m
SEL>>
FREQUENCY RESPONSE
P(V(3,2))
-200d
-100d
0d
PHASE RESPONSE

41 | P a g e
Figure 16: Implementation of Passive Low-pass filter
Frequency
V(3)/ V(5) V(2)/ V(1)
0
0.5
1.0
15.908K- CUT-OFF FREQUENCY5.9456K - CUT-OFF FREQUENCY
FIRST ORDERSECOND ORDER
P(V(2)) P(V(3))
-200d
-100d
0d
SEL>>
FIRST ORDERSECOND ORDER

42 | P a g e
Figure 17: Implementation of Passive High-pass filter
r
Frequency
V(2)/ V(1) V(3)/ V(5)
0
400m
800m
1100m
SECOND ORDERFIRST ORDER
42.771K- CUT-OFF FREQUENCY15.879K- CUT-OFF FREQUENCY
P(V(3)) P(V(2))
0d
90d
180d
SEL>>
PHASE RESPONSE
SECOND ORDER
FIRST ORDER

43 | P a g e
Figure 18: Implementation of Passive Band-pass filter
Frequency
10Hz 30Hz 100Hz 300Hz 1.0KHz 3.0KHz 10KHz 30KHz 100KHz 300KHz 1.0MHz 3.0MHz 10MHz 30MHz 100MHz
V(7)/ V(5)
0
200m
400m
SEL>>
48.6K BANDWIDTH
16.444K-CENTRAL FREQUENCY
4.7424K-LOW CUT-OFF FREQUENCY 53.334K- HIGH CUT-OFF FREQUENCY
P(V(7))
-100d
0d
100d
PHASE RESPONSE

44 | P a g e
ACTIVE FILTERS
An active filter is a type of analog electronic filter that uses active components such as
an amplifier. Amplifiers included in a filter design can be used to improve the
performance and predictability of a filter, while avoiding the need for inductors (which
are typically expensive compared to other components). An amplifier prevents the load
impedance of the following stage from affecting the characteristics of the filter. An
active filter can have complex poles and zeros without using a bulky or expensive
inductor.
SIMULATIONS
LPF (OPAMP)
Circuit diagram:
Figure 13: Lpf(2nd order) using opamp
Pspice Code:
x1 0 1 2 3 4 ua741
vin 6 0 ac 10mv
v2 2 0 dc 12v
v3 0 3 dc 12v
r1 6 5 2.4k
r2 5 4 4.8k
r3 5 1 8k
c1 5 0 0.1uf
c2 4 1 8nf

45 | P a g e
.include ua741.cir
.ac dec 10 10hz 100khz
.probe
.end
Output:
HPF (OPAMP)
Circuit diagram:
Figure 20: Hpf(2nd order) using opamp
Frequency
10Hz 30Hz 100Hz 300Hz 1.0KHz 3.0KHz 10KHz 30KHz 100KHz
V(4)/ V(6)
0
1.0
2.0
3.0
(0.974K,1.4057)Cut-off Frequency
GAIN(DB)
P(V(4))
50d
100d
150d
-10d
SEL>> PHASE RESPONSE

46 | P a g e
Pspice Code:
x1 1 2 3 4 5 ua741
v3 3 0 dc 10v
v4 0 4 dc 10v
vin 7 0 ac 1mv
r1 2 0 10k
r2 6 5 10k
c1 7 6 0.01uf
c2 6 2 0.01uf
ra 1 5 6k
rb 1 0 10k
.include ua741.cir
.probe
.end
Output:
Frequency
V(5)/ V(7)
0
1.0
2.0
1.5732K-CUT-OFF FREQUENCY
GAIN(DB)
P(V(5))
0d
93d
-100d
180d
SEL>>
PHASE RESPONSE

47 | P a g e
BPF (OPAMP)
Circuit diagram:
Figure 21: Bpf(2nd order) using opamp
Pspice Code:
x1 1 2 3 4 5 ua741
v3 3 0 dc 10v
v4 0 4 dc 10v
vin 6 0 ac 10mv
r1 6 7 10k
r2 2 0 10k
r3 5 7 10k
c1 7 0 0.01uf
c2 7 2 0.01uf
ra 1 0 6k
rb 1 5 10k
.ac dec 1000 10hz 1megahz
.include ua741.cir
.probe
.end

48 | P a g e
Output:
BRF (OPAMP)
Circuit diagram:
Figure 22: Brf(2nd order) using opamp
Pspice Code:
x1 1 2 3 4 5 ua741
v3 3 0 dc 10v
v4 0 4 dc 10v
vin 7 0 ac 10mv
Frequency
V(5)/ V(6)
0
1.0
2.0
2.1815K BANDWIDTH
3.6141K-HIGH CUT-OFF FREQUENCY
2.2751K-CENTRAL FREQUENCY
1.4289K-LOW CUT-OFF FREQUENCY
P( V(5))
-100d
0d
100d
SEL>>
PHASE RESPONSE

49 | P a g e
rb 1 0 10k
ra 1 5 5k
c1 7 8 0.005uf
c2 8 2 0.005uf
c3 6 0 0.01uf
r1 7 6 10k
r2 6 2 10k
r3 8 5 5k
.include ua741.cir
.probe
.end
Output:
Frequency
V(5)/ V(7)
0
1.0
2.0
(3.1623K,19.730m)
(1.9537K,1.0664) (5.1186K,1.0655)
P(V(5))
-100d
0d
100d
SEL>>
PHASE RESPONSE
(3.2589K,88.397)
(3.1386K,-87.188)

50 | P a g e
Universal Filter (1) using OTA
Circuit Diagram
Figure 23: Universal Filter-1 using ota
Pspice Code
universal2(without short)hpf
x1 1 2 3 4 5 6 otac
x2 6 0 3 4 5 2 otac
x3 9 2 3 4 5 2 otac
vcc 3 0 dc 10V
vee 0 4 dc 10V
Ib1 5 0 dc 220uA
c1 6 0 19nf
c2 2 10 10nf
v1 1 0 AC 0mv
v2 9 0 AC 0mv
v3 10 0 AC 30mv
.include otac.cir
.probe
.AC DEC 1000 10Hz 10MegHz
.end
*universal2(without short)lpf
x1 1 2 3 4 5 6 otac
x2 6 0 3 4 5 2 otac
x3 9 2 3 4 5 2 otac

51 | P a g e
vcc 3 0 dc 10V
vee 0 4 dc 10V
Ib1 5 0 dc 220uA
c1 6 0 19nf
c2 2 10 10nf
v1 1 0 AC 30mv
v2 9 0 AC 0mv
v3 10 0 AC 0mv
.include otac.cir
.probe
.end
*universal2(without short)bpf
x1 1 2 3 4 5 6 otac
x2 6 0 3 4 5 2 otac
x3 9 2 3 4 5 2 otac
vcc 3 0 dc 10V
vee 0 4 dc 10V
Ib1 5 0 dc 220uA
c1 6 0 19nf
c2 2 10 10nf
v1 1 0 AC 0mv
v2 9 0 AC 30mv
v3 10 0 AC 0mv
.include otac.cir
.probe
.end
*universal2(without short)brf
x1 1 2 3 4 5 6 otac
x2 6 0 3 4 5 2 otac
x3 9 2 3 4 5 2 otac
vcc 3 0 dc 10V
vee 0 4 dc 10V
Ib1 5 0 dc 220uA
c1 6 0 19nf
c2 2 10 10nf
v1 1 0 AC 30mv
v2 9 0 AC 0mv
v3 10 0 AC 30mv
.include otac.cir
.probe

52 | P a g e
.end
*universal2(without short)apf
x1 1 2 3 4 5 6 otac
x2 6 0 3 4 5 2 otac
x3 9 2 3 4 5 2 otac
vcc 3 0 dc 10V
vee 0 4 dc 10V
Ib1 5 0 dc 220uA
c1 6 0 19nf
c2 2 10 10nf
v1 1 0 AC 30mv
v2 0 9 AC 30mv
v3 10 0 AC 30mv
.include otac.cir
.probe
.end
Characteristic equation
𝑠2
𝑐2
𝑉𝑐 + 𝑠𝑐𝑔𝑚𝑉𝑏 + 𝑔𝑚2
𝑉𝑎
𝑠2 𝑐2 + 𝑠𝑐𝑔𝑚 + 𝑔𝑚2
So from the characteristic equation following conditions are obtained:
1. Low pass filter when Vc = Vb = 0
2. High pass filter when Vb = Va = 0
3. Band pass filter when Vc = Va = 0
4. Band reject filter when Vc = Va = -Vb
5. All pass filter when all are applied

53 | P a g e
Output
Universal Filter (2) using OTA
Circuit Diagram
Figure 24: Universal Filter-2 using ota
Frequency
10Hz 30Hz 100Hz 300Hz 1.0KHz 3.0KHz 10KHz 30KHz 100KHz 300KHz 1.0MHz 3.0MHz 10MHz
V(2)
0V
10mV
20mV
30mV
40mV

54 | P a g e
Pspice Code :
**ota filter(low)**
x1 1 2 3 4 5 6 ota
x2 6 2 9 10 11 2 ota
c1 6 7 3nf
c2 2 12 .3nf
va 1 0 ac 10mv
vb 7 0 ac 0mv
vc 12 0 ac 0mv
v3 3 0 dc 10v
v4 0 4 dc 10v
v9 9 0 dc 10v
v10 0 10 dc 10v
ib1 5 0 dc 80uA
ib2 11 0 dc 80uA
.include ota.cir
.probe
.end
**ota filter(high)**
x1 1 2 3 4 5 6 ota
x2 6 2 9 10 11 2 ota
c1 6 7 30nf
c2 2 12 3nf
va 1 0 ac 0mv
vb 7 0 ac 0mv
vc 12 0 ac 10mv
v3 3 0 dc 10v
v4 0 4 dc 10v
v9 9 0 dc 10v
v10 0 10 dc 10v
ib1 5 0 dc 80uA
ib2 11 0 dc 80uA
.include ota.cir
.probe
.end
**ota filter(bpf)**
x1 1 2 3 4 5 6 ota
x2 6 2 9 10 11 2 ota
c1 6 7 3nf

55 | P a g e
c2 2 12 3nf
va 1 0 ac 0mv
vb 7 0 ac 10mv
vc 12 0 ac 0mv
v3 3 0 dc 10v
v4 0 4 dc 10v
v9 9 0 dc 10v
v10 0 10 dc 10v
ib1 5 0 dc 80uA
ib2 11 0 dc 80uA
.include ota.cir
.probe
.end
**ota filter(brf)**
x1 1 2 3 4 5 6 ota
x2 6 2 9 10 11 2 ota
c1 6 7 3nf
c2 2 12 3nf
va 1 0 ac 10mv
vb 7 0 ac 0mv
vc 12 0 ac 10mv
v3 3 0 dc 10v
v4 0 4 dc 10v
v9 9 0 dc 10v
v10 0 10 dc 10v
ib1 5 0 dc 80uA
ib2 11 0 dc 80uA
.include ota.cir
.probe
.end
**ota filter(brf)**
x1 1 2 3 4 5 6 ota
x2 6 2 9 10 11 2 ota
c1 6 7 3nf
c2 2 12 3nf
va 1 0 ac 10mv
vb 7 0 ac 0mv
vc 12 0 ac 10mv
v3 3 0 dc 10v
v4 0 4 dc 10v
v9 9 0 dc 10v

56 | P a g e
v10 0 10 dc 10v
ib1 5 0 dc 80uA
ib2 11 0 dc 80uA
.include ota.cir
.probe
.end
**ota filter(brf)**
x1 1 2 3 4 5 6 ota
x2 6 2 9 10 11 2 ota
c1 6 7 3nf
c2 2 12 3nf
va 1 0 ac 10mv
vb 0 7 ac 10mv
vc 12 0 ac 10mv
v3 3 0 dc 10v
v4 0 4 dc 10v
v9 9 0 dc 10v
v10 0 10 dc 10v
ib1 5 0 dc 80uA
ib2 11 0 dc 80uA
.include ota.cir
.probe
.end

57 | P a g e
Output:
Characteristic equation
𝑠2
𝑐2
𝑉𝑐 + 𝑠𝑐𝑔𝑚𝑉𝑏 + 𝑔𝑚2
𝑉𝑎
𝑠2 𝑐2 + 𝑠𝑐𝑔𝑚2 𝑅 + 𝑔𝑚2
So from the characteristic equation following conditions are obtained:
 Low pass filter when Vc = Vb = 0
 High pass filter when Vb = Va = 0
 Band pass filter when Vc = Va = 0
 Band reject filter when Vc = Va = -Vb
 All pass filter when all are applied
Frequency
100Hz 300Hz 1.0KHz 3.0KHz 10KHz 30KHz 100KHz 300KHz 1.0MHz 3.0MHz 10MHz 30MHz 100MHz
V(2)
0V
2mV
4mV
6mV
8mV
10mV
12mV

58 | P a g e
Amplitude Modulator using OTA
Circuit Diagram :
Figure 25:Implementing DSB-AM using ota
Pspice Code :
X1 3 2 5 60 70 6 ota14
.param val=100k
R1 3 0 51
R2 2 0 51
R3 2 7 47k
R4 6 0 5.1k
R5 5 1 {val}
v 7 0 dc 1v
V1 1 0 sin(0 1v 5khz)
V2 3 0 sin(0 .5v 10khz)
vcc 60 0 dc 3V
vee 70 0 dc -3V
.include ota14.cir
*.step param val 90k 100k 5k
.tran 0 100ms .1ms .1ms
.probe
.end

59 | P a g e
Critical Modualtion.
Time
0s0.5ms1.0ms1.5ms2.0ms2.5ms3.0ms3.5ms4.0ms4.5ms5.0ms
V(1)V(5)
-5.0V
0V
5.0V

60 | P a g e
Under ModulationTime
0s1ms2ms3ms4ms5ms6ms
V(1)V(6)
0V
1.0V
-1.2V
SEL>>
V(5)
-200mV
0V
200mV

61 | P a g e
Over Modulation (DISTORTION IS CLEARLY SEEN)Time
0s1ms2ms3ms4ms5ms6ms
V(1)V(6)
-2.0V
0V
2.0V
V(5)
-400mV
0V
400mV
SEL>>

62 | P a g e
TRANSLINEAR CIRCUITS
History and Background
A translinear circuit is a circuit that carries out its function using the translinear
principle. These are current-mode circuits that can be made using transistors that obey an
exponential current-voltage characteristic—this includes BJTs and CMOS transistors in
weak inversion.
The word translinear (TL) was invented by Barrie Gilbert in 1975 to describe circuits
that used the exponential current-voltage relation of BJTs. By using this exponential
relationship, this class of circuits can implement multiplication, amplification and
power-law relationships. When Barrie Gilbert described this class of circuits he also
described the translinear principle (TLP) which made the analysis of these circuits
possible in a way that the simplified view of BJTs as linear current amplifiers did not
allow. TLP was later extended to include other elements that obey an exponential
current-voltage relationship (such as CMOS transistors in weak inversion).
Usage in present electronics scenario
The TLP has been used in a variety of circuits including vector arithmetic
circuits,[6] current conveyors, current-mode operational amplifiers, and RMS-DC
converters.[7] It has been in use since the 1960s (by Gilbert), but was not formalized
until 1975.[1] In the 1980s, Evert Seevinck's work helped to create a systematic process
for translinear circuit design. In 1990 Seevinck invented a circuit he called a
companding current-mode integrator[8] that was effectively a first-order log-domain
filter. A version of this was generalized in 1993 by Douglas Frey and the connection
between this class of filters and TL circuits was made most explicit in the late 90s work

63 | P a g e
of Jan Mulder et al. where they describe thedynamic translinear principle. More work by
Seevinck led to synthesis techniques for extremely low-power TL circuits.[9] More
recent work in the field has led to the voltage-translinear principle, multiple-input
translinear element networks, and field-programmable analog arrays (FPAAs).
Principle
Figure 26: Arrangement of transistors in transliner fashion
Here each BJT is considered to be identical with large β.
So,
ICO1 = ICO2 = ICO3 = ICO4 and
ic = Ico eVBE/ηVT
=> VBE = ηVT ln (ic / ICO)
Now applying KVL,
VBE1 + VBE2 = VBE3 + VBE4 ...2
So using 1 and 2 we get:
ic1 * ic2 = ic3 * ic4
... 1

64 | P a g e
References
1. Dr. Raj Senani , D.R. Bhaskar, A. K. Singh, V. K. Singh “Current Feedback
Operational Amplifiers and Their Applications”.
2. Dr. Raj Senani , D. R. Bhaskar, A. K. Singh, “Current Conveyors: Variants,
Applications and Hardware Implementations”.
3. Operation Transconductance Amplifier, Achim Gratz
4. https://en.wikipedia.org/wiki/Operational_transconductance_amplifier
5. Op-amps and Linear Integrated Circuits by Ramakant A. Gayakwad.
6. Spice For Circuits And Electronics Using Pspice by Rashid Muhammad H

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