Electronic Devices & Circuits - Operational Amplifiers (Op-Amps) University Name: Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal System: CBCS/CBGS Program: Bachelor of Engineering in Computer Science Semester: 3 Subject: Electronic Devices & Circuits Description: This comprehensive PDF study material explores Operational Amplifiers (Op-Amps) in Electronic Devices & Circuits for Semester 3 of the Bachelor of Engineering in Computer Science program at Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal. Op-Amps are fundamental in analog circuits, known for their versatility and high gain. Topics covered include Op-Amp characteristics (high input impedance, low output impedance, etc.), slew rate, full power bandwidth, offset voltage, bias current, and practical applications like inverting/non-inverting amplifiers, differentiators, integrators, differential amplifiers, instrumentation amplifiers, and more. This resource equips students to design and analyze electronic circuits, addressing real-world engineering challenges in communication systems, signal processing, instrumentation, etc.

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Unit-4: Operational Amplifiers
(Op-Amps)
1. Operational Amplifier Characteristics: Operational amplifiers (op-amps) are highly versatile
electronic devices widely used in analog electronic circuits for various applications. Let's explore
the key characteristics in more detail:
● High Input Impedance: Op-amps have an extremely high input impedance, often in the
order of megaohms or gigaohms. This property makes them ideal for interfacing with
voltage sources without drawing significant current, ensuring minimal signal distortion
and loading effects.
● Low Output Impedance: An ideal op-amp has zero output impedance, allowing it to
drive loads without affecting the output voltage. While real-world op-amps have low
output impedance (typically a few ohms), it is significantly lower than typical load
impedances, ensuring good output signal fidelity.
● Open-Loop Gain (A_OL): The open-loop gain represents the amplification
provided by an op-amp when no feedback is applied. In ideal op-amps, this gain is
infinite. However, practical op-amps have very high open-loop gains, usually in the range
of 100,000 to 1,000,000. This high gain allows op-amps to amplify small input signals to
a much larger output.
● Common-Mode Rejection Ratio (CMRR): CMRR is a measure of an op-amp's ability to
reject common-mode signals that appear at both input terminals. It is expressed in
decibels (dB) and indicates the op-amp's ability to suppress noise or interference that
affects both inputs simultaneously. Higher CMRR values imply better rejection of
common-mode noise.
2. Slew Rate: The slew rate is a crucial parameter in op-amps that indicates how fast the output
voltage can change in response to a rapidly changing input. It is defined as the maximum rate of
change of the output voltage with respect to time. Slew rate is typically specified in volts per
microsecond (V/μs). Op-amps with higher slew rates are better suited for applications dealing
with high-frequency signals, such as audio and video amplification.
3. Full Power Bandwidth: The full power bandwidth is the frequency range over which an
op-amp can deliver its maximum output power while maintaining adequate performance. It is

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determined by the gain-bandwidth product (GBW), which is the product of the open-loop gain
and the bandwidth. The full power bandwidth is essential in applications where the op-amp
needs to handle signals with significant bandwidth, such as high-frequency audio or
radio-frequency applications.
4. Offset Voltage: Offset voltage is a small voltage difference that exists between the two input
terminals of an op-amp when the output voltage is at zero. In an ideal op-amp, this offset
voltage is zero. However, in practical op-amps, there is always some mismatch in the transistor
characteristics, leading to a small offset voltage. In precision applications, this offset voltage can
cause errors, so designers use techniques like auto-zeroing and chopper stabilization to
minimize its impact.
5. Bias Current: Bias current refers to the small amount of current that flows into the input
terminals of an op-amp. It arises due to the mismatch in transistor characteristics within the
op-amp. Bias currents are typically in the nanoampere range, but they can cause voltage drops
and offset voltage errors, especially in high-impedance circuits. Designers must account for bias
currents in their circuit designs to ensure proper functionality and accuracy.
6. Op-Amp Applications: Op-amps are fundamental building blocks of analog electronic
circuits, and their applications are diverse and widespread. Let's explore some common op-amp
applications in more detail:
● Voltage Follower (Unity-Gain Buffer): The voltage follower is a simple op-amp
configuration with a voltage gain of 1. It provides high input impedance and low output
impedance, allowing it to replicate the input voltage at the output without amplification.
Voltage followers are widely used to isolate different circuit stages, prevent signal
loading, and improve impedance matching.
● Inverting Amplifier: The inverting amplifier is a popular op-amp configuration where the
input signal is connected to the inverting input terminal. The output signal is obtained at
the junction of the input resistor and the feedback resistor. The voltage gain of the
inverting amplifier is negative and is determined by the ratio of the feedback resistor to
the input resistor. Inverting amplifiers are commonly used for signal inversion and
amplification, and they find applications in audio processing, instrumentation, and signal
conditioning.
● Non-Inverting Amplifier: The non-inverting amplifier configuration provides a
non-inverted output signal concerning the input. The input signal is connected to the
non-inverting input terminal, and the gain is determined by the ratio of the feedback
resistor to the input resistor. Non-inverting amplifiers are preferred in applications where
a positive gain is required, and they are often used in audio amplifiers and voltage
follower circuits.

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● Summing Amplifier (Summer): The summing amplifier is an op-amp circuit that
combines multiple input signals with different gain factors and sums them at the output. It
is widely used in analog computation, audio mixing, and signal processing applications.
The summing amplifier finds applications in audio mixers, signal averaging, and
instrumentation.
● Differentiator: The differentiator is an op-amp circuit that performs the mathematical
operation of differentiation on the input voltage. The output voltage of the differentiator is
proportional to the rate of change (derivative) of the input voltage with respect to time.
Differentiators are used in applications like waveform shaping, frequency differentiation,
and phase-shift circuits.
● Integrator: The integrator is an op-amp circuit that performs the mathematical operation
of integration on the input voltage. The output voltage of the integrator is proportional to
the accumulated area under the input waveform with respect to time. Integrators are
used in applications like analog filters, waveform generation, and frequency-domain
analysis.
● Differential Amplifier: The differential amplifier is designed to amplify the voltage
difference between two input signals while rejecting any common-mode signal that
appears on both inputs. It is crucial in applications where precise differential
measurements are necessary, such as instrumentation, communication systems, and
balanced audio circuits.
● Instrumentation Amplifier: The instrumentation amplifier is a specialized type of
differential amplifier designed to amplify small differential signals while rejecting
common-mode noise. It typically consists of multiple op-amp stages with precision
resistors. Instrumentation amplifiers are widely used in precision measurement
applications, such as strain gauge measurement, medical equipment, and sensor
interfaces.
● Logarithmic and Antilogarithmic Amplifiers: Logarithmic amplifiers (log amps) and
antilogarithmic amplifiers (antilog amps) are circuits used to perform logarithmic and
exponential functions, respectively. Logarithmic amplifiers compress input signals,
making them useful in applications where signals cover a wide dynamic range, such as
audio processing and signal compression. Antilogarithmic amplifiers expand input
signals and find application in signal generation and modulation.
● Voltage-to-Current and Current-to-Voltage Converters: These converters are used to
interface between voltage and current domains. Voltage-to-current converters convert
voltage signals into corresponding current signals, while current-to-voltage converters
perform the opposite conversion. These circuits are employed in various applications,
such as current sensors, current loop interfaces, and transimpedance amplifiers for
photodetectors.

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● Comparators and Schmitt Triggers: Comparators are high-gain differential amplifiers
used to compare two input voltages and produce digital outputs based on their
relationship. Schmitt triggers are a type of comparator with hysteresis, which provides
noise immunity in digital circuits. Comparators and Schmitt triggers are vital components
in various digital applications, such as voltage-level detection, zero-crossing detectors,
and pulse shaping.
In conclusion, the study of Operational Amplifiers in the subject of Electronic Devices & Circuits
for Semester 3 of the Bachelors of Engineering in Computer Science program at Rajiv Gandhi
Proudyogiki Vishwavidyalaya, Bhopal, provides students with a comprehensive understanding
of op-amp characteristics, applications, and circuit configurations. This knowledge equips
students to design and analyze a wide range of analog circuits used in communication systems,
signal processing, instrumentation, and other fields where precise signal amplification and
manipulation are required. Understanding op-amps is essential for aspiring engineers in their
journey of exploring and implementing electronic devices and circuits to solve real-world
engineering challenges.