03/07/15 Prof.Satheesh MB, INA, Ezhimala
Operational-Amplifier and its Applications
Course: 90 INAC-L&X
AT-15
Prof.Satheesh Monikandan [email protected]
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Outline
• Introduction • The 741 Op-Amp Circuit• The ideal Op Amp• The inverting configuration • The non-inverting configuration• Integrator and differentiator
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Introduction
• Analog ICs include operational amplifiers, PLL, etc.
• A complete op amp is realized by combining analog circuit building blocks.
• The bipolar op-amp has the general purpose variety and is designed to fit a wide range of specifications.
• The terminal characteristics is nearly ideal.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The 741 Op-Amp Circuit
• General description
• The input stage
• The intermediate stage
• The output stage
• The biasing circuits
• Device parameters
03/07/15 Prof.Satheesh MB, INA, Ezhimala
BLOCK DIAGRAM
03/07/15 Prof.Satheesh MB, INA, Ezhimala
General Description
• 20 transistors, few resistors and only one capacitor
• Two power supplies
• Short-circuit protection
03/07/15 Prof.Satheesh MB, INA, Ezhimala
PIN DIAGRAM
03/07/15 Prof.Satheesh MB, INA, Ezhimala
ARCHITECTURE
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The Ideal Op Amplifier
Symbol for the op amp
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The Ideal Op Amplifier
The op amp shown connected to dc power supplies.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Characteristics of the Ideal Op Amplifier
• Differential input resistance is infinite.• Differential voltage gain is infinite.• CMRR is infinite.• Bandwidth is infinite.• Output resistance is zero.• Offset voltage and current is zero.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Equivalent Circuit of the Ideal Op Amp
03/07/15 Prof.Satheesh MB, INA, Ezhimala
FREQUENCY RESPONSE
03/07/15 Prof.Satheesh MB, INA, Ezhimala
TRANSFER CHARACTERISTICS
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The Inverting Configuration
The inverting closed-loop configuration.
Virtual ground.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The Inverting Configuration
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The Inverting Configuration
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The Inverting Configuration
• Shunt-shunt negative feedback• Closed-loop gain depends entirely on passive
components and is independent of the op amplifier.
• Engineer can make the closed-loop gain as accurate as he wants as long as the passive components are accurate.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
I/O WAVEFORM
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The Non-inverting Configuration
The non-inverting configuration.
Series-shunt negative feedback.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The Non-inverting Configuration
03/07/15 Prof.Satheesh MB, INA, Ezhimala
I/O WAVEFORM
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The Voltage follower
(a) The unity-gain buffer or follower amplifier.
(b) Its equivalent circuit model.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
I/O WAVEFORM
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The Weighted Summer
03/07/15 Prof.Satheesh MB, INA, Ezhimala
A Single Op-Amp Difference Amplifier
Linear amplifier.
Theorem of linear Superposition.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
A Single Op-Amp Difference Amplifier
Application of superposition
Inverting configuration
v o1=−R2
R1
v I1
03/07/15 Prof.Satheesh MB, INA, Ezhimala
A Single Op-Amp Difference Amplifier
Application of superposition.
Non-inverting configuration.
v o2=(1+R2
R1
)(R4
R4+R3v) I2
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Integrators
The inverting configuration with general impedances in the feedback and the feed-in paths.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The Inverting Integrators
The Miller or inverting integrator.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Frequency Response of the integrator
03/07/15 Prof.Satheesh MB, INA, Ezhimala
I/O WAVEFORM
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The op-amp Differentiator
03/07/15 Prof.Satheesh MB, INA, Ezhimala
The op-amp Differentiator
Frequency response of a differentiator with a time-constant CR.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
I/O WAVEFORM
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Bistable Circuit
The bistable circuit (positive feedback loop)
The negative input terminal of the op amp connected to an input signal vI.
v+=voR1
R1+R2=vo β
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Bistable Circuit
The transfer characteristic of the circuit in (a) for increasing vI.
Positive saturation L+ and negative saturation L-
V TH =L+ β
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Bistable Circuit
The transfer characteristic for decreasing vI.
V TL=L− β
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Bistable Circuit
The complete transfer characteristics.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Application of Bistable Circuit as a Comparator
• Comparator is an analog-circuit building block used in a variety applications.
• To detect the level of an input signal relative to a preset threshold value.
• To design A/D converter.• Include single threshold value and two threshold
values.• Hysteresis comparator can reject the interference.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Application of Bistable Circuit as a Comparator
Block diagram representation and transfer characteristic for a comparator having a reference, or threshold, voltage VR.
Comparator characteristic with hysteresis.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Application of Bistable Circuit as a Comparator
Illustrating the use of hysteresis in the comparator characteristics as a means of rejecting interference.
03/07/15 Prof.Satheesh MB, INA, Ezhimala
Generation of Square Waveforms
The circuit obtained when the bistable multi-vibrator is implemented with the positive feedback loop circuit.