# cmos opamp design

The operational amplifier is arguably the most useful single device in analog electronic circuitry. With only a handful of external components, it can be made to perform a wide variety of analog signal processing tasks. It is also quite affordable, most general-purpose amplifiers selling for under a dollar apiece. Modern designs have been engineered with durability in mind as well: several “op-amps” are manufactured that can sustain direct short-circuits on their outputs without damage. One key to the usefulness of these little circuits is in the engineering principle of feedback, particularly negativefeedback, which constitutes the foundation of almost all automatic control processes. The principles presented here in operational amplifier circuits, therefore, extend well beyond the immediate scope of electronics. It is well worth the electronics student’s time to learn these principles and learn them well. If the input voltages to this amplifier represented mathematical quantities (as is the case within analog computer circuitry), or physical process measurements (as is the case within analog electronic instrumentation circuitry), you can see how a device such as a differential amplifier could be very useful. We could use it to compare two quantities to see which is greater (by the polarity of the output voltage), or perhaps we could compare the difference between two quantities (such as the level of liquid in two tanks) and flag an alarm (based on the absolute value of the amplifier output) if the difference became too great. In basic automatic control circuitry, the quantity being controlled (called theprocess variable) is compared with a target value (called the setpoint), and decisions are made as to how to act based on the discrepancy between these two values. The first step in electronically controlling such a scheme is to amplify the difference between the process variable and the setpoint with a differential amplifier. In simple controller designs, the output of this differential amplifier can be directly utilized to drive the final control element (such as a valve) and keep the process reasonably close to setpoint.

REVIEW:
A “shorthand” symbol for an electronic amplifier is a triangle, the wide end signifying the input side and the narrow end signifying the output. Power supply lines are often omitted in the drawing for simplicity.
To facilitate true AC output from an amplifier, we can use what is called a split or dual power supply, with two DC voltage sources connected in series with the middle point grounded, giving a positive voltage to ground (+V) and a negative voltage to ground (-V). Split power supplies like this are frequently used in differential amplifier circuits.
Most amplifiers have one input and one output. Differential amplifiers have two inputs and one output, the output signal being proportional to the difference in signals between the two inputs.
The voltage output of a differential amplifier is determined by the following equation: Vout = AV(Vnoninv – Vinv)more details on the basics of opamp at ./
Opamp for every one famous design reference from TI
ANALOG UNIVERSITY from national semiconductor
Research groups in analog and mixed signal design
Analog Electronics ece.gatech.edu
analog ics from analogzone analogzone.com
CMOS Analog Filter Design from toronto.edu
ALL SPICE STUFF Page
Advanced Analog Circuit Design Techniques Course material from http://amesp02.tamu.edu
Circuit Diagrams,Design Notes
Design and Simulation of Operational Amplifier
Analog IC Design Software
Analog Office from Applied Wave Research
Mentor Graphics www.mentor.com
Tanner Tools www.tanner.com
RF Design Environment from agilent
XicTools IC Layout, DRC, LVS, and extraction software
Stabie-Soft IC Layout, DRC, LVS software
Magic The original layout editor. Free!
LASI free layout editor for windows
WinVLSI free layout editor tool for windows

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1. analog design

Operational amplifier: The ideal op amp is an amplifier with infinite input impedance, infinite open-loop gain, zero output impedance, infinite bandwidth, and zero noise. It has positive and negative inputs which allow circuits that use feedback to achieve a wide range of functions.
Using op amps, it’s easy to make amplifiers, comparators, log amps, filters, oscillators, data converters, level translators, references, and more. Mathematical functions like addition, subtraction, multiplication, and integration can be easily accomplished.

Practical, real-world op amps have finite characteristics but in most applications, are close enough to the ideal to make a huge range of inexpensive, high-performance analog applications possible. They are the building block for analog design.

One key to op amp design is nodal analysis. Since the input impedance is infinite, the current in and out of the + and – input nodes defines the circuit’s behavior.

• Brenda

This circuit is sliimar to the BBE Boosta Grande which also uses the TL071 opamp. But the Boosta Grande rolls off the highs as the volume is turned up. Does this circuit do the same thing? If so, can a component be substituted to stop the high freq rolloff?

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