Category Archive for: Applications of Operational Amplifiers

Active Filter Design

The analysis of active filters requires.complex mathematical methods that are beyond  scope of this book. We will therefore concentrate on practical design methods that will allow us to construct Butterworth and Chebyshev filters of various types and orders. The discussion that follows is based on design procedures using tables that can be found in Rapid l’ractical Designs of Active…

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The Colpitts Oscillator

In the Colpitts oscillator, the impedance in the feedback circuit is a resonant LC . network. See Figure 14-46(a). The frequency of oscillation is the resonant frequency of the network, which is the frequency at which the phase shift through the network is 180°. At th~t frequency, the impedance is a real number.The feedback network. The impedance…

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The RC Phase-Shift Oscillator

One of the simplest kinds of oscillators incorporating an operational amplifier can be constructed as shown in Figure 14-42. Here we see that the amplifier is COt” ‘ctl”:;3 in an inverting configuration and drives three cascaded (high-pass) RC sections.The arrungcmcnt is called an RC phase-shift oscillator. The inverting amplifier causes a umo phase shift in the signal passing…

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OSCILLATORS

An oscillator is a device that generates a periodic, ac output signal without any form of input signal required. TIle term is generally used in the context of a sine-wave signal generator, while a square-wave generator is usually called a multioibrator. A function generator is a laboratory instrument that a user can set to produce sine, square, or triangular…

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INSTRUMENTATION AMPLIFIERS

In Section 14-1 we saw how an amplifier can be operated in a differential mode to produce an output voltage proportional to the difference between two input signals (see Figure 14-5). Differential operation is a common requirement in instrumentation systems and other signal-processing applications where high accuracy is important. The circuit of Figure 14-5 has certain limitations in these…

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Waveshaping

Waveshaping is the process of altering the shape of a waveform in some prescribed manner to produce a new waveform having a desired shape. Examples include altering a triangular wave to produce a square wave, and vice versa, altering a square wave to produce a series of narrow pulses, altering a square or triangular wave to produce a sine…

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Practical Differentiators

From a practical standpoint, the principal difficulty with the differcntiator is that it effectively amplifies an input in direct proportion to its frequency amiiereforc i””Il:ases the level of high-frequency noise in the output. Unlike the integrator, which “smooths” a signal by reducing the amplitude of high-frequency components, the differentiator intensifies the contamination of a signal by high-frequency noise. For…

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Current-Controlled Voltage Sources

An ideal current-controlled voltage source has an output voltage that (1) is equal to a constant (k) times the magnitude of an independent current: Vo = kl., and (2) is independent of the load connected to it. Here, the constant k has the units of ohms. A current-controlled voltage source can be thought of as a current-to-voltage converter, since…

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INTEGRATION,DIFFERENTIATION,AND WAVESHAPING

Electronic Integration An electronic integrator is a device that produces an output waveform whose value at any instant of time equals the total area under the input waveform up to that point in time. (For those familiar with mathematical integration, the process produces the time-varying function I:, Vi,,(/) dt.) To illustrate this concept, suppose the input to an electronic…

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CONTROLLED VOLTAGE AND CURRENT SOURCES

Recall that a controlled source is one whose output voltage or current is determined by the magnitude of another, independent voltage or current. We have used controlled sources ex~ensively in our study of transistor-circuit models, but those were, in a sense, fictitious devices that served mainly to simplify the circuit analysis. We wish now to explore various techniques that…

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