Category Archive for: MULTISTAGE AMPLIFIES

THE IDEAl DIFFERENTIAL AMPLIFIER

The principal feature that distinguishes a differential amplifier from the configuration is that a signal applied to one input of a differential amplifier induces a voltage with respect to ground on the amplifier’s other output. This fact will become clear in our study of the voltage and current relations in the amplifier the basic BJT version of II differential amplifier.…

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Mutual Inductance

Mutual inductance is a measure of the ability of one winding to induce a voltage in a second winding. Contrast this concept with that of self-inductance, which is a measure of the ability of a winding to induce a voltage in itself. Of course, in both cases, a voltage is induced only when current is changing with time.…

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Frequency Response

The output voltage of an ideal transformer is independent of frequency. However. in a real transformer. we must consider how the inductive components affect the output when frequency changes. because the reactances of those components increase with frequency. Furthermore, every transformer has capacitance between the turns of its wind.ugs, and capacitive reactance is also affected by frequency. Recall that capacitance…

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leakage Flux and Coupling Coefficients

One of the assumptions made for an ideal transformer is that all of the magnetic flux generated by one winding is coupled to the other winding. In fact. some of the flux generated by the primary winding of a practjeal transformer “escapes,” in the sense that it is not confined entirely to the core, and therefore does not…

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LIMITATIONS OF PRACTICAL TRANSFORMERS

Copper Losses As we know, all materials have electrical resistance, including the wire wrapped  the core of a transformer to form its primary and secondary windings. The resistance in these windings is responsible for an average power loss, PI> that can be calculated in the usual way: where R, and R. are the resistances of the primary and…

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A Bifet Amplifier

Bifet is a coined term meaning a combination of bipolar and FET, and a bifet amplifier is one that contains both types of transistors. These amplifiers arc designed to exploit the most desirable characteristics of each device, such as the very large input impedance of the FFT and ‘he large voltage gain of the 13JT. A good example is…

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TRANSISTOR ARRAYS

Multiple transistors sharing a common substrate are available in integrated-circuit packages called transistor arrays. Compared to medium- and large-scale integrated circuits, arrays contain relatively few devices, but they have the advantage that all or most device terminals are accessible at external pins. This accessibility allows the user to connect the components in a variety of ways and provides great…

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The Darlington Pair

When lite It,ilcctors 01 two OJ tied together and the ernittor of one is directcoupled to the base of the other, as shown in Figure 11-1 X, we obtain ct. imponant and highly usciul ~()l1figar;lI;ol ca!h.l; Darlington pair, The com hi nation is used ill amplitin circuits as if it were a single transistor having the base, collector,…

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Frequency Response of Cascaded Stages

In Chapter 10. we  i<:cussed the fact that the lower cutoff frequency of a single amplifier stage is influenced by as many as three different break I'<!qllencies. having v-ilues that depend on various RC components in the circuit. If the break frequencies were not close in value, VIe approxin., ~ d the actual lower cutoff frequency of the amplifier…

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MULTISTAGE AMPLIFIES

In many applications, a single amplifier cannot furnish all the gain that is required to drive a particular kind of load. For example. a speaker represents a hell load in an audio amplifier system, and several amplifier stages may be required to “boost” a signal originating at a microphone or magnetic tape head to a level ‘ufficient to provide…

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