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A typical example of the use of a common-emitter amplifier is shown in Figure 3. Figure 3: Single-ended npn common-emitter amplifier with emitter degeneration. The AC-coupled circuit acts as a level-shifter amplifier. Here, the base–emitter voltage drop is assumed to be 0.65 volts.
Nevertheless, this use is still relevant in the 21st century because tubes and tube amplifiers continue to be produced for niche markets. In analog telecommunications systems center-tapped transformers can be used to provide a DC path around an AC coupled amplifier for signalling purposes.
That is, an active load imposes less restriction on the output voltage swing. Notice that active load or not, large AC gain still is coupled to large AC output resistance, which leads to poor voltage division at the output except for large loads R L ≫ R out. For use as a current buffer, gain is not affected by R C, but output resistance is.
Circuit diagram of a ladder network low-pass filter: a two-element-kind network Comprehensive cataloguing of network graphs as they apply to electrical circuits began with Percy MacMahon in 1891 (with an engineer-friendly article in The Electrician in 1892) who limited his survey to series and parallel combinations.
The direct-coupled amplifier was influential in the development of Fairchild's uA709 operational amplifier by Bob Widlar, which Noyce knew about as he was one of the founders of Fairchild Semiconductors. The direct-coupled amplifier is also the basis for Philco's Mark I hearing aid, which used the circuit built with silicon alloy transistors.
In electronics, electric power and telecommunication, coupling is the transfer of electrical energy from one circuit to another, or between parts of a circuit. Coupling can be deliberate as part of the function of the circuit, or it may be undesirable, for instance due to coupling to stray fields .
It is a way of interconnecting two circuits such that, in addition to transferring the AC signal (or information), the first circuit also provides DC bias to the second. Thus, DC blocking capacitors are not used or needed to interconnect the circuits. Conductive coupling passes the full spectrum of frequencies including direct current.
Operational amplifiers (op-amps) are commonly employed to carry out the amplification of the signal in the signal conditioning stage. In some transducers , signal conditioning is integrated with the sensor, for example in Hall effect sensors .