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The first discrete-transistor audio amplifiers barely supplied a few hundred milliwatts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved. [94] Modern transistor audio amplifiers of up to a few hundred watts are common and relatively inexpensive.
A FET amplifier is an amplifier that uses one or more field-effect transistors (FETs). The most common type of FET amplifier is the MOSFET amplifier , which uses metal–oxide–semiconductor FETs (MOSFETs).
If the output is taken as a voltage, the amplifier is a transresistance amplifier and delivers a voltage dependent on the load impedance, for example v out = i in R L for a resistor load R L much smaller in value than the amplifier output resistance R out. That is, the voltage gain in this case (explained in more detail below) is
In this example, the signal enters the gate, and exits the drain. The only terminal remaining is the source. This is a common-source FET circuit. The analogous bipolar junction transistor circuit may be viewed as a transconductance amplifier or as a voltage amplifier. (See classification of amplifiers). As a transconductance amplifier, the ...
In this circuit, the base terminal of the transistor serves as the input, the collector is the output, and the emitter is common to both (for example, it may be tied to ground reference or a power supply rail), hence its name. The analogous FET circuit is the common-source amplifier, and the analogous tube circuit is the common-cathode amplifier.
Figure 2: A negative-feedback amplifier. The circuit can be explained by viewing the transistor as being under the control of negative feedback.From this viewpoint, a common-collector stage (Fig. 1) is an amplifier with full series negative feedback.
LDMOS (laterally-diffused metal-oxide semiconductor) [1] is a planar double-diffused MOSFET (metal–oxide–semiconductor field-effect transistor) used in amplifiers, including microwave power amplifiers, RF power amplifiers and audio power amplifiers. These transistors are often fabricated on p/p + silicon epitaxial layers.
The first transistor hi-fi system was developed by engineers at GE and demonstrated at the University of Philadelphia in 1955. [9] In terms of commercial production, The Fisher TR-1 was the first "all transistor" preamplifier, which became available mid-1956. [10] In 1961, a company named Transis-tronics released a solid-state amplifier, the ...