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The main disadvantage of this coupling method is that it causes some loss for the low frequency signals. However, for amplifying signals of frequencies greater than 10 Hz, this coupling is the best and least expensive method. It is usually applied in small signal amplifiers, such as in record players, tape recorders, radio receivers, etc.
A direct-coupled amplifier [1] or DC amplifier is a type of amplifier in which the output of one stage of the amplifier is coupled to the input of the next stage in such a way as to permit signals with zero frequency, also referred to as direct current, to pass from input to output. This is an application of the more general direct coupling.
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 .
Amplifiers are sometimes classified by the coupling method of the signal at the input, output, or between stages. Different types of these include: Resistive-capacitive (RC) coupled amplifier, using a network of resistors and capacitors By design these amplifiers cannot amplify DC signals as the capacitors block the DC component of the input ...
Transformer coupling is an alternative AC coupling. Like RC coupling, it isolates DC between stages. However, transformers are bulkier and much more expensive than capacitors so is used less often. Transformer coupling comes into its own in tuned amplifiers. The inductance of the transformer windings serves as the inductor of an LC tuned circuit.
Conventional vacuum tube amplifier designs rely upon an output transformer to couple the amplifier's output stage to the loudspeaker. Instead, OTLs use one of two primary methods for output stage coupling: direct coupling (DC) or capacitive coupling (AC).
Capacitive coupling is the transfer of energy within an electrical network or between distant networks by means of displacement current between circuit(s) nodes, induced by the electric field. This coupling can have an intentional or accidental effect. Capacitive coupling from high-voltage power lines can light a lamp continuously at low intensity.
Designs frequently use a coupling greater than this (over-coupling) in order to achieve an even wider bandwidth at the expense of a small loss of gain in the centre of the passband. Cascading multiple stages of double-tuned amplifiers results in a reduction of the bandwidth of the overall amplifier. Two stages of double-tuned amplifier have 80% ...