Negative Resistance Amplifier

Negative Resistance Amplifier: The classical application of the tunnel diode was in microwave oscillators, especially after it was realized that the secret of stable oscillations lay in loosely coupling the diode to its tuned circuit. Other semiconductor devices have subsequently appeared, producing far more microwave power than the tunnel diode ever could. The tunnel diode […]

Parametric Amplifier Types

Parametric Amplifier Types: The basic Parametric Amplifier Types have already been discussed in detail, but several others also exist. They differ from one another in the variable reactance used, the bandwidth required and the output frequency (signal or idler). Various other char­acteristics of Parametric Amplifier Types must also now be discussed, such as practical circuits, […]

Parametric Amplifier

Parametric Amplifier: The parametric amplifier uses a device whose reactance is varied in such a manner that amplification results. It is low-noise because no resistance need be involved in the amplifying process. A varactor diode is now always used as the active element. Ampli­fication is obtained when the reactance (capacitive here) is varied electronically in […]

Varactor Diode Operation and Characteristics

Varactor Diode Operation and Characteristics: Varactor Diode Operation and Characteristics were first used in the early 1950s as simple voltage-variable capacitance and later for frequency modulation of oscillators. They thus represent a very mature semiconductor microwave art. As materials and construction improved, so did the maximum operating frequencies, until the stage has now been reached […]