Semiconductor Microwave Devices

Gunn Effect

Gunn Effect: In 1963, Gunn discovered the transferred electron effect which now bears his name. This Gunn Effect is instrumental in the generation of microwave oscillations in bulk semicon­ductor materials. The effect was found by Gunn to be exhibited by gallium arsenide and indium phosphide, but cadmium telluride and indium arsenide have also subse­quently been […]

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Tunnel Diode Applications

Tunnel Diode Applications: In all its Tunnel Diode Applications, the tunnel diode should be loosely coupled to its tuned circuit. With lumped components, this is done by means of a capacitive divider, with the diode connected to a tapping point, while the divider is across the tuned circuit itself. In a cavity, the diode is

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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

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Tunnel Diode Equivalent Circuit

Tunnel Diode Equivalent Circuit: The Tunnel Diode Equivalent Circuit, when biased in the negative-resistance region, is shown in Figure 12-18. At all except the highest frequencies, the series resistance and inductance can be ignored. The resulting diode equivalent circuit is thus reduced to the parallel combination of the junction capacitance Cj and the negative resistance

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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,

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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

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Frequency Multiplier Circuit

Frequency Multiplier Circuit: A typical Frequency Multiplier Circuit chain is shown in Figure 12-11, The first stage is a transistor crystal oscillator, operating in the VHF region, and this is the only circuit in the chain to which dc power is applied. The next stage is a step-recovery multiplier by 10, bringing the output into

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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

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Microwave Transistors

Microwave Transistors: Silicon bipolar transistors were first on the microwave scene, followed by GaAs field-effect transistors. Indeed, FETs now have noticeably lower noise figures, and in the C band and above they yield noticeably higher powers. A description of Microwave Transistors constructions and a discussion of their performance now follow. Transistor Construction: The various factors

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High Frequency Limitations

High Frequency Limitations: As stated, transistors suffer from High Frequency Limitations. These are of a twofold nature. On the one hand, there are the same difficulties as those encountered with tubes, On the other hand, there is some difficulty in specifying accurately the performance of microwave transistors in a manner which would make it relatively

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