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 semiconÂductor materials. The effect was found by…
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…
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.…
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…
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…
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…
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…
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 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…
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,…