Care must be taken when handling MOSFET transistors and devices.įigure 3. The layer of insulation is so thin that it can easily be damaged by static electricity. The difference is that the MOSFET has a very thin film of insulation (silicon dioxide) between the gate and the channel area. The MOSFET is similar in construction to the JFET. It is used extensively in digital circuits and memory circuits in computers. MOSFET ConstructionĪnother type of FET is the MOSFET. The amount of voltage applied to the gate will determine the current value from the source to the drain. Notice how the potential applied at the gate pinches off the flow of electrical energy.įigure 2. If a large potential is applied to the gate, a small current will exist in the channel between the source and the drain. If a small potential is applied to the gate, a large current through the P channel will exist. The current through the device is controlled by the gate potential. The physical construction of typical JFETs and their schematic symbols. The channel through the center of the device can be P- or N-type material.įigure 1. The channel is a path from the source to the drain. The gate is diffused into the channel material. These three parts are similar to the three main parts of a typical bipolar transistor. The three main parts of the JFET are the source, drain, and gate. The construction and symbols for the JFET are shown in Figure 1. There are two types of FETs, the junction field-effect transistor (JFET) and the metal oxide semiconductor field-effect transistor (MOSFET). A FET controls current in the source-drain circuit by the amount of potential applied to the gate. This is achieved by using novel circuits (on which patents are pending) which automatically and instantly protect the amplifier.The current through the collector-emitter circuit of a BJT is controlled by the amount of current in the base-emitter circuit. There are no circuit breakers, speaker fuses, or other resettable devices to impede the use of the Stereo 120 under any reasonable conditions of use or abuse. Thus it can be connected to source and speaker components and used with confidence in all conventional arrangements. The unit contains two 60 watt amplifiers on one chassis with a common power supply.Īlthough the Stereo 120 is a solid state device, containing transistors and similar semiconductors, it has been designed to be used under normal conditions without special safety precautions, just as if it were a high grade tube amplifier. The Dynaco Stereo 120 is an all silicon transistor basic power amplifier for use with separate preamplifiers such as the Dynaco PAT-4 or PAT-5, or for use with tape recorders or tuners such as the FM-5 or AF-6, which have their own volume controls. The RCA jacks and posts have also been upgraded which turns this amp into an absolute savage vintage beast. The circuits are clean, the cage has only a few minor dents or scratches and the caps and transistors sound amazing and strong on both channels. This is an outstanding amplifier from the late 1960's with a very nice patina and it sounds absolutely fantastic. The modifications Frank does bring this already spectacular solid state amp more into the tube tonality with his Mos-Fet circuitry. This is a beautiful condition Frank Van Alstine modded Dynaco 120a which he re-named the Mos-Fet 120b at Jensen's Stereo Shop in Burnsville, MN.
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