Engineering Dictionary
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Transistor Circuit Schematics
This page lists a few transistor circuits not found on other pages because no topic exists. However the circuits do serve to make some specific point, but do not come with a description.
RF Transistor Circuit
An example of an RF amplifier circuit using a transistor is shown below. The transistor is identified as TUT which stands for Transistor Under Test. The point of the schematic is to show the additional components required in an RF circuit. Also note that the case of the transistor is grounded and there appears to be metal shield being used on the printed wiring board. Although there is no clear-cut definition of what the dashed grounded lines means. Many transistor cases have an un-committed metal case or tab that may be used for either grounding or heat dissipation. Note that C5 is a Feed-through Capacitor used to suppress EMI between inter-panel connections.
RF Transistor Under Test
The next circuit example below is also an RF circuit. In this case the transistor is labeled as DUT for Device Under Test, because the circuit is a setup to test operating characteristics of the transistor. Note the heavy use of variable capacitors, or trimmer capacitors normally implying an RF circuit. Coaxial connectors are shown as 50 ohm inputs and outputs, depicted by the cycle around the dot.
Device Under Test, Power
The next circuit is also another RF circuit except this time it depicts an actual VHF transistor amplifier. The difference here is the shielded screen around the transistor case, and the switchable inductors [which are ganged together].
VHF Transistor Amplifier
This next circuit is another RF FET amplifier. This particular example uses a four lead package with the fourth lead being connected to the transistor case, which is than grounded. Again 50 coax connectors are shown.
FET VHF Amplifier
Positive Output Swing
Emitter Follower Transistor Amplifier, NPN. Positive Output swing.
Design Note; The bias resistors will change value depending on the application.
