Search results
Results from the WOW.Com Content Network
The only terminal remaining is the source. This is a common-source FET circuit. The analogous bipolar junction transistor circuit may be viewed as a transconductance amplifier or as a voltage amplifier. (See classification of amplifiers). As a transconductance amplifier, the input voltage is seen as modulating the current going to the load.
Because the amplifier input resistance is small, the driver delivers by current division a current v Thév / R S to the amplifier. The current gain is unity, so the same current is delivered to the output load R L, producing by Ohm's law an output voltage v out = v Thév R L / R S, that is, the first form of the voltage gain above.
It has two radio frequency amplifier stages, one grid-leak detector/amplifier and three class ‘A’ audio amplifier stages. There are 3 tuned circuits T1-C1, T2-C2, and T3-C3 . The second and third tuning capacitors, C2 and C3 , are ganged together (indicated by line linking them) and controlled by a single knob, to simplify tuning.
Hobbyist constructed Mono PPP amplifier using 813/QB2/250. ~ 65W in Class A. Weight is 48 kg, dissipation is 1 kW. Many modern commercial amplifiers (and some hobbyist constructions) place multiple pairs of output valves of readily obtainable types in parallel to increase power, operating from the same voltage required by a single pair.
When driven by a line output's usual low impedance of 100 to 600 ohms, this forms a "bridging" connection in which most of the voltage generated by the source (the output) is dropped across the load (the input), and minimal current flows due to the load's relatively high impedance.
Figure 2: A negative-feedback amplifier. The circuit can be explained by viewing the transistor as being under the control of negative feedback.From this viewpoint, a common-collector stage (Fig. 1) is an amplifier with full series negative feedback.
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
A FET amplifier is an amplifier that uses one or more field-effect transistors ... 1957, Diagram of one of the SiO2 transistor devices made by Frosch and Derrick [6]