. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. BEAM TETRODE for electrons knocked out of the anode to do anything but fall back on to it again. With the pentode the anode characteristic is as in Figure and voltage amplifiers may be designed graphically in the same manner as for triodes (Figure ). Since at the bottom of the diagram the curves tend to close up, the bottom edge of the working region is bounded by an arbitrary level at which the cramping becomes intolerable. The left-hand edge is bounded by a voltage just above th
. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. BEAM TETRODE for electrons knocked out of the anode to do anything but fall back on to it again. With the pentode the anode characteristic is as in Figure and voltage amplifiers may be designed graphically in the same manner as for triodes (Figure ). Since at the bottom of the diagram the curves tend to close up, the bottom edge of the working region is bounded by an arbitrary level at which the cramping becomes intolerable. The left-hand edge is bounded by a voltage just above the knee voltage. The remainder of the working region is bounded by the hyperbola of maximum anode dissipation, and by the maximum permissible anode voltage and current, as in the triode. The amplification may be taken as g^R and is typically 150 times. Pentodes may also be used for power amplification, and will deliver more power for a given mean anode voltage and current than will a triode, as explained in Figure Due to the cramping of the curves at the bottom, pentodes, Triode power rectangle Triode characteristic. Pentode characteristic Figure whether high-level voltage or power-amplifying, tend to cause more dis- tortion than triodes. The optimum load for power pentodes is only about 1/5 to 1/10 of r^; but as ;•„ is so high, of the order of hundreds of thousands of ohms, the optimum load usually works out higher than for a triode. BEAM TETRODE A beam tetrode is a carefully made—and therefore expensive—valve suitable only for power ampHfication {Figure ). The screen grid is wound in the shadow of the control grid (as illuminated by the cathode) as a result of which there is a clear run for the 'beaming' of electrons on to the anode, and incidentally the screen current is extremely small. 'Beam forming plates' at cathode potential are included which constrain the beam to strike the anode at right angles. Tetrode kink is prevented because: (1) secondary e
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