| Electrical Communication is a free textbook on the basics of communication technology. See the editorial for more information.... |
|
Home  Electronic Applications in Communication High-Vacuum Thermionic Five- Electrode Tubes |
|
 Search the VIAS Library | Index
|
  |
High-Vacuum Thermionic Five-Electrode TubesIn the five-electrode tube, or pentode, developed about 1930, a suppressor grid is placed between the screen grid and the plate. The suppressor grid is usually directly connected to the cathode. The control grid and the screen grid function as previously explained. The secondary electrons from the plate cannot flow to the screen grid, because to do this they would have to flow through the suppressor grid which is at the potential of the cathode and the cathode is negative with respect to the plate. The so-called suppressor grid does not suppress secondary emission but merely forces the secondary electrons back to the plate. There is even less tendency for feedback than with the screen-grid tetrode, and hence the pentode is a superior radio-frequency voltage amplifier. The additional shielding increases both the amplification factor and the plate resistance, typical values being μ = 1000 and rp = 1,500,000 ohms.
|
|
| Home Electronic Applications in Communication High-Vacuum Thermionic Five- Electrode Tubes |
|
Last Update: 2011-05-30