voltage V+ = 222V in order to obtain Va = 200V on the anode. Now suppose we impress on the -1V bias voltage a signal of 1V peak-peak, so that the grid voltage varies between -.5V and -1.5V. When Vg=-.5V, the anode current will increase to 3.1mA, lowering the anode voltage to Va = V+ - 10000Ω × 3.1mA = 191V (orange curve). When Vg=-1.5V, the anode current will decrease to 1.4mA, raising the anode voltage to Va = V+ - 10000Ω × 1.4mA = 208V (green curve). Therefore a 1V peak-peak signal on the input (grid) causes an output voltage change of about 17V. Thus voltage amplification of the signal is obtained. The ratio of these two changes, the voltage amplification factor (or mu) is 17 in this case. It is also possible to use triodes as cathode followers in which there is no voltage amplification but a huge reduction in dynamic impedance; in other words, the current is greatly amplified (as it also is in the common-cathode configuration described above). Amplifying either the voltage or current results in power amplification, the general purpose of an amplifying tube (after all, either the current or voltage alone could be increased just using a transformer, a passive device). See also Hanso Idzerda List of vacuum tubes References External links — A French page on thermionic valves. Of particular interest is the 17-minute video showing the manual production of triodes. Triode valve tutorial Telecommunications-related introductions in 1906 Audiovisual introductions in 1906 Vacuum tubes de:Elektronenröhre#Triode it:Valvola termoionica#Triodo sv:Elektronrör#Trioden