Physics. — ''Tlie audion ai< (in dinpUjier." By G. Holst and E. 

 OosTERHUis. (Coiïimunicated by Prof. H. A. Lorentz.) 



(Communicated in the meeting of October 26, 1918). 



Im a recently published article G. Vallauki ') communicated some 

 calculations about the audion as an amplifier. He points out, that 

 under normal conditions, one may appro,\iuiately i-epresent the anode 

 current of the audion 1 as a lineair function of the grid potential 

 V and the plate potential V -. 



I ^iz av -\- 1>V -\- c. 



if in the plate circuit a resistance R is placed, it may be easily 

 calculated that the variations of the current 1^ in the [)late circuit 

 depend upon the variations v^ of the grid potential in the following 

 way: 



a 



1 -f bR 



Now Vallauri takes the ratio — as a measure for the amplification. 



It appears to us that more satisfactory results are obtained, if we 



^. . • . 



do not assume — as the amplification, but the dimensionless ratio 



of the potential variations on the resistance R to the variations of 



aR 



the grid potential. The amplification then becomes 0= — and 



^ ^ ' I -\- bR 



a 

 for large values of R : G,nax = =' 



b 



If instead of a resistance a selfinduction L is placed in the anode 



circuit, we get, if the frequency of the grid variations is n: 



variation potential on selfinduction 2jr n La 



G = 



variation grid potential V \ -\ A:t* Ji* b* L^ ' 



a 

 and for large values of L: Gmax = —• 



b 



In the case of a capacity C connected in parallel to the self- 

 induction L we obtain : 



1) Nuovo Cimenlo (13) 169, 1917. 



