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correspondingly with the changes in grid voltage, the points Β and C
marking the limits of'the swing of both. The current, swinging
between 1\ and 4mA, is reduced by lfmA on the negative half-cycle
and increased by the same amount on the positive one. The whole is
therefore equivalent to the original steady current with an
alternating current of l}mA peak superposed on it. Incidentally this,
divided by the peak grid voltage, 0.5, gives 3.5 mA/V, the g
m
.
There are two ways in which this a.c. in the anode circuit can be
usefully employed. It can be used for producing an alternating
voltage, by passing it through an impedance. If the voltag ...