Ideal constant –
current source is that voltage source whose internal resistance is infinity. In
practice, it is approached by a source which possesses a very high resistance
as compared to that of the external load resistance.
As shown in
figure 2 above, let the 6V battery voltage source have an internal resistance
of 1MΩ and let the load resistance vary from 20k to 200k. The current supplied
by the source varies from 6/1.02 = 5.9µA to
figure 2 above, let the 6V battery voltage source have an internal resistance
of 1MΩ and let the load resistance vary from 20k to 200k. The current supplied
by the source varies from 6/1.02 = 5.9µA to
6/1.2 = 5µA. As
seen, even when the load resistance increases 10 times, current decreases bu
0.9µA. Hence, the source can be considered for all practical purposes, to be a
constant – current source.
seen, even when the load resistance increases 10 times, current decreases bu
0.9µA. Hence, the source can be considered for all practical purposes, to be a
constant – current source.
