Basic Radio is a free introductory textbook on electronics based on tubes. See the editorial for more information.... 
Home Oscillators ConstantCurrent Systems  
Search the VIAS Library  Index  
ConstantCurrent SystemsAuthor: J.B. Hoag
There are certain applications which require the current to remain constant despite changes in the resistance of the load. The voltage may go up or down, but the current must be constant. This is the case with the power supply of highpowered oscillators, and with certain applications of arc lamps.
Figure 29 L shows circuits whereby a constantvoltage system may be transformed into a constantcurrent system. The reactances of the inductance L and of the capacitance C are made equal to each other at the supply frequency, i.e., 2πfL = 1/2πfC. When the output resistance R is small, the voltage across it decreases, but the current through it remains constant, and vice versa. A shortcircuited load is not dangerous but an open circuit will develop high voltage, and perhaps puncture C. The constancy of the current is vitiated somewhat by the fact that the coil has resistance as well as inductance and by the fact that its inductance changes slightly when different currents pass through it.


Home Oscillators ConstantCurrent Systems 