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Square Waves Produced by Blocking Action

Author: J.B. Hoag

In Fig. 30 D, the 110-volt, 60-cycle current is rectified by the 6H6 tube and develops a direct pulsating voltage across R1. The 6SJ7 tube operates with zero bias. The strong negative pulses from R1 drive its plate current to zero, i.e., block the tube. The resultant voltage changes across R2 are of reasonably square wave-form. With a large time constant RC in the output circuit, this wave-form appears across the output terminals. R can be 100,000 ohms and C can be 4 fd., as in Fig. 30 A. Obviously both of the square-wave generators just described can be operated at other than 60 cycles by suitable changes in the various circuit constants.

Fig. 30 D. A circuit for changing 60-cycle sine waves into 60-cycle square waves by blocking action. Sharp pulses will be obtained if the time constant RC is made very small

Last Update: 2009-11-01