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Design Example - Cathode Follower

Assume that tubes 828 and 849 in Fig. 157 operate at EB = 1,700 volts. With Ec = -75 and 700 watts output, 849 plate swing is 1,200, Emin = 500, peak grid voltage = +105, and peak grid current is 0.090 amp. This is peak load for the 828 tube which can operate class AB1. The 828 tube plate swing is 1,200 + 180 = 1,380, or Emin = 1,700 - 1,380 = 320 volts, and the 828 peak load is 105/0.090 = 1,170 ohms. The cathode choke of 828 and the grid chokes and capacitors of 849 should have 1.41 · 1,170 = 1,650 ohms reactance for 100 per cent modulation at frequency f1. At 10 cycles this would be 27 henrys. Peak voltage across these chokes is the 828 plate swing.



Last Update: 2011-01-24