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# Problems

Author: E.E. Kimberly

 Problem Answer 1 Calculate the ripple voltage amplitude of a half-wave rectifier with a load resistor of R = 5000 ohms in parallel with a condenser of C = 100 mfd. The frequency of supply is 20 cycles. Use the simplifying assumptions relating to wave form. 2 Calculate the amplification factor of the 6C5 triode whose plate characteristics are shown in Fig. 27-11. 3 What is the average direct voltage across the load in the accompanying circuit? Assume that the tubes are perfect rectifiers. 4 In the accompanying circuit it is necessary to make the gas tube fire by increasing the light on the phototube from 0 to 0.03 lumen. Assume that the gas tube fires when its grid is at zero volts. What must be the value of Rg to just fire .the gas tube? Use the characteristic curves of Fig. 27-45 for a vacuum-type phototube. 5 The following data are found in the tube manual for the triode in the accompanying circuit: Plate voltage 250 v. Heater current 0.3 amp Grid bias -20 v. Amplification factor 8 Plate resistance 1700 ohms Transconductance (gm) 4700 micromhos Heater voltage 6.3 v. Plate current 40 ma. Find the values of EM and Ece to give the specified operating conditions. Find the effective value of alternating voltage across L. Find the total power input to the triode with zero a-c grid voltage. 6 Assume that the thyratron in the accompanying circuit fires when the grid voltage is zero, and that there is no tube drop. If C = 1 microfarad and R = 5000 ohms, at what angle will the triode fire? If R is adjusted so that the thyratron fires at 45 deg, what is the average current through R^l 7 In the accompanying circuit is shown a 6C5 triode connected as an amplifier. Ecc= - 8, RL = 50,000, and Ebb=300. Draw the load line and determine the d-c component of the plate current. What are the maximum and minimum voltages across RL, if ea is a sine wave with an amplitude of 2 volts? Find rp for this operating point.

Last Update: 2011-02-23