The values of
the amplification Kp
and Kn
correspond to the amplifica-
tions at the most
positive and most negative values of
ec, respectively.
Equation
15 is valid as long as K is approximately a linear
function of ec.
Higher-order components
of harmonic distortion are present when
a plot
of K vs ec
gives a curved line. The amplitudes
of these components may
be calculated with the
help of Fourier analysis techniques and
the small-
signal amplifications
at several points.
Example 5. If
the input, voltage es
is 8 volts peak to peak and the
tube is biased at Ec
= -4 volts, then from Case I Example 4,
the distor-
tion is approximately 6%.
For a peak-to-peak signal of 4 volts, the
distortion is 3%, showing
that the distortion decreases as the input
signal is decreased.
POWER DISSIPATION IN THE TRIODE TUBE
Maximum plate power
dissipation in an R-C amplifier occurs when the
plate voltage is one-half
the voltage at which the load line intersects
the line of zero plate current.
In Fig.3-2 maximum plate dissipation
Fig. 3-2. Load
lines for power dissipation.
NOTE. if RL and RLD
coincide, Ebb = Ebz.
occurs when plate voltage
eb is one-half supply voltage Ebb
for the am-
plifier, with negligible
coupled loading; or, half the voltage at which
the dynamic load line cuts
the line of zero plate current when
the
coupled loading
reduces the dynamic load impedance to
RLD. The
maximum plate power dissipation
can be calculated from the equation:
Ppm = 0.5 Ebz* Ibm (16)
where Ebz
is the plate voltage at the intersection of the dynamic load
13
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Copyright 2008 for Phyllis
K. Pullen, M.D.,
by Robert J. Legg