(1) Stability depends on several
circuit. The higher the Q of
the tank circuit the better
Bias stability is attained by
conjunction with R1 and C1.
Resistor R1 and capacitor C1
action is identical with that
biasing of an electron-tube
bias, base-leak bias builds
up and adjusts itself to
(2) Since an LC tank insures a
operate Class C.
operation is preferred for
its higher efficiency.
(3) Modified versions of this type may have the tuning tank placed in the
b. Hartley. As in the case for electron-tube oscillators, the dc power supplied
can be series fed or shunt fed. Recall that a series feed passes dc through the
tank circuit, whereas a shunt feed does not. The tickler circuit shown in figure
2-5 is series fed.
shunt fed; note that no dc is applied to the tank circuit.
The RF choke (RFC)
blocks the signal from the power supply.
Capacitor CO blocks dc and effectively
passes RF. Either series or shunt feed can be used for LC oscillators.
that shown in B of figure 2-6.
Capacitors CO, CB (for biasing), and
bypass CE are effective RF shorts.
The tank circuit is common to the
connection made to the tank's inductance. When a single coil is tapped,
from collector (point c) to base (point b) can be explained by the fact
that the signals at opposite ends of the coil are 180 out of phase with
reference to the emitter (point e).
necessary. The tank inductance can be made up of two separate coils, one
in the base circuit (b and e) and the other in the collector circuit (c to