Radio Frequency Integrated Circuit Design - Webs

340 Radio Frequency Integrated Circuit Design
Figure 9.13 A resonator without damping, which oscillates if there is enough current.
Figure 9.14 A resonator with feedback to control the current.
quiescent point so that they are operating almost in Class B mode. Note that
this is essentially the same circuit as the automatic amplitude control for the
VCO previously discussed. The only difference is that here the transistors are
biased so that they turn on as soon as there is any swing, rather than waiting
until it reaches some fraction of a V BE. When they turn on, they provide a
full wave rectified current around the loop to the current mirror. This feedback
loop controls the current so that the oscillator just starts, which means the
negative g m circuitry perfectly cancels the resonator and circuit losses. As before,