Page 203 - Build Your Own Transistor Radios a Hobbyists Guide to High-Performance and Low-Powered Radio Circuits

FIGURE 13-4 A current-driven LRC circuit.
Many active devices have current-source outputs such as a bipolar transistor with a
collector terminal or a field-effect transistor with a drain terminal. The concept of a

current source may not be familiar to some people because a voltage source is
more easily visualized as a battery or a signal generator. In an ideal voltage source,
the generated signal delivers a voltage signal independent of the current flowing
into or out of the voltage source. In an ideal current source however, the generated
current is independent of the voltage across the ideal current source.

One-Transistor Oscillator
Figure 13-5 shows an oscillator system with a voltage-dependent current source.

The current source is controlled by the amount of voltage applied to the input of
the system. Signal current is fed to a parallel Le circuit where two capacitors form a
voltage divider network.