Simple VCO

Y5V properties

The simple VCO design is based on properties of Y5V capacitor dielectric material.

Transistors T1 and T2 form emiter coupled oscillator.

The paralell LC network sets the oscillation frequency.

The C capacitor consists of two capacitors connected in series.

T3 is a emmiter follower for driving the speaker.

The circuit illustrates the effect of C(U) and C(T) dependency of Y5V dielectric material (figure below).

Try to build it yourself ! 

Pictures:
Y5V properties