where, VTH and VTL are the high and low threshold voltages,
respectively. The frequency of the square wave (VSQ), and
hence the triangular wave (VTR), is controlled by the charge
and discharge time periods of the capacitor C1. By analyzing
the proposed circuit, the time period (T 1=f ; where f is the
frequency) is derived as a function of the circuit elements.
Our derivation leads to the following formula:
T 1
f
2C1RX ln 2R1
RX
2 1
:
3
This result shows that the frequency of the oscillator can
be adjusted only through C1 and R1 which are grounded
elements. This gives the circuit the advantage of replacing
R1 with a JFET to control the frequency via an external
voltage. Also, grounded capacitors are desirable for a fabrication
in an IC form.
The square wave output is fed to the y-terminal of the
integrator to avoid any loading effect [7] (i.e. the current