This circuit produces low frequency sine wave signals. The range is up to some hundreds quilohertz and and any NPN or PNP general purpose transistor can be used in the basic configuration. The following formula is used to calculate the frequency:

**Formula 1 **

Frequency:

f = 1 / (4.88 x π x R x C)

Where: f is the frequency in hertz (Hz)

π is the constant 3.1416

R is the resistance in ohm (Ω)

C is the capacitance in farads (F)

Note: 4.88 = 2 x ?6

**Application example: **

Determine the running frequency of the circuit shown in figure bellow.

** Data: **

C = 10 nF = 0.01 µF

R = 20 kΩ

f = ?

**Applying formula 1:**

f = 1 / (4.88 x 3.14 x 20 x 10^{3} x 0.01 x 10^{-6})

f = 10^{3} / 3.06

f = 326.8 Hz