The relaxation circuit shown in figure 1 using an operational amplifier can produce signals from very low frequencies (under 1 Hz) up to 100 kHz according the used Op. Amp. The output is a square wave but in the junction between R and C the signal is sawtooth wave.

 


 

 

 

Formula 1

Square Wave Oscillator:

f = 1 / (6 x R x C)

 

 

Where:

f is the frequency in hertz (Hz)

R is the resistance in ohm (Ω)

C is the capacitance in farads (F)

 

Application example:

Determine C to a frequency of 10 kHz given R = 10 kΩ. The circuit is shown in figure 2.

 

 

Figure 2 – The circuit
Figure 2 – The circuit

 

 

Data:

f = 10 kHz

R = 10 kΩ

C = ?

 

 

Using formula 1:

10 x 103 = 1 / (6 x 10 x 103 x C)

 

Isolating C:

C = 1 / (6 x 10 x 103 x 10 x 103)

C = 1 / (600 x 106)

C = (1 / 600) x 10-6

C = 0.0016 µF

C = 1.6 nF

 

 

 

 

Datasheets


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