Sawtooth Wave Generator – Understand it Clearly

You can consider a sawtooth waveform (also called a saw wave) a non-sinusoidal wave type. Its name comes from its similarity with a plain-toothed saw with zero rake angle. A sawtooth waveform typically ramps up and later drops sharply. The inverse (reverse) case ramps downward and immediately rises sharply. That said, you can consider it an asymmetric triangular wave.  

This article will discuss how to use a sawtooth wave generator. Also, we'll touch on its various configurations and mention a few areas where you can apply them.

What is a Sawtooth Wave Generator?

Fig 1: A Sawtooth Wave

Source: Wikicommons  

A sawtooth wave generator is an oscillator circuit that generates a sawtooth waveform. It's typically like the same circuit as the triangular waveform generating circuit. 

However, here you should replace the resistor always in series with a capacitor with two resistors. It would help to place each resistor in pairs with a diode that goes the opposite direction.

Different Configurations of a Sawtooth Wave Generator

Sawtooth Wave Generator using 555

Fig 2: 555 timer IC

Source: Wikicommons  

You can construct a sawtooth wave generator with a 555 timer IC & a transistor. The setup consists of a capacitor, a transistor, resistors, a Zener diode, and a reliable fixed current source.

Assuming that initially, we have a completely discharged capacitor, we’ll have zero voltage across the capacitor. Also, the 555's voltage will be high. Please internal comparators at pin 2.

Next, the capacitor begins to charge and supply voltage. It is due to the shorting of the 555's internal transistor to the ground, which makes it open. 

Fig 3: 555 Sawtooth Wave Generator Circuit

As the charging continues, the 555 output becomes low. It happens if there's a 2/3 increase in the voltage above the supplied voltage.

When discharging, the output from 555 will become high. It happens if there's a 1/3 decrease in the voltage below the supply voltage. It means that the capacitor discharges and charges between 1/3 and 2/3 of the supplied voltage.

That said, the main disadvantage of this is that you'll need a bipolar supply of power. You can calculate the resulting frequency using the formula below:

F = (1/(R*C*Vpp)) x (Vcc - 2.7), where:

• Vcc - Supply voltage
• Vpp - Peak to peak (P) output voltage

Sawtooth Wave Generator using OP-AMP

Fig 4: OP-AMP Sawtooth Wave Generator Circuit

Time-based generators and pulse width modulation setups use sawtooth waveforms. Next, you introduce a potentiometer as the wiper changes to the negative voltage (-V). The fall time becomes less than the rise time.

If the wiper changes to a positive voltage (+V), the rise time becomes lower than the fall time. The inverting terminal receives a negative voltage if the comparator output switches to negative saturation. 

As a result, the wiper switches to a negative supply. Therefore, the current via the resistor and capacitor goes down. More importantly, this results in a decrease in the voltage difference across R1.

In addition, the rise time and slope decrease. In contrast, the voltage difference increases if the comparator output is under positive saturation. Also, the current via the capacitor resistor increases.

It results from the availability of negative voltage in the inverting terminal. Next, the fall time goes down, and the slope increases. Consequently, the output becomes a sawtooth waveform.

These components are for making the circuit:

1. R1- 1K
2. Op-amp IC- 741c
3. R-47K
4. R2- 180Ω

Application of Sawtooth Wave Generator

Source: Pixabay

1. Music: In this case, you can use the sawtooth waveform to create sounds using analog music and subtractive virtual synthesizers.
2. Also, you can use them to create switched-mode power supplies.  happens by comparing the output feedback signal (in the regulator chip) to a sawtooth with high frequency. It generates a new duty PWM wave at the comparator's output.
3. It is the horizontal & vertical signal used to create raster on monitor screens or cathode ray tube (CRT) based televisions.
4. Oscilloscopes use it for horizontal deflection. However, they mostly apply electrostatic deflection.

Conclusion

In conclusion, this is all the info about the working principle of a sawtooth wave generator. As you have already seen, a sawtooth wave generator has different configurations. These include the 555 and the OP-AMP configured generators.

Also, they have several applications, the main one being in music. However, if you have any questions, feel free to contact us.