The term “Square wave” can be defined as a non-sinusoidal periodic waveform that can be denoted as an infinite summary of sinusoidal waves. It has an alternate of amplitude at a fixed frequency between stable min and max value with the equal duration. Generally, this type of generator is used in various applications like electronics and in signal processing. This wave is the special example of rectangular wave. The square wave generator is just similar to a Schmitt trigger in which the reference voltage for the comparator depends on the o/p voltage. It is also called as an astable multivibrator.
Square Wave Generator using 741 Op-Amp
What is an 741 IC Op-Amp?
741 IC is a very common monolithic op-amp that can be used in a lot of applications. This op amp was first introduced by “Signetics” and now a lot of makers produce them. IC 741 is commonly available in an 8-pin DIP plastic package and includes a single op amp.
The typical applications of IC741 are Integrator, differentiator, adder, differential amplifier, subtractor, instrumentation amplifier, small signal audio amplifier, frequency generator etc. Even though this commonly operates from a split power supply, and it can be co-operated to work on a single supply. The pin structure of IC741 op-amp is shown in the figure below.
The range of voltage supply ranges from +/- 5V to +/- 18V. The two pins 1 & 5 are meant for adjustment of offset error. This process can be done by attaching a 10K pot with its end connected to pin 1, pin2 and the viper to pin-4. The maximum power of op-amp can dissipate is 500mW. Extra driver circuits are necessary for any application that needs more than the above stated power rating.
Square waves belong to an extensive range of frequencies and duty cycle can be produced using the 741 op-amp. The typical square wave oscillator using the uA741 circuit diagram is shown in the figure below.
In the above circuit diagram, the C1 capacitor and R1 potentiometer forms the timing part. Resistors R2 & R3 forms a voltage divider n/w which supplies a static fraction of the o/p voltage into the non-inverting pin of the op-amp as a reference voltage.
Square Wave Generator using 741 Op-Amp Working
Initially, the voltage across the ‘C1’capacitor will be zero and the o/p of the op-amp will be high. As a result, the ‘C1’capacitor starts charging to +Ve voltage through ‘R1’ potentiometer. When the ‘C1’capacitor is charged with a level so that the voltage at the inverting terminal of the op-amp is above the voltage at the non-inverting terminal. The output of the op-amp swings to negative.
The capacitor rapidly discharges through R1 and then starts charging to negative voltage. When the ‘C1’ is charged to a negative voltage so that the voltage at the inverting i/p more negative than that of the non-inverting pin. The o/p of the op-amp swings back to positive voltage. Now the capacitor rapidly discharges the negative voltage through ‘R1’ and starts charging to +Ve voltage. This cycle is recurrent infinite and the outcome will a nonstop square wave swinging between +Vcc &-Vcc at the output.
The time period of the o/p of the op-amp square wave generator can be expressed using the equation below.
T = 2 X 2.303 R1C1 log10 (2R3 + R2/R2) Sec
The common exercise is to make the R3 equivalent to R2. Then the equation for the time period can be simplified as
T = 2.1976R1C1
The frequency can be defined by the equation: F=1/T, and the frequency of the square-wave is independent of output voltage. The circuit is also named as astable multivibrator or free-running due to its quasi-stable states. The o/p remains in one state for T1 time and then makes a sudden transition to the other state and remains in that state for T2 time. The cycle recurrences itself after time T = (T1 + T2) where ‘T’ is the time period of the square-wave.
The square-wave generator using op-amp is beneficial in the frequency range of about 10 Hz to10 kHz. At upper frequencies, the slew rate of the op-amp limits the slope of the o/p square wave. The balance of the output waveform is dependent on the corresponding of two Zener diodes namely Z1 and Z2. The irregular square-wave (T1 not equal to T2) can be had by using various factors for charging the capacitor to +Vout & -Vout.
Thus, this is all about square wave generator using op-amp, what is an op-amp and it’s working. We hope that you have got a better understanding of this concept. Furthermore, any doubts regarding this concept or to implement electrical or electronic projects. Please give your valuable suggestions by commenting in the comment section below. Here is a question for you,what is the function of a square wave generator?