Here LM358 operational amplifier as an integrator is studied and analyzed using Multisim Circuit simulation software. The integrator circuit is studied in two forms- dual power supply and single power supply. An input square wave signal is applied to the op-amp integrator which is build with gain of 10. When the input is square wave to an integrator, the output signal is a triangle wave. It is easier to construct operational amplifier as an integrator with dual power supply but difficult with single power supply. But there is advantage in using single power supply and since one of the advantage of LM358 op-amp is that it can be operated with single power supply, the analysis here can be useful in construction of LM358 based single supply integrator circuit.
The theory of ideal op-amp integrator was explained with equation for gain, frequency response etc in the tutorial How to design Basic or Ideal Op-Amp Integrator Circuit. The theory of overcoming the limitation of ideal integrator was explained in the tutorial How to design practical Op-Amp Integrator Circuit. Here we analyze the op-amp integrator circuit by varying the input signal frequency and see the effect on the output signal. It is shown that the amplitude of the triangle output wave is decreased when the frequency of the input signal is increased and vice versa. It is also shown that proper biasing and coupling capacitor are needed if single supply is to be used for op-amp integrator circuit otherwise the output signal will be clipped.
Case 1: Dual power supply +5V and -5V.
Let input be square wave with amplitude(Vin) = 325mV, frequency(f)=1KHz
The input and output signal on the multisim oscilloscope is shown below.
If frequency is decreased the amplitude of the output triangle wave increases and if the frequency is increased the amplitude of the output triangle wave decreases.
When f = 500Hz,
When f = 5KHz, the amplitude of output signal decreases,
Case 2: Single Supply of +5V
The input and output signal on the multisim oscilloscope is shown below.
Here the output triangle signal gets clamped at the lower end.
Effect of frequency:
When the frequency is decreased to f = 500Hz, the amplitude of the output signal is increased and there is saturation at the lower end.
When the frequency is increased to f =7KHz, the amplitude of the output signal is decreased but there is no saturation at the lower end.
Case 3: Single supply of +5V with voltage divider biasing
The value of the resistors, gain, frequency response, coupling capacitor and bypass capacitor were calculated in the tutorial How to Design LM358 Op-Amp Practical Integrator.
In this case the input and output signal waveform is shown below.
Next see how to build this integrator on breadboard and test it with Matlab/Simulink in real time LM358 Op-Amp Integrator Test with Matlab Simulink Oscilloscope.
