Op Amp as an integrator

Op-amp as an integrator:

In the last article we have seen the op-amp comparator. Now we are going to learn another application of operational amplifier as integrator.

Integrator is a circuit whose output is proportional with the area of the input waveform. Following figure shows the op-amp as integrator circuit. We know that the RC circuit itself acts as a simple integrator. But in such circuits the output waveform is not exactly linear triangular waveform as it should be. In op-amp integrating circuit the inverting terminal is virtual grounded by the differential op-amp input circuit as shown in figure. Input current is equal to Vin/R1. As the input impedance of the op-amp is infinite all of I1 will flow to the capacitor.

op amp as an integrator
op amp as an integrator

Working of op-amp integrator:

Let us consider R1 is kept constant. Assume that the input voltage (Vin) is kept constant for a given period of time, hence the value of the I1 is also constant. Because of high impedance all of I1 flows through capacitor so that capacitor starts charging by a constant current source. When input voltage (Vin) is kept constant, the capacitor will charge and discharge at linear rate. The output of this op-amp integrator is shown below.

op amp integrator output waveforms
op amp integrator output waveforms

From the above output waveforms we can observed that when input voltage goes positive (from –V to +V) the output is a negative ramp. Similarly when the input goes negative (from +V to -V) the output is a positive ramp. This implies that the op-amp integrator output is 180 degree out of phase with the input.

We will see another application of operational amplifier i.e. op-amp audio amplifier in the next article.

Pin configuration of Op Amp:

op amp pin diagram
op amp pin diagram

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Audio Amplifier using Op-Amp: Electronics Project

This article provides an information about how to make an audio amplifier using an opamp. We will also try to explain the working of this audio amplifier using an opamp.

How to make audio amplifier using opamp

We have already studied some important applications of the operational amplifier such as op-amp comparator, op-amp integrator in the previous articles. Today we are going to learn another important application of op-amp as an audio amplifier and its working.

We know that the output of most of the communication receivers is the audio amplifier. Important characteristics of the ideal audio amplifier are listed below.

  1. High gain.
  2. Distortion should be minimum in the audio frequency range. (20Hz to 20KHz)
  3. Input resistance or impedance should be very high.
  4. Low output resistance to provide optimum coupling to the speaker.

If we use the operational amplifier in the audio amplifier, then it will cover all the characteristics listed above so as to make an ideal audio amplifier.

Circuit diagram

The following figure shows the circuit diagram of the audio amplifier using operation amplifier.

Audio amplifier using operation amplifier
Audio amplifier using operation amplifier

Working of audio amplifier

It should be noted that the op-amp is supplied only from +V volt power supply (usually 5V power supply), the –V terminal is grounded. This arrangement is made so as to get the output in the range (+V-1) volt and +1 volt. In audio amplifier coupling capacitor (Cc2) is used between the op-amp and speaker. The coupling capacitor is necessary to reference the speaker signal around the ground. The capacitor Cs is included in the Vcc line to prevent any transient current caused by the operation of op-amp from being coupled back to Q1 through the power supply.

Op amp (IC 741) pin configuration

op amp pin diagram
op amp pin diagram

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