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Basic Op Amp Circuits Explained

Basic Op Amp Circuits Explained

The 8 fundamental 741 based opamp circuits presented here are not only interesting but also very amusing to build. The included circuit ideas like inverting and non-inverting amplifiers, tone control and regulated power supply will surely intrigue you. Circuit diagrams are also attached with the article.

 Overview

We all are probably aware regarding the high versatility of the IC 741. Amazingly an infinite number of 741 opamp circuit design ideas can be wired by adding just a few passive components to it. We investigate a few of them here. IC 741 is one of the most versatile and multipurpose op-amp and can be wired up in numerous different ways. Let’s study some of the important 741 opamp circuit design configurations:

Op amp Inverting DC Amplifier circuit

Inverting DC Amplifier:

Sometimes it becomes important for amplifying DC voltages, the diagram above shows how the IC can be wired up into an inverting DC amplifier circuit. As the name informs a DC input to the IC will be amplified at its output but will be just the opposite with polarity. VR1 may be used for adjusting the gain of the amplifier.

opamp Non-inverting DC Amplifier circuit

Non-inverting DC Amplifier:

Op amp Inverting AC Amplifier circuit

This configuration is similar to the above circuit, the only difference being the output response, which is always equal to the polarity of the fed input voltage.

Inverting AC Amplifier:

The figure shows how the basic inverting DC mode of the IC can be simply modified into an inverting AC amplifier design. This circuit is intended to be used with AC or oscillating input signals, primarily for amplifying minute frequencies. C1 and C2 form the input and the output coupling capacitors. Again here the gain may be varied using the pot VR1.

opamp Non-Inverting AC Amplifier circuit

 Non-Inverting AC Amplifier:

The circuit is similar to the above explained design; the only difference being the output of the circuit provides oscillations in phase with the input whereas the previous design produces oscillations with opposite phase to that of the input.

opamp Active Tone Control circuit

Active Tone Control:

The opamp IC741 can be very effectively used for processing audio frequencies and customizing them as per one’s own choice.

Folks who prefer more bass in music may achieve it by just adjusting the bass control shaft whereas those who appreciate extra treble with music may do the same through another similar control reserved for the purpose.

The circuit diagram shows how by adding just a few passive components with the IC 741 a neat little active tone control circuit can be built.



For the given values, the circuit provides a bass boost of 12.5 dB and a cut of 10.5 dB at around 100 Hz.

The treble chill is of 8.8 dB with a cut of 9.8 dB at around 10 kHz, with respect to the set gain of the device at 1 kHz. The circuit also features high input impedance and low output impedance.

Regulated Power Supply Circuit Using opamp

Regulated Power Supply Circuit Using opamp IC 741

The final diagram of this article shows a classic regulated voltage DC power supply using 741 opamp circuit design.

A cheap zener / resistor voltage reference is used to provide a reasonably stable reference to the non-inverting input of the IC.

The pot VR 1 is used to set the output voltage right from zero to a maximum of 15 volts continuously. A Darlington pair transistor is used at the output to enhance high current delivering capacity.

However another transistor T3 has also been incorporated to check the above current if it tends to drift beyond limit.
The control limit may be set by varying the value of the resistor R6.

In this post we discuss a couple of interesting application circuits using IC 741 which includes a simple power amplifier circuit and a regulated power supply circuit

This blog includes many interesting circuits which incorporates the IC 741 as the main active component for implementing the proposed functions. The present post explains yet a couple of more useful IC 741 application circuit ideas especially designed for the new electronic hobbyists.

Power Amplifier Circuit using IC 741

The first circuit diagram shows how the IC 741 can be configured as a high power amplifier circuit.

Though the maximum power of this amplifier is not more than 4 watts, the amplifier provides relatively good response with the applied frequency. The distortion of less than 0.5% and has a bandwidth of over 20kHz. The amplifier requires a minimum input of around 150 mV.

Power Amplifier Circuit using an opamp

Regulated Power Supply Circuit using IC 741

The next circuit shows the IC 741 being wired up for providing a regulated power supply with an output which can be varied as per ones own requirement.Basically the IC is configured as a comparator cum driver for the proposed power delivering purpose. The employed zener diode has been included for fixing the non inverting of the IC with a constant refernce voltage.

An additional transistor BC107 has been included for making the circuit short circuit proof and also overload protected.

The output volts can be varied by adjusting the 10 K pot while the maximum current can be set by selecting or varying the 0.6 Ohm resistor appropriately as per the needs.

Regulated Power Supply Circuit using opamp

Well, these are the few popular IC 741 based opamp circuit ideas that I could collect and present, if you have more ideas regarding the topic please feel free to share them through the comments...

SHARING IS CARING!

About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!






30 thoughts on “Basic Op Amp Circuits Explained”

  1. Hi Swagatam, could you suggest a circuit for testing a 741 to see if it is okay the reason being that I have a few of them in my collection and wanting to know if they are okay to use. I am also wanting to build a non contact AC voltage detector that uses a 5v piezo buzzer and a led for audio and visual detection.

    Regards
    Geoff

    • Hi Geoff, you can connect the opamp as a comparator and check the output response.

      connect any one of the input pins between the junction of two 10k resistors whose ends are connected to the supply rails.

      connect the other input terminal to the center lead of a 10k preset or pot whose outer terminals are also connected with the supply rails….

      connect a couple of LEDs, one from (+) to opamp output, and another from opamp output to (-), both having there own 1K resistors.

      now flipping the pot to and fro should light-up/shut-off the Led alternately…proving the correct working of the opamp.

  2. Is the power supply's output regulated?…
    How do I calculate the current limiter R6?…
    It's variable voltage but not current?…

    tnx for the patience 😀 Engr. Swagatam…

    • thanks Eshkariel 🙂

      yes the output will be regulated as long as the 24V or whatever input is fed is constant.

      R6 = 0.6/current limit value

  3. Hi sir, how to increase .5Vtoo 5v.? In my project i use piccontroller and sensor. My sensor gives oly .5v oly. So controller couldn 't take this voltage. How to boost up this voltage that can detect controller ..? Soundhirarasans@gmail.com… thanks in advance ….

  4. sir, i want to build a parametric oscillator circuit. using a variable inductor. please can you provide me a circuit diagram

  5. sir, I want to make an portable charger for a mobile by using a solar cell ,wind energy ,a battery and IC 741 so can you provide us circuit diagram and the list of component related to it as early as possible

  6. Hi swagatm,
    AS I mentioned that the Volts from the pulse coil at low rpms would be 200-250mv, may be 150 mv as well. So I have to eleminate R3 and the relay+diode and connect the collector pin of bc557(PNP) to the base of the PIC which will deliver 5 volts pulse to the PIC. Correct me If I am wrong.
    Now the next querry is at highr rpms when the voltage from the pulse coil is 8-10 volts, Do I have to add a zener between the pulse coil and R1.
    Waiting for your reply

    • Hi Akashdeep, yes that's correct……. by "base of PIC" did you mean the input of PIC?

      If the supply to the referred transistor circuit is fed with 5V then the input variations will not matter… . The collector of BC557 will always generate 5V regardless of the input variations.

      for a safer response make R1 = 100K

  7. Hi Swagatam,
    From the pulse coil of my bike I get a pulse of 250 mv at low rpm which is not sufficient for the micro-controller to sense. But at higher rpms The pulse goes up to 8-1- volt.
    I thought of adding an op-amp in between the Pulse coil and the micro-controller. So the pulse coil, a resistor, then 4007 diode, then a zener then op-amp and then to micro-controller. Will you plz specify how it should be with the schematics and the component values plz. The power source would be a 12 volt battery.

  8. sir its me again
    i have a low pass filter using [jrc4558] its is for home made [ home theater sub woofer] , its working but the problem is that i can here little transformer dramming coming from the sub woofer] its sounds mmgmmgmgmgmm….
    my question is how can i reduce this problem because its really bad especially working with power amplifier and opm

    • joshua, you can make and install a 50Hz notch filter circuit for sinking the interference or use an smps based circuit for powering the amp

  9. Sir, Tks for ur valuable comments . I understood. Ic 741 is for 1 o/p only . for my circuit I need to measure two resistors only . 1.2k & 4.5k only. Is there any dual op amp ic ? Pls help me n post the circuit sir .tks in advance.

  10. Hi sir , by using op amp can I measure resistance . I need a o/p in a led indication. Fixed value ..let say if 1k red led need to light up if 10k green led need to light up …..pls help ..tks.

    • Hi Prabhu, yes it can be done. But only for a single resistor for a particular setting, you cannot get multiple indications from one opamp at a time

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