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IC 741 Opamp Design Projects

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The simple 741 opamp circuit design ideas presented here are not only interesting but also very amusing to build.
The included circuit ideas using IC 741 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:

IC 741 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.

 

IC 741 Non-inverting DC Amplifier circuit



Non-inverting DC Amplifier:

 

IC 741 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 741 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.

opamp741 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 IC 741

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 IC 741

 

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 IC 741

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...

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Forum Discussion - Ask a Question

  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

    Reply

    • 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.

      Reply

  5. 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 ….

    Reply

    • Hi Soundhirarasan, you can try a joule thief circuit as shown in this article:

      https://homemade-circuits.com/2012/10/1-watt-led-driver-using-joule-thief.html

      Reply

    • Ignatius, using a variable inductor might not be possible for me, but here's one that uses a different principle you can check it out:

      https://homemade-circuits.com/2014/06/making-ultrasonic-directive-speaker.html

      Reply

  7. 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

    Reply

  8. 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

    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

      Reply

  9. 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.

    Reply

    • Hi Akashdeep,

      opamp may not be required for such a simple enhancement, you can use two BJTs and configure them as shown in the following example article:

      https://homemade-circuits.com/2011/12/simple-and-useful-transistor-latch.html

      Eliminate R3 and the relay+diode, those are not required, now you can use the collector of T2 for triggering the MCU.

      Reply

  10. 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

    Reply

  12. 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.

    Reply

    • Prabhu, you can use LM358 IC for it.
      you can try the first design shown in the following article:

      https://homemade-circuits.com/2011/12/how-to-make-simple-low-battery-voltage.html

      replace the zener diode with 1K or 10K and adjust the 10k preset either to shut off or light up as you want in response to the selected resistor.

      Reply

    • You will need to make a small ferrite transformer for stepping it up. You can try the concept discussed in the following article:

      https://homemade-circuits.com/2012/10/1-watt-led-driver-using-joule-thief.html

      Reply

  19. Good day sir, i want to make a water flow sensor circuit using ua741 op amps but i cant search a circuit diagram. . can youhelp me for this sir. thanks and God Bless!!!

    Reply

  22. sir,
    i will forget that 50w portable audio amplifier, but can you help me to power up my lapel mic(rated 5 to 16w with 25w rms) since its power input ranges from 9v to 10v, if i can amplify a 3.7v battery form a cellphone it would be a big help on my part since i am using my lapel mic everyday in school. i have read a book talking electronics, there is a circuit there which was designed to boost 1.5v-4.5vdc upto 9v-10vdc, i already bought the components but the problem is there is no available rf choke inductor in my place and even the whole province. can you please help me… make my own voltage amplifier… really thank you for sharing your expertise to us… god bless you

    Reply

    • Hello Rhum,

      A cell phone batt is rated at 3.7V 0.8AH, it is to be discharged at not more than 100mA rate, so it's power output capacity is 3.7 x 0.1 = 0.37 watts max, how can we make it work with 5 to 16 watts load??

      By the way are you sure your mic consumes 5 to 16 watts?? just check it.

      Reply

    • Not sure what this mic is that takes so much power, but 25w rms is AC not DC. If it really does need 9v DC at 25W you will need a Motorbike or Alarm 12V sealed lead acid, and a simple voltage regulator to drop 12v to 9V. If your figures are correct you will need a Low dropout regulator with at least a 3A rating like the LM1085.
      If your figures are wrong and you need a lover wattage portable 9-10v supply, try 8 standard 1.2v rechargeables (AA or AAA) in series.
      If you still want to make the boost circuit, then inductors are quite easy to make for yourself.

      Reply

  23. sir,
    the power output of the voltage amplifier i'm trying to develop is 9v dc, since it is the required power input for my lapel mic(25w) and my 50w portable audio amplifier. it is very hard to find in our locality a 9v rechargeable battery and it is too expensive so im trying to develop a voltage amp so i may use my spare cellphone battery…tnx.. god bless!

    Reply

  24. sir,
    can you help me, i am thinking of a 3.7v battery from a cellphone to be amplified or boost to have an output voltage of 9v dc in which i can use as power source for my lapel mic and my portable audio amplifier. can you recommend a circuit for it SIR.. Pls… thank you in advance…(ps. i've already tried op amp LM741 with 1k and 1.4K resistors for non-inverting but still the voltage was'nt amplified… i tried also using transistors like bc547 & bc338 with resistors, diode, capacitor and ferrite coil assembly and did'nt work… pls help me sir.)

    Reply

    • For the 741 to output 9v it would have to have a power supply of at least 9v. To get a higher output than input you will have to convert to ac (oscillator) then use a transformer to change the voltage then rectify it. You will end up with a higher voltage but lower current.

      Reply

  25. do I have to use the dual power supply or could I connect it to ground???
    if I can't connect it to ground how could I use a standard twelve volt battery to acheive -12v?
    Thanks

    Reply

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