Sunday, December 25, 2011

Make These Simple IC 741 Opamp Circuit Design Projects

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.

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:



Inverting DC Amplifier: 

Sometimes it becomes important for amplifying DC voltages, the diagram 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.


Non-inverting DC Amplifier: 


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.
 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.


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.

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.

40 comments:

  1. hi sir, do i need a dual power supply +12/0/-12 to drive these opamps im confuse?

    Regards,

    ReplyDelete
    Replies
    1. Hi Roger,

      Yes you will require a dual power supply for all these circuits.

      Delete
    2. It is also possible using two individual sources .

      Delete
    3. It has to be from one power supply.

      Delete
  2. 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

    ReplyDelete
    Replies
    1. A dual supply will be required for the above circuits, single supply will not work. You will have to use two 12v batteries.

      Delete
  3. 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.)

    ReplyDelete
    Replies
    1. Please tell me what is the power output of your portable amp, if it's too high then it won't be feasible...

      Delete
    2. 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.

      Delete
  4. 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!

    ReplyDelete
    Replies
    1. Hi Rhum,

      50 watt is too high, a cell phone battery will not be able to support such high power load.

      Delete
  5. 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

    ReplyDelete
    Replies
    1. 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.

      Delete
    2. 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.

      Delete
  6. 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!!!

    ReplyDelete
    Replies
    1. Good day, do you want a water flow sensor circuit or just a simple water sensor circuit??

      Delete
    2. Sir, good day, ahm, water flow sensor circuit sir. . . can i ask for the diagram?

      thanks.

      Delete
    3. Good day, presently I do not have this circuit, will try to figure it out.

      Delete
  7. Sir, Do you reside in bangalore? i just thought it would be good if we could meet once to talk on engineering and prototyping an electronic circuit.

    ReplyDelete
    Replies
    1. Thanks Ashwin! I stay in Mumbai, I wish we could meet.

      Delete
    2. Thanks Ashwin! I stay in Mumbai, I wish we could meet.

      Delete
  8. Hi Sir,
    i want to make a ic555 touch switch but cant't find enough info
    can you give me detail info and circuit diagrams?

    ReplyDelete
    Replies
    1. Hi Shiva,

      check out this one:

      http://talkingelectronics.com/FreeProjects/555/555-TouchSw.gif

      Delete
  9. hi.
    Swagatam..can i have your mobile number for query ???
    e-mail me kartikeyyadav@ymail.com

    ReplyDelete
    Replies
    1. I am sorry, i am comfortable interacting only through my blog.

      Delete
  10. I have 9 mv AC signal need to be amplified upto 5V.which circuit can i use.

    Neel

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

      http://homemadecircuitsandschematics.blogspot.in/2012/10/1-watt-led-driver-using-joule-thief.html

      Delete
  11. hi sir
    can you send me a circuit of pre amplifier which gives output of bass only

    ReplyDelete
    Replies
    1. Hi Joshua,

      you can try this circuit:

      http://homemadecircuitsandschematics.blogspot.in/2013/06/make-this-low-pass-filter-circuit-for.html

      Delete
  12. 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.

    ReplyDelete
    Replies
    1. 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

      Delete
  13. 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.

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

      http://homemadecircuitsandschematics.blogspot.in/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.

      Delete
  14. Thank you very much sir . Once I done I let u know the result .

    ReplyDelete
  15. 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

    ReplyDelete
    Replies
    1. 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

      Delete
  16. 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.

    ReplyDelete
    Replies
    1. 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:

      http://homemadecircuitsandschematics.blogspot.in/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.

      Delete
  17. 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

    ReplyDelete
    Replies
    1. 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

      Delete

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