Very simple voltmeter with ic741a

This circuit can be used to measure the voltage to 15 volts.Using the current from the battery 9 volt,At 23 mA only.
Input circuit has a diode, to protect the Return terminal. And input impedance of the circuit, were more than 1 M ohm.

Heart of the circuit is op – amp number 741.Which acts as a comparator,When the voltage across the pin emitter-bass of the transistor Q1 is a great value.Resistance between the collector and emitter are charged less.Therefore, the voltage at pin 2 of IC1.Therefore less valuable, and the output of IC1 to pay current LED1 light.When we adjust to the middle leg of VR1 to lower pressure. Until the pin 3 of IC1 is low pressure over the two legs a little.LED1 off, it will be.If we adjust VR1 compared to the pressure they can pretend to know the scale at the VR1.Voltmeter can not be used to measure the pressure of the alternating current (ACV) home

Micro ampere meter circuit using uA741

The micro ampere meter shown here is basically a DC millivolt meter.The circuit gives full scale deflection for 0.1V input.The current to be measured is passed through a known resistance R and the voltage drop across it is measured.Here the IC 1 uA 741 op-amp is wired as a non inverting amplifier

Versatile tone control using IC 741

This tone control circuit. A circuit design feedback tone control. This helps the smooth bass voice circuit and a rate increase – reduction of the signal at 18 dB. The power supply circuit is used from 12-24 volt and Shine Power consumption is 10 mA.
The audio input is entered through the C1 coupling to the input signal to the Q1 growth signal by R1 and R2 divide the voltage. To bias the pin B of Q1 and R3 are limited to flow properly. Q1 is the e-limit circuit fault Peter Low Power Amplifier stand out in E via C2 to the region to adjust the bass – treble. Including C3, C4, C5, C6, R5, R6, R7, R8. The VR1 is adjusted – reduce the growth of low-frequency (BASS) and VR2 is increasing – rate of growth of the frequency High (TREBLE). from the signal that is adapted to go to the leg 2 (inverting amplifier signal to a phase) of IC1 and will expand the output of Pin 6 through a signal output from C8. Which can be connected to amplifier sound at all

Schmitt trigger circuit using IC uA 741

A Schmitt trigger circuit shows two distinct signal input levels for turning the circuit ON and OFF.The difference between the Von and Voff voltages called hysteris Schmitt triggers are useful in conbverting slowly rising waveforms into fast rising ones and in relay like application.

The circuit shown here uses a 741 with positive feedback via R5,R6 and R7 for fast switching.Voltage dividers R8 and r9 set the DC input voltage to the non-inverting input terminal to half the supply voltage.The amount of positive feedback depends on the ratio of R6 and r7.the larger the ratio,the smaller will be the hysterisis shown by the circuit.Potentiometer r2 sets the DC voltage to the inverting input terminal and thus sets the threshold voltage at which the signal will trigger the circuit.The input signal can be applied to either of the two input terminals

Universal mono preamplifier using ic lm741

This circuit is a mono pre amp circuit, which can be used with a variety of inputs.Can be applied for extending the phone and the other with
When AF IN input signal to pin 3 of IC1, and The voltage input to pin 2 of IC1.The IC number LM741 used to amplifier circuit,Output at Pin 6.
And access to the AF OUT to be applied to various tasks.VR1 is adjusted by the strength of the output signal sent to the AF OUT

Op-amp siren sound using ic 741

This circuit is the sound generator super siren, for use be alarm signal get by live frequency generator circuit that use , op-amp circuit. The principle works to are while still no press switch S1 will still have no the loud sound comes out from a loudspeaker SP1. When do pressure switch S1 then liberate C3 do something charge full until while press switch S1 and discharge go out. When liberate switch S1 come in at R7. Which perform in something limit current come in at 3 Non inverting legs of IC1a. By IC1, D1, D2, C1, C2 and R5 build be sound generator signal circuit then export come to way pin 6 of IC1a come to reach at pin 3 (Noninverting) of IC1b. By have R1 and R2 build be Dectector circuit. For do fining level has signal then signal to come out the way pin 7 of IC1b which will have flowing through comes in at pin B of Q1 for do something bias give Q1 bias. When Q1 work then make SP1 make a noise loud come out and make a noise poor loud C3 discharge be finished SP1 then stop make a noise loud

Active high pass filter circuit using LM741

This is active high pass filter circuit for 327Hz frequency using LM741. It will use to build Harmonic at 3 of 130.81 frequency have the value at least. More than the frequency Fundamental 30 dB, for output be sawtooth wave form for use in sound of music way system Electronic design will use the circuit filters three rank frequency. By have 3 dB you slopes can use Op-amp IC number LM741 or number LF351it will meet the frequency well

Negative to positive voltage Supply with LM741

In sometimes when friends want to modify negative voltage source from the outside is positive voltage. We try to come to see this circuit use op-amp IC LM741, be usable easily and, It can change R1,R2 for fix the expansion ratio has of the circuit with. See the detail in the circuit adds

Thermal Fan Controller by IC 741 and Diode

The controller uses one or more ordinary silicon diodes as a sensor, and uses a cheap opamp as the amplifier. I designed this circuit to use 12V computer fans, as these are now very easy to get cheaply. These fans typically draw about 200mA when running, so a small power transistor will be fine as the switch. I used a BD140 (1A, 6.5W), but almost anything you have to hand will work just as well

Protects steal touch model by IC741

Contain divide this friends many you may face a problem economical. A steal the very. Today I then beg for to advise the circuit protects steal again model that interesting. It is model to touch , the system will work when , steal touch at the metal detects. When you see the circuit may like ,because use the equipment that seek easy be IC 741 very the circuit has tall many rapidity. When human body which there is electronic signal flows through all the time , make that signal changes to come to at input change R4 to pin 3 of IC LM741 make it works cause Q1 and oval RY1 work with. The lead goes to are usable , friends fine VR1 for fix the rapidity has of the circuit. The detail is other see in the circuit has please yes

Dry Cell Battery Charger using LM741 and IC4011

This is Dry Cell Battery Charger Circuit. That can use charger battery get that about 12 hour. When apply to power supply 9 volt the equipment that fix in the circuit use for size battery AA. If use the size C or D should devalue of Resistor RX down be 68ohm and should not lead battery come to serial while voltage in cell battery lower 1.6V. The Comparator Circuit with (IC741) control Gate output from Pulse Oscillator at use the integrated circuit CMOS 4011 change Transistor that do infront charger battery until voltage tall 1.6V Comparator Circuit more make LED Flasher warn know for protect Charger battery expire. The next time is if friends have Dry Cell Battery that use be finished already , don’t abandon , try apply new again yes

Audio Indicator by 741

Audio Indicator by 741

This circuit can be used to remotely monitor a loudspeaker, alarm, or audio source for presence of an audio waveform. It can also be directly connected across loudspeaker terminals used as a peak indicator.

If you need to monitor some audio signal at a location that is either soundproof are too far away to actually hear the signal then you can use a circuit similar to this one. A remote indication that the audio source is active is provided visually, here in the form of a LED. Referring to the above circuit, the 10k preset is a level control which should be adjusted so that when the source ( audio signal or alarm ) is producing the desired amount of noise, the LED lights. The input stage is an inverting x100 amplifier made with a 741 op-amp

Dual Opamp Buffered Supply by 1458

Dual Opamp Buffered Supply by 741

There will be instances where the currents from each supply will be unequal. Where this is the case, the resistor divider is not sufficient, and the +ve and -ve voltages will be unequal. By using a cheap opamp (such as a uA741), a DC imbalance between supplies of up to about 15mA will not cause a problem. However, we can do better with a dual opamp (which will cost the same or less anyway), and increase the capability for up to about 30mA of difference between the two supplies.

Fan Controller by 741

Fan Controller by 741

The amplifier gets quite hot while in use, so decided to use a fan to cool it. The fan, however, adds a lot of noise. To get the best of both worlds, I thought I’d turn the fan on only when required. The circuit shown uses two forward-biased diodes, one as a sensor diode (at JP2) and the other as a reference diode (D2). The small difference in forward voltage drop is amplified by IC1 and used to drive T1. T1 turns on a fan when the temperature on the reference diode exceeds that at D2. D1 prevents inductive kickback from killng T1. B1 and C2 provide a rectified, regulated supply from the transformer’s auxiliary 12V winding. This prevents noise from the fan motor getting coupled to the rest of the amp.
R1 is used to adjust the temperature cutoff point. This is done by first adjusting it to remain permanently off (turn it both ways, whichever way causes it to turn off, turn it all the way there). Now let the amp run for a while at a reasonably loud volume, so that the output devices heat up. Now place the reference diode on the heatsink of the output devices and back down R1 until the fan just turns on. Make sure that the fan is positioned such that after a while, it cools down the output devices enough to turn itself off.
This and the next circuit are built on the same board, and use the same auxiliary 12V supply, to avoid loading the 78L12 and to prevent fan noise from being coupled into the amp

Microphone Mixer by 741

Microphone Mixer by 741

This relatively simple mixer was designed for three dynamic microphones, but can be re-designed for more or less. Level and tone controls are available to tailor the sound to your needs.

R1, R2, R3 3 1K 1/4W Resistor
R4, R5, R6 3 10K Logarithmic Pot
R7 1 1Meg 1/4W Resistor
R8, R10 2 10K 1/4W Resistor
R9, R11 2 100K Linear Pot
C1, C2, C5, C6 4 0.1uF Ceramic Disc Capacitor
C3, C4 2 22nF Ceramic Disc Capacitor
U1, U2 2 741 Op Amp
J1, J2, J3 3 Input Jacks Of Your Choice
MISC 1 Board, Wire, Knobs, IC Sockets

Temperature Window switch by IC 741

Temperature Window switch by IC 741

This circuit, is basically a resistance � sensing window switch, except that the �resistor� takes the form of an NTC thermistor and the circuit thus responds to temperature. TH1 must have a resistance in the range 500ohm – 9Kohm. RV1 is used to set half � supply volts on the RV1 � TH1 junction at the �mean� temperature

Part List

R1=4.7Kohm TH1=NTC thermistor 500ohm…..9Kohm Q2=BC214L
R2=2.2Kohm D1-2=1N4148 RL1=12V Relay >120ohm
RV1-2-3=10Kohm pot. D3=1N4001

Electromagnetic Field Detector with IC UA741 or LF351

Electromagnetic Field Detector with IC UA741 or LF351

This circuit is sensitive to low frequency electromagnetic radiation and will detect for example hidden wiring or the field that encompasses a transformer. Pickup is by a radial type inductor, used as a probe which responds well to low frequency changing magnetic and electric fields. Ordinary headphones are used to for detection. The field that surrounds a transformer is heard as a 50 or 60Hz buzz. The circuit is below

I threaded a length of screened cable through an old pen tube and soldered the ends to a radial type can inductor. I used 1mH. The inductor fitted snugly into the pen tube. The opposite end of the cable connects to the input of the opamp. Any opamp should work here, possibly better results may be achieved with a low noise FET type such as the LF351. The 2M2 potentiometer acts as a gain control and the output is a pair of headphones. Stereo types can be used if they are wired as mono. I used an 8 ohm type, but the circuit should work equally well with higher impedance types. The probe (shown below) may be connected via screened cable and a 3.5mm stereo plug and socket

Temperature Monitor with IC LM741 or LM301

Temperature Monitor with IC LM741 or LM301

My Friend want circuit Temperature Monitor for control relay. I find on internet , See to This Web http://www.mitedu.freeserve.co.uk/Circuits good article circuit. The Temperature Monitor use IC LM741 or IC 301 for test Temperature control relay switch.
read more detail:

Using a thermistor in the position shown makes a heat activated sensor. A change in temperature will
alter the output of the opamp and energize the relay and light the LED. Swapping the position of the
thermistor and 47k resistor makes a cold or frost alarm

2-30V 5Amp Power Supply Regulator With LM317,741,2SA1186

Here is Circuit power supply linear regulator. Volt output 2-30V and Current 5Amp. use IC LM317 for Circuit power supply Regulator and Transistor 2SA1186 for Boost up Current from IC LM317 (1.5A) to 5A output.
Detail more read in circuit

2-30V 5Amp Power Supply Regulator With LM317,741,2SA1186

Relay Timer switch By IC 555 and 741

Relay Timer switch By IC 555 and 741

In Fig.1 see a 100 second delayed turn ON relay RL1 switch, if plug power +12V in circuit. In Fig.2 see a two range 6-60 second and 1-10 minute auto turn off relay timer circuit, with 555.

R1=1 Mohms C4=100nF 63V IC2=LM555
R2=330 Kohms C1-2=100uF 16V RV1=470 Kohms pot.
R3=680 ohms C3=1000uF 16V RL1-2=12V >120 ohms Relay
R4=2.2 Kohms D1=1N4148 S1-2=Push button n.o
R5-7=4.7 Kohms D2-3-4=1N4001 S3=2X2 switch
R6=47 Kohms Q1=BC214
R8-9=22 Kohms IC1=LM741

741+2N3055 linear power supply 13.8V 20A

741+2N3055 linear power supply 13.8V 20A

This be high current power supply circuit , Which there is the size voltage 13.8V at 20A.By it uses base equipment that seeks to buy easy, be integrated number circuit LM741 perform maintain one’s position voltage be stable or Regulated at 13.8V. Which can fine can decorate a little again. Besides still have the power transistors 2N3055 X4 numbers bring to build parallel perform enlarge current tall arrive at 20Amp Other detail , see in the circuit

Charger battery Lithium Variable current up to 2A by L200

Charger battery Lithium Variable current up to 2A by L200

This is circuit Charger battery Lithium Variable current up to 2A by IC L200. I’ve always wanted a fully adjustable current DIY lipo charger (and recently higher output).

The L200 datasheet has an LM741 op amp design to achieve this. It works well but has a very non-linear action (worse with a log pot). So with James Hopper’s help I have tweaked this design to produce near linear current adjustment with a standard linear pot. In my version, current is variable from about 100mA – 2A. The circuit is slightly more complex but is nicer to use. Here it is in EAGLE and image formats below.

R3 is a current sensing resistor which feeds the LM741 with a voltage that varies according to current flow. This gets amplified by the op amp which tells the L200 to change current. I have used a 100mm length of 0.5mm insulated copper wire for R3 (= ~0.010 ohms). The precise value is not critical. However, it interacts with the gain of the op amp and affects the minimum charge current and overall current range. Although I have tested with a value half this size (0.005 ohms), R3 should be larger rather than smaller than the 0.010 shown (eg: between 0.010 and 0.100 ohm). A larger R3 will give a smaller starting current.

The gain of the op amp is set by the ratio created by R2 (470ohm), R6 (10k pot) and R7 (250k trimmer). It also depends on the value of R3 above. If you want a lower start current it is best to increase the value of R3 as suggested above. However, reducing R2 (say to 220ohms) will have a similar effect.

L200‘s are internally limited to about 2A and this circuit makes an obvious correction if you go over this (you are likely to see current suddenly drop a bit as you rotate the pot over the 2A level). R7 is used to fine-tune the op amp’s gain and I recommend you adjust it so that max current can only get to just under 2A. If you can’t find a 250k trim pot then use a 100k trimmer with 150k resistor in series between R6 and R7 (eg: as shown in the first photo above). R7 does not require great precision so a single turn trimmer is fine.

The output voltage is set by the combination of R4 (1k) and R5 (5k trimmer). These values are suitable for 3 lipos (12.6v). A multi-turn trimmer is not essential but it does make it much easier to set the voltage accurately. A 10k trimmer is also OK.

The L200/LM741 design allows some leakage from cells connected while the circuit is not powered. This leakage is <20mA so is not very significant. Nevertheless, D1 prevents this loss, but more importantly protects the circuit from reverse polarity and any disasters that this may cause. It is therefore optional but I think strongly recommended. D1 would normally be a Schottky diode. It needs to be rated in excess of the circuit’s output current and voltage, and it is desirable to have a low a forward voltage drop and high reverse current capability. I’m using SMT versions which although small are not hard to use. Mine are rated at 3.5A, 30v, 0.35v and 535A. Not shown, but it would also be normal practice to protect the input from reverse polarity if it is being connected directly to a supply that can be reversed.

The L200 needs an input voltage that is at least 2v higher than the output to be able to yield the full rated output. You also need sufficient volts to cover the forward voltage drop of D1. With a 0.35V D1 drop, the input to the L200 needs to be 2.35V higher than the desired output (eg: 14.95v in for 12.6v out, perfect for a 15v supply…)

Auto-Fan, automatic temperature control by 741

Auto-Fan, automatic temperature control by 741

6 Input Mixer by IC 741 , LF351 ,TL071

A simple mixer with 3 line inputs and 3 mic inputs using commonly available parts.

The mixer circuit below has 3 line inputs and 3 mic inputs. The mic inputs are suitable for low impedance 200-1000R dynamic microphones. An ECM or condenser mic can also be used, but must have bias applied via a series resistor. As with any mixer circuit, a slight loss is always introduced. The final summing amplifier has a gain of 2 or 6dB to overcome this. The Input line level should be around 200mV RMS. The mic inputs are amplified about 100 times or by 40dB, the total gain with the mixer is 46dB. The mic input is designed for microphones with outputs of about 2mV RMS at 1 meter. Most microphones meet this standard.

6 Input Mixer by IC 741 , LF351 ,TL071

The choice of op-amp is not critical in this circuit. Bipolar, FET input or MOS type op-amps can therefore be used; i.e 741, LF351, TL061, TL071, CA3140 etc

Low Pass Active Filter by LM741

Low Pass Active Filter by LM741
When you want to filter low frequency gives can change only. I thinks the Low Pass Active Filter circuit help you. Because of it uses IC LM741,then usable easy follow circuit image. We can fix the frequency is cut off get, by equipment value R1=R2 = R , and C1=C2=C When fix give 50Hz frequencies low only that can change. Values Show be valuable about 0dB = 50Hz , -3dB = 250Hz , -50dB = 10kHz Then will see tall frequency 50Hz more cut give until less is finished. This circuit should use dual power supply positive,negative,GND +/- 5V to 18V in order to get a signal that is appropriate most

60Hz Notch Filter by LM741

60Hz Notch Filter by LM741

Level Detector by IC LM741

Level Detector by IC LM741
This circuit be the circuit checks voltage is easily. Or Level Detector by IC LM741 highly popular. By R1 keep fine the value voltage referable of the circuit. If Vin be valuable more than volt. The referable LED stick bright

Basic Differentiator by LM741

Basic Differentiator by LM741

Bridge Amplifier by LM741

Circuit Bridge Amplifier by LM741

LM741 – Op-AMP (Operational Amplifier)

General Description

The LM741 series are general purpose operational amplifiers which feature improved performance over industry standards like the LM709

Power supply regulator 0-30V 1A by IC 741 + Transistor 2N3055 & 2N3565

This is circuit power supply regulator variable voltage 0-30V at 1A.
it is old circuit I used IC ua741 or LM741 OP-AMP IC for control adjustable Votage by VR1 (see in image circuit).
The transister 2N3055 is classic part for booster current up to 1Amin.
I used transformer 2A. it big size in PCB but sure current peak 1A min.

Circuit power supply regulator 0-30V 1A by IC 741 + Transistor 2N3055+2N3565

PCB power supply regulator 0-30V 1A by IC 741 + Transistor 2N3055+2N3565

Dfferential Temperature Relay Switch by IC 741

Dfferential Temperature Relay Switch by IC 741
This is Circuit Dfferential Temperature Relay Switch .
Use IC 741 for control relay ad Diode D1,D2 for sencer Temperature . VR1 for adjusable voltage

Supply Splitter with IC 741& TIP41,TIP42

Circuit Supply Splitter with IC 741& TIP41,TIP42
If you must modify a place power supply. usual to dual power supply positive,negative,GND(0V). I introduces to try use. Circuit Supply Splitter with IC 741& TIP41,TIP42. When see the detail in the circuit make output of the circuit is pin GND(0V) the part is pin positive be +V part negative be -V there. When Transistor TIP41 and TIP42. Then make the circuit pays current get 100mA not exceed which enough be usable usual sir

Opto-Thermo Control Relay Switch with IC 741

Circuit Opto-Thermo Control Relay Switch with IC 741
This be Electronic switch circuit is onely. Which work with the light and the temperature. I begs for to call that Opto-Thermo Control Relay Switch with IC 741. By have work various instructions very much. And have onely observations be I uses IC 741 then can insist that. Must easy and economize. For electric appliances supervision as a result command change , Relay there. The detail is all see in a picture sir

Treble Booster By 741

You who like the treble may like this circuit. it is Treble Booster circuit help give the sound of music that you listens to bright go up. Besides it still build easy. The price is inexpensive with. Because of use IC 741 that excellent like again. instruction easiness press switch , as a result make the sound improves to follow want. And you can change the equipment has in the circuit with. See the detail can add sir.

circuit Treble Booster By 741

measurements temperature by diode 1N4148

measurements temperature by diode 1N4148

temperature by diode 1N4148 and ic 741.
easy to make and use.
Out to Voltmeter.
*** Low cost too !

When I wants the circuit takes the temperature to are simple. I uses Diode 1N4148 be formed check the temperature. By when feed voltage change it. It is have current flow be stable. When the temperature that Diode, change make Voltage. At it modifies with VR1 and VR2 fine decorate for show that is correct most fining decorates. The important I uses the temperature certainly compare with accurate temple. By compare with reserve 0 the degree Celsius per 0 Volt. For the certainty advises that, should use Digital Voltage Meter. Show well almost forget the important point should. Give power supply Regulator high-quality , such as IC 7815 and IC 7915 etc. Try usable this circuit sees, regard good base of the circuit takes the temperature sir