741 op amp frequency response for speakers

Operational amplifiers op-amps are some of the most important, widely used, and versatile circuits in use today. The first op-amp used vacuum tubes and was released in by Bell Labs. The ubiquitous ua was released in and is considered by many to be the standard upon which others are based. It is still in production today from various manufacturers. Designed to amplify a small signal up to something useful, op-amps are applicable in an extremely wide range of projects, everything from audio circuits, to data acquisition, to signal processing. My goal is to simplify the op-amp into something easy and fun to use, highlighting the important stuff and keeping it simple.

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• 2.1 Subwoofer amplifier
• How to Design a High-Pass and Low Pass Filter Circuits Quickly
• Which IC makes the best amplifier?
• Audio amplifier circuit lm741
• Active High Pass Filter
• Top analog threads on EDAboard.com – November
• Getting Started With Operational Amplifiers (OP-AMP)
• I + Understanding Impedances. Why do we need to know this?
• Vcc - Keysight
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2.1 Subwoofer amplifier

Using your new knowledge of how sound works and with a basic understanding of circuitry and electronics, you can construct an active noise-cancelling circuit ANC! This circuit can also be attached to headphone jacks to attach it to your heaphones! The main idea behind noise-cancelling headphones involves the placement of a microphone on the exterior of the headphones, which picks up external noise.

These sounds are then inverted every sign is changed i. In theory, the signal and the inverted noise would cancel each other out interference and superposition.

More complex noise-cancelling systems might also include microphones on the inside of the headphones to measure the amount of cancellation that is actually occurring.

Some systems that are purely digital may also include adaptive filtering techniques which would greatly increase the precision and accuracy of the cancellation. Such systems are quite sophisticated and beyond the scope of this project concepts such as filtering are not discussed on these webpages , which is of a primarily analogue design.

The systems outlined on this page follow the basic principles previously discussed. This method uses operational amplifiers op-amps used as an amplifier, among other things , resistors used to control the flow of electricity , and capacitors used to store electrical energy.

Note that these are the bare minimum of requirements. Small changes in resistor size or capacitance may be needed if you find certain things are not working. Also, these are the requirements for one channel if you are going for stereo , i. Double the requirements and build two circuits and you'll have a stereo system. The circuit diagram we need. It looks complicated but it can be broken down into large junks, don't be intimidated! The red lines divide the circuit into three sections corresponding to the sections in the block diagram below.

Click on the image for the source. There are three main parts to this circuit: a pre-amplifier , a delay or all-pass filter, and a summing amplifier. If you owned a pair of noise-cancelling headphones, you might have or might not have noticed that there is likely a tiny hole on the external casing of each ear-piece. These are actually microphones. These are the microphones that are the input at the far left of the diagram above.

What happens is that the noise an engine hum, for example is picked up by the external microphones. This wave goes into the pre-amplifier, which amplifies the input wave by increasing the amplitude. This is one of the most basic uses of an op-amp.

Think of it like a multiplicative factor and this factor is determined by the ratio of the two resistors. But why? Electrical signals travel at the speed of light. The time between the pre-amplifier and the summing amplifier is not negligible because of this difference in speed. When the noise travels from the environment to your ear, it travels with the speed of sound. However, when the noise travels from the environment, then through the microphone and the rest of the circuit and then out the circuit to your ear, there is some time during which it travels at the speed of light, as illustrated in the picture below.

So the delay works to line up the two signals. Lastly, the summing amplifier does two things: it combines multiple signals using the principle of superposition and it also is another amplifier. This stage combines the music with the processed noise signal and then inverts the resultant wave. This next stage amplifies the noise signal to a higher level that can actually be processed the waves themselves are tiny and would result in minute voltages which would be very difficult to deal with and is a simple op-amp circuit that provides a gain to the incoming signal see above.

The gain of this op-amp circuit is simply the ratio of the resistances and the increase is approximately and an added bonus from this circuit is that it will also help to reduce any DC components and offsets that may appear, because DC offsets in the noise cancelling signal will cause issues that will compound as the signals travel through the circuit and will result in a poorly working system.

From here the noise will pass to the delay. As mentioned earlier, the noise that is to be cancelled needs to be picked up by the external microphone and inverted and summed with other signals and this process takes time which is not instantaneous or negligible.

The all-pass filter provides the delay to the noise-cancelling signal that helps align all the signals and noise so that the summing process is much more effective. Recall that the noise from the environment is travelling at the speed of sound, which is much slower than the speed with which electric signals pass through the circuit. As a result of this, the noise from the environment actually will arrive an instant later than the inverted noise from the circuit to the ear and this will result in a weaker ANC.

Below is the schematic for the delay. The problem of the delay adds some more items to consider when constructing the all-pass filter. In fact, the specific headphones that are used will have an impact on this portion of the circuit, should you choose to use headphones. If you do decide to use headphones, this next bit is important. Consider a pair of headphones where the distance from the external microphone to the ear itself is L. If the speed of sound is V S and the time delay is t , then the time delay can be calculated through some algebra based on the equation for the speed of sound as.

This frequency needs to be decided and is based on the range that the ANC is expected to perform. R4, C3, and C4 can be manipulated to work this out. The oscilloscope or the speaker may be very useful when working on this part. This last op-amp set-up combines the amplified noise with the music to form a superposition of the two. Then this sum of the waveforms is inverted. The most difficult portion here is that the amplitudes of all the signals and noise match properly.

A potentiometer is used to aid this process. The gain of this primary component can be calculated as before. The input of the music will have no gain applied to it and the noise will have a gain of 0. This may seem a bit confusing here because the latter is clearly not an amplification but the exact opposite.

However, it will be called a gain for consistency. Perhaps the easiest way to make the amplitudes match is to manually test by adjusting the potentiometer until it sounds as if noise cancellation is taking place. Use the oscilloscope as well. Remember that all the resistances and capacitances provided are ballpark values and should be used as a guide. Make sure you are constantly checking with the oscilloscope and feel free to change some values as you see fit. Although this is an optional step, it would be good to complete for a few reasons.

The power supply filter, shown in the image above, is before the noise is passed to the first op-amp. In the schematic, C5-C7 and R11 act as a low-pass filter i. This is important because high frequency noise may be present and it would be a benefit to have it removed from the microphone output otherwise something known as aliasing might occur, which happens when the circuitry has problems identifying the frequency of a signal.

Aliasing causes distortions in the sound. Additionally, the resistor at R10 provides a bias essentially a DC offset if an electret microphone is used. The capacitor at C2 is used to remove the DC offset afterwards and only allow the noise that the microphone detects to pass.

The output from the capacitor then leads to the first primary component: the pre-amplifier. If you choose not to add headphones, you can still observe and hear the noise-cancelling effects with a speaker. This is a simple addition, instead of adding the headphones to the circuit see below , simply send the output of the summing amplifier to a speaker.

You may also consider adding a second summing amplifier to imitate what is going on in the ear. This second summing amplifier should take the first summed wave noise and music and combine it with the uninverted noise to imitate the cancellling. Then if the speaker is placed here, one can hear the effects. Experiment with placing the speaker at various parts of the circuit. For example, use it to hear the amplification of the pre-amplifier, use it to listen to the noise from the microphone, or use it to hear the effects of superposition in the summing amplifier.

The speaker is a nice tool for these observations. This final stage depends on the headphones that are being used. Headphones have an inherent impedance , essentially a resistance, associated with them check the specifications of your pair.

Ohm's Law describes the relationship between resistance, voltage, and current. However, this only works in the case of direct current DC. The alternating current AC analogue is. It is likely that this will be a much greater current than is safe for the headphones.

The resistance at R12 can be added and modified to limit this current to a value that is safe for the headphones. A lower current will also protect the ears as essentially the more current, the higher the volume. Now that the circuit is complete, the last thing to do is to attach the external microphones to the exterior of the heaphones and perform more tests you should be testing all along the way to make sure thing are working as they should, make sure you understand and see what is happening at each major section.

Your circuit should be up and running now! Previous Next. What is Sound? How do we hear sound? Waves Interference Resonance. Capacitors 0.

How to Design a High-Pass and Low Pass Filter Circuits Quickly

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Which IC makes the best amplifier?

Please log in to show your saved searches. Discover our broad range of op-amps for industrial, automotive and consumer applications. STMicroelectronics - UA Speed up your design by downloading all the EDA symbols, footprints and 3D models for your application. You have access to a large number of CAD formats to fit with your design toolchain. Please contact our sales support for information on specific devices. Distributor reported inventory date: This browser is out of date and not supported by st.

Audio amplifier circuit lm741

Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. I am seeing a signal on scope but I cant hear anything when I connect the speaker [I am measuring without it]. Moreover the scope image is the same as the input image ,no gain!

Active High Pass Filter

Using your new knowledge of how sound works and with a basic understanding of circuitry and electronics, you can construct an active noise-cancelling circuit ANC! This circuit can also be attached to headphone jacks to attach it to your heaphones! The main idea behind noise-cancelling headphones involves the placement of a microphone on the exterior of the headphones, which picks up external noise. These sounds are then inverted every sign is changed i. In theory, the signal and the inverted noise would cancel each other out interference and superposition. More complex noise-cancelling systems might also include microphones on the inside of the headphones to measure the amount of cancellation that is actually occurring.

Top analog threads on EDAboard.com – November

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Getting Started With Operational Amplifiers (OP-AMP)

In the previous tutorial, we have seen about Passive Filter i. As the name suggests, a High Pass Filter allows only high frequency components of a signal while restricting low frequency components. A high pass filter will allow the frequencies which are higher than the cut-off frequency and attenuate the frequencies lower than the cut off frequency. The amount of attenuation or the pass band range will depend on the designing parameters of the filter.

I + Understanding Impedances. Why do we need to know this?

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Vcc - Keysight

Operational amplifiers are the basic building blocks of Analogue electronic circuits. They are linear devices with all properties of a DC amplifier. We can use external resistors or capacitors to the Op Amp is many different ways to make them different forms of amplifies such as Inverting amplifier, Non inverting amplifier, Voltage follower, Comparator, Differential amplifier, Summing amplifier, Integrator etc. OPAMPs may be single, dual, quad etc. The ideal Op Amp has three important terminals in addition to other terminals.

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In this post we learn how to design audio filter circuits such as high pass filter and low pass filter circuits effortlessly without going through the hassles of complex simulation and calculations. The presented designs will enable creating filter circuits only for the desired specific frequency bands and block all other unwanted frequencies. As the name suggests a high-pass filter circuit is designed to attenuate all frequencies below a particular selected frequency, and pass or allow all frequencies above this threshold. The principle is just opposite to a low-pass filter circuit.