AmplifierCircuits

This audio amplifier circuit is useful in classrooms to reduce the strain of lecturing ,if the surrounding environment is noisy. It uses the power amplifier IC LM380 that gives 2 watts output which is sufficient in a confined area. The amplifier is portable and the whole circuit and the battery can be enclosed in the Speaker box itself. The circuit uses a preamplifier stage around NPN transistor BC 548 and a power amplifier around LM380.An external Collar MIC can be given to the input using an audio jack .The voice signals are amplified by T1 and fed to IC1 input through the volume control VR. Capacitor C3 reduce the undesirable howling from the speaker. LM380  is the general purpose audio amplifier and its gain is internally fixed at  34 dB . Its output is short circuit proof with internal thermal limiting. The IC works between 5 to 22 volts DC and is dual in line version. Classroom Microphone System Circuit Schematic Audio Amplifier Classroom Microphone System C...

Classic Tone Control Circuit with Low Noise Transistor Tone control is a type of equalization used to make specific pitches or “frequencies” in an audio signal softer or louder. A tone control circuit is an electronic circuit that consists of a network of filters which modify the signal before it is fed to speakers, headphones or recording devices by way of an amplifier. Tone control allows listeners to adjust sound to their liking. It also enables them to compensate for recording deficiencies, hearing impairments, room acoustics or shortcomings with playback equipment. For example, older people with hearing problems may want to increase the loudness of high pitch sounds they have difficulty hearing. Tone control is also used to adjust an audio signal during recording. For instance, if the acoustics of the recording site cause it to absorb some frequencies more than others, tone control can be used to amplify or “boost” the frequencies the room dampens. This classic tone con...

This is a do it yourself wireless hardware keylogger project, consisting of a logging unit with a 2.4GHz transmitter, and a USB-based receiver. The project includes the schematics, PCB design, firmware, software and lots of additional files and data. A wireless keylogger is a perfect solution for monitoring user activity, at very low risk of disclosure, is a purely electronic device, so no access to the operating system is required. The Wireless Keylogger consists of two main building blocks: the transmitter, and the receiver. The actual keylogging takes place in the transmitter, which is in fact a PS/2 hardware keylogger, with a built-in 2.4 GHz wireless module. Captured keystroke data is transmitted through the radio-link in real-time, rather than getting stored. The receiver on the other hand, is a wireless acquisition unit with a USB interface. All keystroke data received from the transmitter is sent to the host computer via USB. From the software side, this data is available th...

LM567 Infrared Transmitter Circuit This infrared transmitter use PWM (pulse width modulation). The transmitter is equiped with LM567, tone decoder circuit. Audio signal ( at least 50mVvv ) is amplified with T1 and then it is used to modulate IC1. Infrared transmitter frequency is adjusted with P2 between 25 and 40KHz. LM567 Infrared Transmitter Circuit

Basic Low Power AM transmitter This transmitter is basic but allows transmission of audio to an AM radio. It consists of an RF oscillator operating in the AM broadcast band, together with a modulator stage, which mixes the incoming audio and the RF. A signal appears on the output, which has an AM component that can be picked up on a nearby AM radio receiver. Basic Low Power AM transmitter The transmitter consists of oscillator stage Q1 and modulator/buffer stage Q2. Q1 is biased via R1, R2, and R3. L1, C3, and C4 form the tank circuit with feedback network C3-C4 providing feedback to the emitter of Q1. RF voltage at the junction of C3 and L1 drives buffer/modulator stage Q2. Q2 is biased by base current produced by RF rectification in the base emitter junction of Q2. C6 is an RF and AF bypass capacitor. C9, C10, and L2 form the tank circuit for the collector of Q2. RF is taken from the junction of C9 and C10 and fed to a sho...

Tone control is a type of equalization used to make specific pitches or “frequencies” in an audio signal softer or louder. A tone control circuit is an electronic circuit that consists of a network of filters which modify the signal before it is fed to speakers, headphones or recording devices by way of an amplifier.Tone control allows listeners to adjust sound to their liking. It also enables them to compensate for recording deficiencies, hearing impairments, room acoustics or shortcomings with playback equipment. For example, older people with hearing problems may want to increase the loudness of high pitch sounds they have difficulty hearing. Classic Tone Control Circuit with Low Noise Transistor Tone control is also used to adjust an audio signal during recording. For instance, if the acoustics of the recording site cause it to absorb some frequencies more than others, tone control can be used to amplify or “boost” the frequencies the room dampens. This classic tone co...

TPA3122D2 Class D Audio Amplifier TPA3122D2 IC is used as a class D audio amplifier and can deliver up to 15W of power at 10% distortions. The real advantage of using a class D amp, especially TPA3122 is the fact that this IC doesn’t need a heatsink because it has a high efficiency. Another great thing about it is that you can buy a $20 built-it-yourself kit or even cheaper from ebay but you need to be careful not to buy a fake one. TPA3122D2 Class D Audio Amplifier I discovered this IC while searching for an audio amplifier circuit that I need for the 2 x 10W/4Ω speakers received from my brother-in-law. I think that TPA3122 can provide enough power for what I need even though it can output only 8W with 1% distortions on a 4Ω speaker (something that some of you might find too low). The main reason I would choose this instead of a class A or B IC is the fact it doesn’t need a heatsink, so the whole amplifier will be lighter in weight and cheaper.