Description. Here is a low noise preamplifier design for dynamic microphones. The circuit is based on the uA739 IC from Fairchild Semiconductors. uA739 is a dual audio operational amplifier with high gain and excellent stability. Out of the two opamps available in the IC, only one is used here. The audio signals from the microphone […]
Description. This is the circuit of a based audio preamplifier which has very low noise. One FET and one BJT are used in this circuit. The audio signal to be amplified is coupled to the base of FET Q1 using capacitor C1 and resistor R3.Base of transistor Q2 is coupled to the drain terminal of
Description. This jet engine sound generator circuit is based on the sound generator IC HT2844P from Holtek Semiconductors. This particular IC can make four sounds namely low speed sound of jet engine, high speed sound of jet engine, missile sound and machine gun sound. Each of these sounds can be activated by connecting the pins
Description. Here is a very simple three transistor audio amplifier circuit that can deliver 250mW to a 8Ohm speaker. Complementary transistors BC337 and BC227 (Q3 and Q2) are used as the output pair. Transistor Q1 (BC 547) acts as the preamplifier.POT R5 can be used as a volume control. Capacitor C1 decouples the DC from
Description. Here is the circuit diagram of a 10W audio amplifier using the popular TDA2003 IC from SGS Thomson. The IC can easily deliver 10W to a 4 Ohms load at 18V DC supply voltage. The IC can be also operated from 12V and that makes it applicable in car audio systems. The useful features
Description. Here is a very useful lamp flasher circuit using the famous adjustable voltage regulator IC LM317T. LM317 can source up to 1A of current and so up to 12W lamps can be used with this flasher. Such a circuit finds huge application in automobiles. The frequency of the flashing depends on the value of
Description. Many audio mixer circuits have been published here. But I think, this one is the simplest of them. This very simple audio mixer circuit uses only one transistor. The base emitter junction of the transistor is biased by the diodes D1 and D2.The signals to be mixed are directly coupled to the base of
Description. This powerful lamp flasher circuit is ideal for use in automobiles. The circuit is based on IC LM395 (also known as super transistor) which is a very powerful integrated monolithic power transistor with features such as thermal overload protection, current limiting etc. In fact this IC is almost indestructible.The IC can handle currents up
Description. Here is the circuit diagram of a simple two transistor alarm circuit that can be operated from a 9V PP3 battery. Here the two transistors are wired to form an oscillator whose frequency increases when switch S2 is pressed and decreases when S2 is released. In order to attain this the base of Q1
Description. The circuit given here produces an alarm similar to the police siren. When you press the push button switch S2 capacitor C1 will charge and this will make the transistor Q1 to ON slowly. When the switch S1 is released the C1 will discharge and the transistor Q1 will become OFF slowly. When the
Description. The circuit given below is of a simple audio amplifier that can deliver 12W to an 8 Ohm speaker. Op amp IC TL081 is used as the preamplifier here. Actually any opamp with matching power supply ratings can be used instead of TL081.Transistors Q1 and Q2 (TIP125 and TIP120) comprises the power amplifier stage.
Description. This is the circuit diagram of a simple three transistor audio amplifier that can deliver around 100mW power to a 25 Ohm speaker. The diodes D1 and D2 provides a constant bias voltage for the transistors Q1 and Q2.The transistor Q1 works as a preamplifier. Transistors Q2 and Q3 drives the speaker. The type
Description. This simple circuit produces a beeping sound that lasts for around 3 seconds whenever you make a whistle. The CMOS Hex inverter CD4049 is the heart of this circuit. Out of the six inverters in CD4049, U1a is wired as an audio amplifier which amplifies the signal picked up by the microphone M1.The U1b
Description. Here is the circuit diagram of a simple 24W mono amplifier using IC TDA1516.The TDA1516 is an integrated class B power amplifier in a 13 pin SIL package. The IC has many useful features such as short circuit protection, load dump protection, thermal protection, reverse polarity protection etc. Here the IC is wired in
Description. Given below, is a very simple circuit that can be used for charging car batteries. In this circuit there is facility for monitoring the charging current and voltage. The circuit is based on the IC MC78T12ABT from Freescale.The IC is nothing but a 7812 in TO-3 package with 3A capacity. The transformer T1 steps
Description. Here is a simple 3 input mic mixer circuit using the popular uA 741 ICs. Four 741s are used here.IC1, IC2, IC3 are used as preamplifiers. They produce a gain of around 40 decibel to the individual input signals. The IC4 is wired as a summing amplifier to add the signals from three preamplifiers.IC4
Description. Here is the circuit diagram of a simple two transistor tone controller circuit. This circuit is based on the famous Baxandal tone control design. The transistor Q1 is wired an emitter follower to provide sufficient current gain and input impedance. The second transistor is used to voltage amplify the signal in. The network of
Description. TDA4935 is bipolar stereo amplifier IC that can be wired as a 2X15W stereo amplifier or a 30W mono BTL amplifier. The IC also features built in circuitry for over load protection and over temperature shut down. Here the IC is wired in stereo mode in order to deliver 15W power on each speaker.
Description. This is the circuit diagram of a low cost stereo line driver is given here. The circuit consists of only two transistors and few passive components. Each BC 109C transistor is wired as an emitter follower for driving each channel. The voltage gain of the emitter follower is unity, but it has a high
Description. Here is the circuit schematic of a simple audio surveillance system in which the transmitter will pickup sound from one location and the receiver at other location will reproduce it. The receiver and transmitter are connected by only one set of wire. Here both power supply and transmitted signal share the same wire. The
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Description. This is a simple electronic alarm circuit that imitates the chirping of a canary. The circuit is nothing but a Hartley oscillator with few more passive components added. As the capacitor C1 charges through the resistor R1 and the transistor Q1 is driven to cut off. This makes the oscillations to stop. As the
Description. Here is the circuit diagram of a simple 3 band graphic equalizer circuit using a single IC and few components. The IC used here is LF 351 which is a wide bandwidth single JFET operational amplifier. The high input impedance of the IC makes this circuit compatible with most of the audio signal sources.
Description. This circuit is a simple approach for converting a loud speaker into a microphone. When the sound waves fall on the diaphragm of a speaker, there will be fluctuations in the coil and there will be a small proportional induced voltage. Usually this induced voltage is very low in magnitude and useless. Here in
Description. Here is a simple IR audio link that can be used to transmit audio signals up to 4 meters. The signal to be transmitted is applied to the base of Q1 via resistor R4.The transistor Q1 drives the IR transmitting diodes D1 and D2.The audio input will be modulated to the IR signals transmitted.
