Simple IR audio link

john April 7, 2010 101 Comments
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. The transmitted IR signals will be picked by the photo transistor Q2.The emitter voltage of the transistor Q2 will change according to the sound...
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100 Watt sub woofer amplifier.

john January 23, 2018 814 Comments
Description. This is the circuit diagram of a fully transistorized sub woofer amplifier that can produce an output of 100W.There are seven transistors including four in the output stage. The transistors Q1 and Q2 form the preamplifier stage. Transistors Q4 to Q7 form the output stage. Since no ICs are used the circuit is very robust and can be easily assembled on a general purpose PCB. If you are not familiar with the basics of electronics, CircuitsToday has provided...
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Audio clipping indicator circuit

admin April 7, 2010 No Comments
Description. This circuit can be used to identify whether there is a clipping in a particular wave form. Clipping is a phenomenon in which the amplitude of a particular waveform drops before it reaches the expected limit. This circuit glows an LED as an indication if the signal under test has clipping. The circuit is very useful in sorting out distortion problems in amplifiers.   The circuit is based on a window comparator based on the two opamps inside...
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Signal tracer circuit.

admin April 7, 2010 10 Comments
Description. A high gain amplifier circuit that can be operated from a battery pack of 6 or 9 volt battery pack is shown here.The IC1 uA 741 is wired as a high gain non-inverting amplifier and its output is amplified by a pair of complementary transistors (Q1 & Q2) to drive the speaker.The negative feedback from the common emitter junction of the two transistor stabilizes the gain of the circuit.The resulting audio output is sufficient to serve as a...
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Guitar pre-amplifier using uA 741.

admin April 7, 2010 5 Comments
Description. A preamplifier circuit suitable for high impedance type electric guitar pickups is given here.The circuit is based on a uA 741 op-amp (IC1).The IC1 is wired as a non-inverting amplifier.The POT R1 can be used as a volume controller.The POT R6 can be used as tone controller.The switch S1 is used to produce “brilliant” or “soft” tonal effects.   Circuit diagram with Parts list.   Notes.  Assemble the circuit on a good quality PCB or common board. The...
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Magnetic pickup pre-amplifier circuit.

admin April 7, 2010 3 Comments
Description. A preamplifier for magnetic pickups of record players is shown here.The uA 741 is used as an AC coupled non-inverting amplifier operating on a single supply.The amplifier gain is decided by the feedback components in which C2 controls the low frequency roll-off characteristics while C4 reduces the gain at high frequency end to compensate for the pickup characteristics.R3,R4 and R5 form a voltage divider to give a bias of about half the supply voltage to the non-inverting of...
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Crystal pickup pre-amplifier circuit

admin April 7, 2010 No Comments
Description. A preamplifier operating on a single supply and suitable for use with high impedance type crystal pickups is shown here.The circuit is basically a non-inverting AC amplifier in which the gain is dependent on the feedback resistor R4.The smaller is the R4,the lower will be the gain.The low frequency roll off characteristics are decided by C3. Voltage divider network comprising of R1,R2 and R5 provide a DC bias of about half the supply voltage R5 and C2 from...
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Power megaphone circuit

admin April 7, 2010 8 Comments
Description. Just about any power transistor can be used in  this megaphone.Its suitable for boats,playing fields etc.the transistors Q1  & Q2 are the HEP-230 type which are easily available in the market.The transistors are parallely connected to handle the required power and speaker matching.The microphone is a carbon type like that used in telephone hand sets.If  a regular carbon mike is used the push-to-talk (PTT) switch can be connected in place of S1 to provide PTT operation.There will be...
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FM adaptor circuit for car stereo

jacky April 7, 2010 7 Comments
Description. With this compact FM adaptor circuit plugged into the audio out of your cassete player or i Pod out put,you can listen your favorite music on your car stereo.This circuit is very useful if your car stereo doesnot have an auxillary in socket.The circuit is nothing buy  an short range  FM transimitter. The FM transmitter circuit is based on low power NPN transistor 2N2222.The tank circuit consisting of L1 & C1 producess the necessary oscillations at the collector...
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Head phone amplifier circuit

admin April 7, 2010 2 Comments
Description. Here is a simple head phone amplifier circuit that can be used to drive your head phone if your music player doesn’t have  enough power to drive your head phones.The circuit is straight forward and uses only three transistors. The transistor Q1 (BC 239) and associated components forms a pre amplifier.The transistor pairs Q2 & Q3 (BC 337 & BC 327) forms the driver circuit for the speaker. Power amplification is attained at this stage.The emitter voltage of...
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