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Electronic Amplifier Circuits-Power amplifier, audio amplifier designs and circuits

April 28th, 2010

50 Watt Transistor Amplifier Circuit

Circuit Description

The circuit diagram given below is 50 W transistor amplifier. This circuit is a class-B amplifier. In this circuit, seven transistors are used. Out of these transistors, six transistors acts as preamplifiers and the rest one is for driving the speaker. The transistor 2N 3055 is used here to drive the speaker. The 500 ohm pot connected to BC 107 transistor is used for adjusting maximum power level of the amplifier.

In audio applications always use power amplifiers. This circuit is a very rugged and reasonably power amplifier. The capacitors C1 (220 uF) and C2 (100-200 uF) is for controlling low and high frequencies respectively. The circuit can be powered using a 50 V DC power supply with 5A current rating. Up to 60 V can be given to the circuit. This amplifier can produce 60W rms at 50V supply on an 8 Ohm load.

Circuit Diagram

50 Watt Transistor Amplifier Circuit

50 Watt Transistor Amplifier Circuit

Notes

  • The circuit is designed such that most of the components are not critical and can be easily replaced by nearest values
  • This circuit is ideal to assemble from your electronics junk box
  • Volume control can be added to the circuit¬†by connecting a 10 K POT in series to the input of the amplifier.
April 28th, 2010

Telephone Pickup Pre-amplifier using 741 IC

Circuit Description

The following circuit gives the circuit diagram of Telephone pickup Preamplifier. The central part of this circuit is the operational amplifier IC uA 741. This operational amplifier is used to pick up telephone signals. In this circuit, operational amplifier IC uA 741 acts as inverting amplifier. The gain of the amplifier is determined by the feedback resistor R4 (2M). This port resistor R4 can also be used for gain adjustments in this circuit. The gain to drive headphone Z1 is produced by the operational amplifier.

The tracking of telephone is done by high impendence magnetic core. If a high impedance magnetic core is placed near a telephone instrument or near one of the telephone wires, it picks up inductively both sides of the telephonic conversation without any electrical contact. The coil L1 used here can have 3000 turns of 0.4mm. The power supply for this circuit is 9 to 24 V DC supply.

Circuit Diagram

Telephone Pickup Pre-amplifier using 741 IC

Telephone Pickup Pre-amplifier using 741 IC

Notes

  • Use a good quality PCB or common board to assemble this particular circuit.
  • The circuit can be used as a telephone bug too.
  • Use 5000 turns for L1 if pick up with 3000 turns is not good.
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