Power amplifier electronic circuits-tube audio rf amplifiers

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

June 10th, 2010

Voltage Doubler Circuit

Circuit Description

The circuit diagram given here is a simple voltage doubler circuit. In this circuit the central part is the timer IC NE 555. This circuit also includes two transistors Q1 (BC 107) and Q2 (BC 177) as its main part. The actual output current delivered by this circuit is 50 mA and it is suitable only for low current applications. The output voltage of this circuit will be approximately 19V for 12V DC input voltage.

In this circuit, the IC1 NE 555 acts as astable multivibrator operates at a frequency of 9 KHz. The output of this astable multivibrator is connected to the base of the transistors Q1 and Q2. The capacitor C3 is connected in such a way that its negative terminal is shorted to the output of two transistors. When the output of the astable multivibrator becomes low, Q1 will be off and Q2 will be on and capacitor charges. When the output of astable multivibrator goes high, reverse will happen and capacitor again charges to the double of the supply voltage. So the final output across capacitor C4 will be the double of the input voltage.

Circuit Diagram

Voltage Doubler Circuit

Voltage Doubler Circuit

Notes

  • Use a Vero board to assemble this circuit.
  • Use a holder to mount IC1.
June 10th, 2010

3-Phase Auto Changer Circuit

Circuit Description

The circuit given here is a three phase auto charger circuit. Any modern electrical or electronic device can operate from 230 V ac supply with 15% tolerance in voltage. That is the device will work normally for a voltage range between 195V and 265V. The device may not work properly beyond this range of voltage. To change over to the other phase, the voltage required for can be chosen. Here in this circuit, a step down transformer with a secondary voltage of 15-0-15 volt at 500 mA is used for the operation of 18V relay. Here switching of the relay can be controlled by the resistors R3 and R1 respectively.

Circuit diagram

3-Phase Auto-Changer Circuit

3-Phase Auto-Changer Circuit

Connection diagram

3-Phase Auto changer circuit-Connection Diagram

3-Phase Auto changer circuit-Connection Diagram

Notes

  • The circuit given here is designed by Mr.Seetharaman V.S from Chennai.
  • Transformer T1 can be a 15-015 V secondary, 230V primary, 500mA step down transformer.
  • For chatter free operation, use a capacitor of 100μF 40 volts in parallel with relay.
  • Use one mould for each phase.
  • The connection diagram given above gives the relay interconnections.
June 9th, 2010

Baxendall Circuit

Circuit Description

Here is the circuit diagram of Baxendall tune control circuit. The name Baxendall for this circuit is because this circuit is based on the tune control circuit developed by Baxendall. This circuit uses two transistors Q1 and Q2 (BC 109C) which are the central active components in this circuit. This circuit can produce a maximum cut or boost of around 12 dB at 10 KHz (treble) and 50Hz (bass).

The whole circuit consists of three stages such as input stage, Baxendall circuitry and output stage. The input stage is an emitter follower centered on transistor Q1 and consisting of resistors R1 (560K), R2 (470K) and R3 (2.2K). This input stage has unity gain and the output of this stage is fed to the Baxendall stage through the capacitor C1 (10 uF). Potentiometers R7 and R10 (47K) are used for the adjustment of bass and treble respectively. The output stage of this circuit consists of transistor Q2 and resistors R11 (2.7M), R12 (10K) and R13 (2.2K). The output of second stage is given to the output stage and the final audio output is produced from the output stage with a gain of three.

Circuit diagram

Baxendall Circuit

Baxendall Circuit

Notes

  • Assemble the circuit on a good quality PCB.
  • A 12V DC supply is used for powering this circuit.
  • Both the bass and treble can be independently adjusted.
  • The input stage of this circuit has an impedance of 225 kilo ohms.