Power amplifier electronic circuits-tube audio rf amplifiers

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

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.
June 9th, 2010

FM Remote Encoder/Decoder Circuit

Circuit Description

The circuit diagram of FM remote encoder/decoder has been published here. The main parts of this circuit are the ICs RF 600E and RF 600D. This circuit consists of two main parts such as transmitter (encoder) section and receiver (decoder) section. Among these, the transmitter stage uses IC1 (RF 600E) as its core part and the receiver stage uses IC2 (RF 600D) as its core part. These devices are designed to provide a high level of security and it can operate from DC supply between 2 to 6.6V DC.

In the encoder section, pins 1 to 4 forms the switch inputs of IC1. When each push button switch is pressed a corresponding code will be generated at the pin 6 which is the output pin. Transistor Q1 is used for buffering the encoded signals.  After buffering, this signal is given to the FM transmitter module. In the decoder section based on IC2 has four digital data output pins (pins 17, 18, 1 and 2) corresponding to the switches S1 to S4 of the transmitter section. The receiver module receives the transmitted code and feds it to the data input (pin 9). After the signal processing in IC2 the transmitted signal will be obtained.

Circuit diagram

FM REMOTE ENCODER CIRCUIT

FM Remote Encoder Circuit

FM Remote Encoder Circuit

FM REMOTE DECODER CIRCUIT

FM Remote Decoder Circuit

FM Remote Decoder Circuit

Notes

  • Assemble the circuit on a good quality PCB.
  • The ICs can be operated from anything between 2V to 6.6V. It is better to use batteries for powering this circuit.
  • Use miniature push button switches for S1 to S5.
  • Various electronic circuits like remote control systems, remote alarm systems, anti theft alarms etc can be implemented using the RF600E/RF600D pair.

May 13th, 2010

FM Radio Circuit Using TDA 7000 IC

Circuit Description

Figure shows the circuit diagram of Single chip FM Radio circuit. This circuit is based on the monolithic IC TDA 7000 which is the central part of this circuit. This IC TDA 7000 contains a Frequency-Locked-Loop system having an intermediate frequency of 70 KHz. This IC is very much suitable for FM portable radios with minimum peripheral components.

The job of intermediate frequency selection is done by the RC filter of the circuit. Some alignment is needed in the resonant circuit for the oscillator. This is for selecting the reception frequency. A special circuit called mute circuit employed here to avoid spurious reception. This circuit is also helpful to eliminate noise in the input signal. IC TDA 7000 can withstand up to 10 V supply voltage. But here 6V DC supply is used for powering the circuit. An 8 Ohm speaker or headphone can be used at the audio output of this circuit.

Circuit Diagram

FM Radio Circuit Using TDA 7000 IC

FM Radio Circuit Using TDA 7000 IC

Notes

  • Use a good quality PCB to assemble this circuit.
  • The circuit given here is designed as per the data sheet.
  • Special steps are taken for this circuit to meet the radiation requirements.
  • Use a 50mm long insulated copper wire for antenna.
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