Power amplifier electronic circuits-tube audio rf amplifiers

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

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.

June 9th, 2010

Switching Regulator Circuit

Circuit Description

The circuit diagram of 3A switching regulator has been published here. The central part of this circuit is the IC LM 317. This voltage regulator can deliver a maximum output current of 3A. The input voltage range of this circuit is between 8 and 35V DC. The output voltage of the circuit can be adjusted between 1.8 to 32V DC. The output voltage is adjusted by using the potentiometer R4 (5K). One of the main advantages of switching regulators over liner regulators is its power efficiency.

Switching regulator operates by taking energy from the input voltage source and then transferring it to the output with the help of a solid state switch and a control circuitry. There is no wastage of energy in switching voltage regulators since the switching element is either fully open or closed at any moment. The efficiency of switching voltage regulators is around 85%. The rate of energy transfer from input to output is controlled by the control circuit by controlling the duty cycle of the solid state switch.

Circuit Diagram

Switching Regulator Circuit

Switching Regulator Circuit

Notes

  • Use a good quality PCB to assemble this circuit.
  • The electronic circuit given here is a simple and low cost switching regulator.
  • Adequate heat sinks should be provided for IC1 and Q1.
  • Capacitor C1 must be a solid tantalum capacitor.

June 2nd, 2010

Microphone Pre-amplifier Circuit

Circuit Description

Here is the circuit diagram of three input microphone preamplifier. This is a mic mixer preamplifier centered on the high gain operational amplifier IC LM 348. This IC LM 348 is a quad operational amplifier IC that is it has four operational amplifiers embedded in this chip. This IC has also got some advanced features such as very high gain, class AB output stage and very low input supply current of 0.6 mA for each op-amp.

The 3 channels of mic input require three amplifiers. The three op-amps (IC1b, IC1c and IC1d) out of four in the IC LM 348 are used here as input amplifiers for the corresponding channels. This three input amplifiers are made in this circuit work as non-inverting amplifiers. The operational amplifier IC1a is the output amplifier in this circuit. IC1a is wired as inverting amplifier here. The output from each input amplifiers are given to the inverting terminal of output op-amp. IC1a mixes the signals from each channel and produces the required output.

Circuit diagram

Microphone Pre-amplifier Circuit

Microphone Pre-amplifier Circuit

Notes

  • Use a good quality PCB to assemble this circuit.
  • IC LM 348 operates from a dual power supply. A +12/-12V DC dual supply is used here for powering the circuit.
  • The gain of individual channels can be adjusted by using potentiometers R5, R6 and R7.