Power amplifier electronic circuits-tube audio rf amplifiers

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

May 7th, 2010

Long Range FM Transmitter Circuit

Circuit Description

The circuit diagram of Long Range FM transmitter having a power output in the range of 0.5 -2W has been explained here. High power transmitters are required if the transmission path contains many obstacles or the transmission distance is very high. A micro transmitter can produce a power of a few thousandths of a watt. The battery using here should be of the alkaline high power type, because the current drain will be high when compared to micro transmitter current drain. The power output of the device can be altered by changing the value of the resistor R6. This can be done by putting a variable resistor of 1K in series with R6 so that it can be adjusted to get a variable output power.

The audio input to the power oscillator is formed by TR2 and associated components, is derived from a piezoelectric microphone. This is used to drive the simple audio frequency amplifier TR1. Potentiometer R1 is used to control the input of the audio amplifier which is done by selecting the correct amount of voltage that is generated by the piezoelectric microphone. Then this signal is connected to the base of TR1 by means of capacitor C7. RF feed back problem due to large RF field is solved by employing a metal enclosure for transmitter and keeping internal wirings short.

Component listing for 1 watt transmitter

Resistors: R1 (27K), R2 (330K), R3 (56K), R4, R5 (10K), R6 (100 ohm).

Semiconductors and other Devices: TR1 (BC547), TR2 (2N2219) fitted, MIC (piezoelectric microphone), L (6 turns 22 gauge enameled wire wound on 3⁄16″ former)

Capacitors: C1, C2, C3, C8 (330 pF), C4 (2–10 pF trimmer), C5 (47 pF), C6 (1 nF), C7, C8 (40uF).

Circuit diagram

Long Range FM Transmitter Circuit
Long Range FM Transmitter Circuit

Notes

  • DC power supply ranging from 6V to 30V can be used in this circuit
  • The variable resistor must not be a wire wound device since this would act as an inductor which will cause feedback problems.
  • It is possible to use an electret microphone instead of piezoelectric microphone.
April 25th, 2010

40 Watts Audio Amplifier Using IC TDA 2030

Circuit Description

The circuit diagram given below represents 40W audio amplifier. This 40W power amplifier circuit is designed using IC TDA 2030 and two transistors as main components. The IC TDA 2030 is the core part of this circuit because it plays the main role in voltage amplification. The job of current amplification is done by the two transistors. Adequate heat sinks should be provided for IC and both transistors.

The input signal is fed to the non- inverting terminal (pin 1) of TDA 2030 IC through the decoupling capacitor C5 (470 nF). When voltage amplification is performed by TDA 2030, the power supply current to IC changes with respect to the variation in the input signal. The variations in positive and negative supply pins of the IC are coupled to transistors Q1 (BD 712) and Q2 (BD 711). These transistors are connected complementary to each other in circuit so that they perform current amplification.

Power supply for the circuit can be 12V to 40V. Use 40V supply and 4 Ohms speaker for maximum output. To optimize the circuit performance, input and output grounds must be properly decoupled.

Circuit Diagram

40 Watts Audio Amplifier Using TDA 2030

40 Watts Audio Amplifier Using TDA 2030

Notes

  • Use a good quality PCB to assemble components for this circuit.
  • Make PCB tracks broader through which high current flows.

April 21st, 2010

4×15 Watt Power Amplifier Circuit

Circuit Description

4×15 watt power amplifier consists of four channels of amplifiers. The core part of the circuit is 15W BTL X 2 channel audio power amplifier IC TA 8215 developed by Toshiba. In this power amplifier circuit, two TA 8215 ICs are used. This is for obtaining four channels that is two channels from each IC. TA 8215 is an IC with power amplifier stages and preamplifier integrated inside it. Pins 7 and 19 are Vcc and pins 13 and 14 are ground of power amplifier stage. Vcc and ground pins should be connected to positive supply and ground respectively. Pin 9 is the Vcc of internal pre-amplifier and Pin 5 is its ground. Vcc is connected to positive supply and ground pin to ground through a 10 ohm resistor which separates input ground from common ground and this improves noise rejection.

In this circuit power supply decoupling is accomplished by 100 uF (C6 and C20) capacitor. High frequency stability in this circuit is achieved by the resistor network connected to the output line of each of the amplifier. Volume controller in each channel is the variable resistors of 10k (R3, R4, R12 and R13). The power supply required for this amplifier is single 12 V DC supply. The maximum output power delivered from each channel of this amplifier is 15 W to a 4 ohm speaker and hence the name 4×15 W power amplifier.

Circuit Diagram

4x15 Watt Power Amplifier Circuit

4x15 Watt Power Amplifier Circuit

Notes

  • For obtaining optimum sound quality assemble above circuit on a good quality PCB
  • The applications of this circuit have a wide range such as car audio systems, home theater systems, personal audio systems, public address systems etc.
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