Power amplifier electronic circuits-tube audio rf amplifiers

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

April 21st, 2010

Automatic Cooler Fan Circuit for Amplifiers

Circuit Description

Automatic cooler fan for amplifiers is a circuit introduced for the purpose of saving power in amplifier circuits. This circuit switches ON and switches OFF the cooler fan of heat sink according to its temperature. The cooler fan will turn ON when heat sink temperature exceeds a certain value and will turn OFF temperature become lower than a certain value. Automatic cooler circuit does it always so that effective working of cooling fan occurs and that saves power.

In this circuit thermistors are used as temperature sensors. Here negative temperature coefficient thermistor (NTC) is used. NTC means as temperature increases the resistance of NTC thermistor decreases. Resistor R2 in circuit diagram is an NTC thermistor. Here LM311 IC is used as a comparator which is having an inverting (pin 3) and non-inverting (pin 2) input pins. The junction of R1 and R2 is connected to pin 3. At pin 2 a reference voltage is given using resistor R3. The comparator compares voltage at its inverting and non-inverting terminals. When voltage at inverting terminal becomes less than that at non inverting terminal, the output of comparator becomes high. This will turn ON transistor Q1 which triggers relay and cooler fan will turn ON. Fan will be turned off when voltage at inverting terminal becomes higher than non-inverting terminal.

12 V DC supply is used as power supply in this circuit. The relay K1 can be a 12V, 200 ohm, SPST relay. Calibration of this circuit can be done by adjusting R3.

Circuit Diagram

Automatic Cooler Fan Circuit for Amplifiers

Automatic Cooler Fan Circuit for Amplifiers

Notes

  • Use Vero board to assemble components.
  • Diode D1 is a freewheeling diode.
  • LED D2 acts as an indicator, it will glow when fan is ON.
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.
April 21st, 2010

Simple Stereo Amplifier

Circuit Description

The circuit of 2×32 Watts stereo amplifier consists of two channels. In both the channels the central component is the IC TDA 2050 V developed by ST Microelectronics. The audio input signal is given to each of the channels in non-inverting input pin of IC TDA 2050V. For decoupling purpose, capacitor 1 uF (C1 and C8) is connected so that input can be given through it as shown in the circuit diagram.

The gain of the amplifier in each channel is determined by the resistors 22k (R1 and R5) and 680 ohm (R2 and R6). The value of gain is the ratio of 22K and 680 ohm. To improve the frequency response of the amplifier, a network called Zobel network is used in this circuit. Here the Zobel network is the combination of 2.2 ohm (R4 and R8) resistor and 0.47 uF (C3 and C14) capacitor that are connected in series between the amplifier output and ground in both the channels. By the effect of Zobel network, impedance of the speaker appears as resistive load and that improves frequency response of the amplifier.

The central part of the circuit TDA 2050V IC is an integrated monolithic 32 watt class B audio amplifier. It has some extra features like short circuit protection, low distortion, thermal protection etc. and it is available in Pentawatt package. Proper heat sink should be provided for this IC in PCB. Power supply required for this circuit is 18 V DC dual supplies. In order to get maximum output power, the input required is 200m Vpp RMS. Volume control is done by 10K pots connected at input lines. Assembling this circuit on a good quality PCB will give the desired output.

Circuit Diagram

Simple stereo amplifier circuit

Simple stereo amplifier circuit