Telephone AmplifierLF351 and TBA820M

Amplifier description:

This circuit TDA820M Mini Amplifier 2W+2W. Supply Volt 12V, Easy to build and Low cost. If you want mini amplifier circuit , as a result do not be defeated certainly. The sound will a little 2W+2W just but enough with 6 sizes are inch 8ohm loudspeakers. as a result still have a voice good loud the moderately. Request friends have fun the circuit amplifies this miniature please yes.

Circuit diagram:

PCB layout:

In Mono style a few parts and very cheap!
TBA820 mini AUDIO AMPLIFIER 1.2W
Here is Circuit Mini power amplifier low watt (1.2W Only). IN circuit have IC TBA820,it old IC Audio amp.

 

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Low Power Wireless Audio Power Amplifier

     Using this low-cost project one can reproduce audio from TV without disturbing others. It does not use any wire connection between TV and Loud Speaker. In place of a pair of wires, it uses invisible infra-red light to transmit audio signals from TV to Loud speakers, Without using any lens a range of up to 6 meters is possible. Range can be extended by using lenses and reflectors with IR sensors comprising transmitters and receivers.

     IR transmitter uses two-stage transistor amplifier to drive two series-connected IR LEDs. An audio output transformer (T1) is used (in reverse) to couple audio output from TV to the IR transmitter. Transistors Q1 and Q2 amplify the audio signals received from TV through the audio transformer. Low impedance output windings (lower gauge or thicker wires) are used for connection to TV side while high-impedance windings are connected to IR transmitter. This IR transmitter can be powered from a 9V mains adapter or a 9V battery. Red LED (D1) in transmitter circuit functions as a Zener diode (0.65V) as well as supply-on indicator.

Transmitter diagram:

Wireless Audio Power Amplifier Transmitter Circuit Diagram

Receiver's operation:

      IR receiver uses popular op-amp IC µA741 and audio-frequency amplifier IC LM386 along with phototransistor L14F1 (Q3) and some discrete components. The sound generated by TV set is transmitted through IR LEDs, received by phototransistor Q3 and fed to pin 2 of IC µA741 (IC1). Its gain can be varied using potmeter P2. The output of IC µA741 is fed to IC LM386 (IC2) via capacitor (C7) and potmeter P3. The sound produced is heard through the receiver’s loudspeaker. Potmeter P3 is used to control the volume of loudspeaker SPKR (8-ohm, 1W).

Receiver diagram:

Wireless Audio Power Amplifier Transmitter Circuit Diagram

Parts:

P1 = 10K

P3 = 10K

P2 = 1M

R1 = 4.7K

R2 = 22K

R3 = 100R

R4 = 10R-1W

R5 = 10K

R6 = 10K

R7 = 15K

R8 = 15K

R9 = 100K

R10 = 680R-1W

R11 = 1K

R12 = 10R-1W

C1 = 220uF-25V

C2 = 220uF-25V

C3 = 10uF-25V

C4 = 220uF-25V

C5 = 220uF-25V

C6 = 100nF-63V

C7 = 100nF-63V

C8 = 100nF-63V

C9 = 100nF-63V

D1 = Red LED

D2 = IR LEDs

D3 = IR LEDs

Q1 = BC547

Q2 = BD140

Q3 = L14F1

IC1 = uA741 Opamp

IC2 = LM386

J1 = Audio input Jack

T1 = Audio Transformer

SPKR = 1W-8ohm

LM4910 Stereo Headphone Amplifier

Circuit description:    

      LM4910 belonging to the Boomer series of National Semiconductors is an integrated stereo amplifier primarily intended for stereo headphone applications. The IC can be operated from 3.3V ans its can deliver 0.35mW output power into a 32 ohm load. The LM4910 has very low distortion ( less than 1%) and the shutdown current is less than 1uA. This low shut down current makes it suitable for battery operated applications. The IC is so designed that there is no need of the output coupling capacitors, half supply by-pass capacitors and bootstrap capacitors. Other features of the IC are turn ON/OFF click elimination, externally programmable gain etc.

Circuit diagram:  

     Circuit diagram of the LM4910 stereo headphone amplifier is shown above.C1 and C2 are the input DC decoupling capacitors for the left and right input channels. R1 and R2 are the respective input resistors. R3 is the feed back resistor for left channel while R4 is the feed back resistor for the right channel. C3 is the power supply filter capacitor. The feedback resistors also sets the closed loop gain in conjunction with the corresponding input resistors.

The IC is available only in SMD packages and care must be taken while soldering. 

The circuit can be powered from anything between 2.2V to 5V DC. 

The load can be a 32 ohm headphone. 

Absolute maximum supply voltage is 6V and anything above it will destroy the IC. 

A logic low voltage at the shutdown pins shut downs the IC and a logic high voltage at the same pin activates the IC. Original aritcle sourse circuitsproject.com

Battery-powered Headphone Amplifier

Description:

    

   Some lovers of High Fidelity headphone listening prefer the use of battery powered headphone amplifiers, not only for portable units but also for home "table" applications. This design is intended to fulfil their needs and its topology is derived from the Portable Headphone Amplifier featuring an NPN/PNP compound pair emitter follower output stage. An improved output driving capability is gained by making this a push-pull Class-B arrangement. Output power can reach 100mW RMS into a 16 Ohm load at 6V supply with low standing and mean current consumption, allowing long battery duration. The single voltage gain stage allows the easy implementation of a shunt-feedback circuitry giving excellent frequency stability.

Battery-powered Headphone Amplifier Circuit diagram

     For a Stereo version of this circuit, all parts must be doubled except P1, SW1, J2 and B1.  Before setting quiescent current rotate the volume control P1 to the minimum, Trimmer R6 to maximum resistance and Trimmer R3 to about the middle of its travel.  Connect a suitable headphone set or, better, a 33 Ohm 1/2W resistor to the amplifier output.  Switch on the supply and measure the battery voltage with a Multimeter set to about 10Vdc fsd.  Connect the Multimeter across the positive end of C4 and the negative ground.  Rotate R3 in order to read on the Multimeter display exactly half of the battery voltage previously measured.  Switch off the supply, disconnect the Multimeter and reconnect it, set to measure about 10mA fsd, in series to the positive supply of the amplifier.  Switch on the supply and rotate R6 slowly until a reading of about 3mA is displayed.  Check again the voltage at the positive end of C4 and readjust R3 if necessary.  Wait about 15 minutes, watch if the current is varying and readjust if necessary.  Those lucky enough to reach an oscilloscope and a 1KHz sine wave generator, can drive the amplifier to the maximum output power and adjust R3 in order to obtain a symmetrical clipping of the sine wave displayed. 

Technical data:

Output power (1KHz sinewave):

16 Ohm: 100mW RMS

32 Ohm: 60mW RMS

64 Ohm: 35mW RMS

100 Ohm: 22.5mW RMS

300 Ohm: 8.5mW RMS

Sensitivity: 160mV input for 1V RMS output into 32 Ohm load (31mW)

200mV input for 1.27V RMS output into 32 Ohm load (50mW)

Frequency response @ 1V RMS:

flat from 45Hz to 20KHz, -1dB @ 35Hz, -2dB @ 24Hz

Total harmonic distortion into 16 Ohm load @ 1KHz:

1V RMS (62mW) 0.015% 1.27V RMS (onset of clipping, 100mW) 0.04%

Total harmonic distortion into 16 Ohm load @ 10KHz:

1V RMS (62mW) 0.05% 1.27V RMS (onset of clipping, 100mW) 0.1%

Unconditionally stable on capacitive loads

Class-A Headphone Amplifier

     This circuit is derived from the Portable Headphone Amplifier featuring an NPN/PNP compound pair emitter follower output stage. An improved output driving capability is gained by making this a push-pull Class-A arrangement. Output power can reach 427mW RMS into a 32 Ohm load at a fixed standing current of 100mA. The single voltage gain stage allows the easy implementation of a shunt-feedback circuitry giving excellent frequency stability.

     The above mentioned shunt-feedback configuration also allows the easy addition of frequency dependent networks in order to obtain an useful, unobtrusive, switchable Tilt control (optional). When SW1 is set in the first position a gentle, shelving bass lift and treble cut is obtained. The central position of SW1 allows a flat frequency response, whereas the third position of this switch enables a shelving treble lift and bass cut.

     Before setting quiescent current rotate the volume control P1 to the minimum, Trimmer R6 to zero resistance and Trimmer R3 to about the middle of its travel. 

Connect a suitable headphone set or, better, a 33 Ohm 1/2W resistor to the amplifier output. 

Connect a Multimeter, set to measure about 10Vdc fsd, across the positive end of C5 and the negative ground.  Switch on the supply and rotate R3 in order to read about 7.7-7.8V on the Multimeter display. 

Switch off the supply, disconnect the Multimeter and reconnect it, set to measure at least 200mA fsd, in series to the positive supply of the amplifier.  Switch on the supply and rotate R6 slowly until a reading of about 100mA is displayed.  Check again the voltage at the positive end of C5 and readjust R3 if necessary.  Wait about 15 minutes, watch if the current is varying and readjust if necessary.

P1          : 22K  Dual gang Log Potentiometer 
R1          : 15K 
R2          : 220K
R3          : 100K
R4          : 33K 
R5          : 68K 
R6          : 50K 
R7          : 10K 
R8,R9       : 47K 
R10,R11     : 2R2 
R12         : 4K7
R13         : 4R7
R14         : 1K2
R15,R18     : 330K
R16         : 680K
R17,R19     : 220K
R20,R21     : 22K
C1,C2,C3,C4 : 10µF/25V 
C5,C7       : 220µF/25V
C6,C11      : 100nF
C8          : 2200µF/25V
C9,C12      : 1nF
C10         : 470pF
C13         : 15nF
D1          : LED
D2,D3       : 1N4002 
Q1,Q2       : BC550C 
Q3          : BC560C  
Q4          : BD136   
Q5          : BD135   
IC1         : 7815
T1          : 15CT/5VA Mains transformer
SW1         : 4 poles 3 ways rotary Switch 
SW2         : SPST slide or toggle Switch

Mobile Car Stereo Player TDA1554

     Using a mobile phone while driving is dangerous. It is also against the law. However, you can use your mobile phone as a powerful music player with the help of a stereo power amplifier. This does away with the need of a sophisticated in-dash car music system. Most mobile phones have a music player that offers a number of features including preset/manual sound equalisers. They have standard 3.5mm stereo sockets that allow music to be played through standard stereo headphones/sound amplifiers. Nokia 2700 classic is an example.


Mobile Car Stereo Player Circuit Diagram

     A car audio amplifier with 3.5mm socket can be designed and simply connected to the mobile phone output via a shielded cable with suitable connectors/jacks (readymade 3.5mm male-to-male connector cable is a good alternative). Fig. 1 shows the circuit of car stereo player. It is built around popular single-chip audio power amplifier TDA1554Q (IC1). The TDA1554Q is an integrated class-B power amplifier in a 17-lead single-in-line (SIL) plastic power package.

     IC TDA1554Q contains four 11W identical amplifiers with differential input stages (two inverting and two non-inverting) and can be used for single-ended or bridge applications. The gain of each amplifier is fixed at 20 dB. Here it is configured as two 22W stereo bridge amplifiers. The amplifier is powered from the 12V car battery through RCA socket J2. Diode D1 protects against wrong-polarity connection. LED1 indicates the power status.

Stereo Jack :



(a) 3.5mm stereo socket and (b) 3.5mm Stereo Jack

     Connect stereo sound signal from the 3.5mm headset socket of the mobile phone to audio input socket J1. When you play the music from your mobile, IC1 amplifies the input. The output of IC1 is fed to speakers LS1 and LS2 fitted at a suitable place in your car. Electrolytic capacitor C5 connected between pin 4 of IC1 and GND improves the supply-voltage ripple rejection. Components R2 and C4 connected at mute/standby pin (pin 14) of IC1 eliminate the switch on/off plop. The circuit is quite compact. A good-quality heat-sink assembly is crucial for IC1. Fig. 2 shows the stereo socket and stereo jack.

Proposed enclosure

     Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Small dimensions of the power amplifier make it suitable for being enclosed in a plastic (ABS) case with vent holes. Signal input socket, speaker output terminals, on/off switch, indicator, fuse holder and power supply socket are best located on the front panel of the enclosure as shown in Fig. 3.
Author : T.K. Hareendran - Copyright : EFY

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