1W BTL Audio Amplifier circuit and explanation

The TDA8581(T) from Philips Semiconductors is a 1-watt Bridge Tied Load (BTL) audio power amplifier capable of delivering 1 watt output power into an 8-Wload at THD (total harmonic distortion) of 10% and using a 5V power supply. The schematic shown here combines the functional diagram of the TDA8551 with its typical application circuit. The gain of the amplifier can be set by the digital volume control input. At the highest volume setting, the gain is 20 dB. Using the MODE pin the device can be switched to one of three modes: standby (MODE level between Vp and Vp–0.5 V), muted (MODE level between 1 V and Vp–1.4 V) or normal (MODE level less than 0.5 V). The TDA8551 is protected by an internal thermal shutdown protection mechanism. The total voltage loss for both MOS transistors in the complementary output stage is less than 1 V.

Circuit diagram:

1 Watt BTL Audio Amplifier Circuit Diagram

Using a 5-V supply and an 8-W loudspeaker, an output power of 1 watt can be delivered. The volume control has an attenuation range of between 0 dB and 80 dB in 64 steps set by the 3-state level at the UP/DOWN pin: floating: volume remains unchanged; negative pulses: decrease volume; positive pulses: increase volume Each pulse at he Up/DOWN pin causes a change in gain of 80/64 = 1.25 dB (typical value). When the supply voltage is first connected, the attenuator is set to 40 dB (low volume), so the gain of the total amplifier is then –20 dB. Some positive pulses have to be applied to the UP/DOWN pin to achieve listening volume. The graph shows the THD as a function of output power. The maximum quiescent current consumption of the amplifier is specified at 10 mA, to which should be added the current resulting from the output offset voltage divided by the load impedance.

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Condenser Mic Audio Amplifier circuit Schematic with explanation

The compact, low-cost condenser mic audio amplifier described here provides good-quality audio of 0.5 watts at 4.5 volts. It can be used as part of intercoms, walkie-talkies, low-power transmitters, and packet radio receivers. Transistors T1 and T2 form the mic preamplifier. Resistor R1 provides the necessary bias for the condenser mic while preset VR1 functions as gain control for varying its gain. In order to increase the audio power, the low-level audio output from the preamplifier stage is coupled via coupling capacitor C7 to the audio power amplifier built around BEL1895 IC.

Circuit diagram:

Condenser Mic Audio Amplifier Circuit Diagram

BEL1895 is a monolithic audio power amplifier IC designed specifically for sensitive AM radio applications that delivers 1 watt into 4 ohms at 6V power supply voltage. It exhibits low distortion and noise and operates over 3V-9V supply voltage, which makes it ideal for battery operation. A turn-on pop reduction circuit prevents thud when the power supply is switched on. Coupling capacitor C7 determines low-frequency response of the amplifier. Capacitor C9 acts as the ripple-rejection filter.

Capacitor C13 couples the output available at pin 1 to the loudspeaker. R15-C13 combination acts as the damping circuit for output oscillations. Capacitor C12 provides the boot strapping function. This circuit is suitable for low-power HAM radio transmitters to supply the necessary audio power for modulation. With simple modifications it can also be used in intercom circuits.
Author: D. Prabakaran - Copyright: Electronics For You Mag

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LM4906 Boomer Audio Power Amplifier circuit and epxlanation

The well-known LM386 is an excellent choice for many designs requiring a small audio power amplifier (1-watt) in a single chip. However, the LM386 requires quite a few external parts including some electrolytic capacitors, which unfortunately add volume and cost to the circuit. National Semiconductor recently introduced its Boomer® audio integrated circuits which were designed specifically to provide high quality audio while requiring a minimum amount of external components (in surface mount packaging only). The LM4906 is capable of delivering 1 watt of continuous average power to an 8-ohm load with less than 1% distortion (THD+N) from a +5 V power supply. The chip happily works with an external PSRR (Power Supply Rejection Ratio) bypass capacitor of just 1 µF minimum.


In addition, no output coupling capacitors or bootstrap capacitors are required which makes the LM4906 ideally suited for cellphone and other low voltage portable applications. The LM4906 features a low-power consumption shutdown mode (the part is enabled by pulling the SD pin high). Additionally, an internal thermal shutdown protection mechanism is provided. The LM4906 also has an internal selectable gain of either 6 dB or 12 dB. A bridge amplifier design has a few distinct advantages over the single-ended configuration, as it provides differential drive to the load, thus doubling output swing for a specified supply voltage. Four times the output power is possible as compared to a single-ended amplifier under the same conditions (particularly when considering the low supply voltage of 5 to 6 volts).

Circuit diagram:

Boomer Audio Power Amplifier Circuit Diagram

When pushed for output power, the small SMD case has to be assisted in keeping a cool head. By adding copper foil, the thermal resistance of the application can be reduced from the free air value, resulting in higher PDMAX values without thermal shutdown protection circuitry being activated. Additional copper foil can be added to any of the leads connected to the LM4906. It is especially effective when connected to VDD, GND, and the output pins. A bridge configuration, such as the one used in LM4906, also creates a second advantage over single-ended amplifiers. Since the differential outputs, Vo1 and Vo2, are biased at half-supply, no net DC voltage exists across the load.

This eliminates the need for an output coupling capacitor which is required in a single supply, single-ended amplifier configuration. Large input capacitors are both expensive and space hungry for portable designs. Clearly, a certain sized capacitor is needed to couple in low frequencies without severe attenuation. But in many cases the speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 100 Hz to 150 Hz. Thus, using a large input capacitor may not increase actual system performance. Also, by minimizing the capacitor size based on necessary low frequency response, turn-on pops can be minimized.

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60 Watt Guitar Amplifier circuit and explanation

Bass, Treble, Harmonic modifier and Brightness controls
Output power: 40W into 8 Ohm and 60W into 4 Ohm loads

This design adopts a well established circuit topology for the power amplifier, using a single-rail supply of about 60V and capacitor-coupling for the speaker(s). The advantages for a guitar amplifier are the very simple circuitry, even for comparatively high power outputs, and a certain built-in degree of loudspeaker protection, due to capacitor C8, preventing the voltage supply to be conveyed into loudspeakers in case of output transistors' failure. The preamp is powered by the same 60V rails as the power amplifier, allowing to implement a two-transistors gain-block capable of delivering about 20V RMS output. This provides a very high input overload capability.

Amplifier circuit diagram:

60 Watt Guitar Amplifier Circuit Diagram

Amplifier parts:

R1__________________6K8 1W Resistor
R2,R4_____________470R 1/4W Resistors
R3__________________2K 1/2W Trimmer Cermet
R5,R6_______________4K7 1/2W Resistors
R7________________220R 1/2W Resistor
R8__________________2K2 1/2W Resistor
R9_________________50K 1/2W Trimmer Cermet
R10________________68K 1/4W Resistor
R11,R12______________R47 4W Wirewound Resistors
C1,C2,C4,C5________47µF 63V Electrolytic Capacitors
C3________________100µF 25V Electrolytic Capacitor
C6_________________33pF 63V Ceramic Capacitor
C7_______________1000µF 50V Electrolytic Capacitor
C8_______________2200µF 63V Electrolytic Capacitor (See Notes)
D1_________________LED Any type and color
D2________Diode bridge 200V 6A
Q1,Q2____________BD139 80V 1.5A NPN Transistors
Q3_____________MJ11016 120V 30A NPN Darlington Transistor (See Notes)
Q4_____________MJ11015 120V 30A PNP Darlington Transistor (See Notes)
SW1_______________SPST Mains switch
F1__________________4A Fuse with socket
T1________________220V Primary, 48-50V Secondary 75 to 150VA Mains transformer (See Notes)
PL1_______________Male Mains plug
SPKR______________One or more speakers wired in series or in parallel Total resulting impedance: 8 or 4 Ohm Minimum power handling: 75W



Preamplifier circuit diagram:

Guitar Preamplifier Circuit Diagram

Preamplifier parts:

P1,P2______________10K Linear Potentiometers
P3_________________10K Log. Potentiometer
R1,R2______________68K 1/4W Resistors
R3________________680K 1/4W Resistor
R4________________220K 1/4W Resistor
R5_________________33K 1/4W Resistor
R6,R16______________2K2 1/4W Resistors
R7__________________5K6 1/4W Resistor
R8,R21____________330R 1/4W Resistors
R9_________________47K 1/4W Resistor
R10_______________470R 1/4W Resistor
R11_________________4K7 1/4W Resistor
R12,R20____________10K 1/4W Resistors
R13_______________100R 1/4W Resistor
R14,R15____________47R 1/4W Resistors
R17,R18,R19_______100K 1/4W Resistors
C1,C4,C5,C6________10µF 63V Electrolytic Capacitors
C2_________________47µF 63V Electrolytic Capacitor
C3_________________47pF 63V Ceramic Capacitor
C7_________________15nF 63V Polyester Capacitor
C8_________________22nF 63V Polyester Capacitor
C9________________470nF 63V Polyester Capacitor
C10,C11,C12________10µF 63V Electrolytic Capacitors
C13_______________220µF 63V Electrolytic Capacitor
D1,D2____________BAT46 100V 150mA Schottky-barrier Diodes (see Notes)
Q1,Q3____________BC546 65V 100mA NPN Transistors
Q2_______________BC556 65V 100mA PNP Transistor
J1,J2___________6.3mm. Mono Jack sockets
SW1,SW2___________SPST Switches

Sensitivity:
35mV input for 40W 8 Ohm output
42mV input for 60W 4 Ohm output
Frequency response:
50Hz to 20KHz -0.5dB; -1.5dB @ 40Hz; -3.5dB @ 30Hz
Total harmonic distortion @ 1KHz and 8 Ohm load:
Below 0.1% up to 10W; 0.2% @ 30W
Total harmonic distortion @ 10KHz and 8 Ohm load:
Below 0.15% up to 10W; 0.3% @ 30W
Total harmonic distortion @ 1KHz and 4 Ohm load:
Below 0.18% up to 10W; 0.4% @ 60W
Total harmonic distortion @ 10KHz and 4 Ohm load:
Below 0.3% up to 10W; 0.6% @ 60W
Treble control:
+9/-16dB @ 1KHz; +12/-24dB @ 10KHz
Brightness control:
+6.5dB @ 500Hz; +7dB @ 1KHz; +8.5dB @ 10KHz
Bass control:
-17.5dB @ 100Hz; -26dB @ 50Hz; -28dB @ 40Hz

Notes:

• The value listed for C8 is the minimum suggested value. A 3300µF capacitor or two 2200µF capacitors wired in parallel would be a better choice.
• The Darlington transistor types listed could be too oversized for such a design. You can substitute them with MJ11014 (Q3) and MJ11013 (Q4) or TIP142 (Q3) and TIP147 (Q4).
• T1 transformer can be also a 24 + 24V or 25 + 25V type (i.e. 48V or 50V center tapped). Obviously, the center-tap must be left unconnected.
• D1 and D2 can be any Schottky-barrier diode types. With these devices, the harmonic modifier operation will be hard. Using for D1 and D2 two common 1N4148 silicon diodes, the harmonic modifier operation will be softer.
• In all cases where Darlington transistors are used as the output devices it is essential that the sensing transistor (Q2) should be in as close thermal contact with the output transistors as possible. Therefore a TO126-case transistor type was chosen for easy bolting on the heatsink, very close to the output pair.
• R9 must be trimmed in order to measure about half the voltage supply across the positive lead of C7 and ground. A better setting can be done using an oscilloscope, in order to obtain a symmetrical clipping of the output wave form at maximum output power.
• To set quiescent current, remove temporarily the Fuse F1 and insert the probes of an Avo-meter in the two leads of the fuse holder.
• Set the volume control to the minimum and Trimmer R3 to its minimum resistance.
• Power-on the circuit and adjust R3 to read a current drawing of about 30 to 35mA.
• Wait about 15 minutes, watch if the current is varying and readjust if necessary.

Author: www.redcircuits.com

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20W 12V Compact High-Performance Stereo Amplifier

Amplifiers which run from 12V DC generally don’t put out much power and they are usually not hifi as well. But this little stereo amplifier ticks the power and low distortion boxes. With a 14.4V supply, it will deliver 20 watts per channel into 4-ohm loads at clipping while harmonic distortion at lower power levels is typically less than 0.03%.

This is an ideal project for anyone wanting a compact stereo amplifier that can run from a 12V battery. It could be just the ticket for buskers who want a small but gutsy amplifier which will run from an SLA battery or it could used anywhere that 12V DC is available – in cars, recreational vehicles, remote houses with 12V DC power or where ever.

20W Stereo Audio Amplifier

Because it runs from DC, it will be an ideal beginner’s or schoolie’s project, with no 240VAC power supply to worry about. You can run it from a 12V battery or a DC plugpack. But while it may be compact and simple to build, there is no need to apologise for “just average” performance. In listening tests from a range of compact discs, we were very impressed with the sound quality.

Long-time readers might recall that we presented a similar 12V power amplifier design back in May 2001. It was a similar configuration to this one but it is now completely over-shadowed by the much lower distortion and greatly improved signal-to-noise ratio of this new design. In fact, let’s be honest: the previous unit is not a patch on this new design. It used two TDA1519A ICs which resulted in distortion figures above 1% virtually across the board and a signal-to-noise ratio of only -69dB unweighted.

20W Stereo Amplifier Circuit

However, by using the TDA­7377 power amplifier IC and making some other improvements, the THD (total harmonic distortion) of the new design is about 50 times better than the older unit (see performance graphs for details). The bottom line is that the THD under typical conditions is around just 0.03% or less. It is also able to deliver more output power due to the improved output transistors in the new power amplifier IC.

In addition, its idle power consumption is low – not much more than 1W. As a result, if you don’t push it too hard it will run cool and won’t drain the battery too quickly. And because the IC has self-protection circuitry, it’s just about indestructible. It will self-limit or shut down if it overheats and the outputs are deactivated if they are shorted.

Circuit diagram:

20W Stereo Amplifier Circuit Diagram

With a 12V supply, the largest voltage swing a conventional solid-state power amplifier can generate is ±6V. This results in a meagre 4.5W RMS into 4O and 2.25W RMS into 8O, without considering losses in the output transistors. Even if the DC supply is around 14.4V (the maximum that can normally be expected from a 12V car battery), that only brings the power figures up to 6.48W and 3.24W for 4O and 8O loads respectively – still not really enough.

There are three common solutions to this problem. The first is to boost the supply voltage using a switchmode DC converter. This greatly increases the cost and complexity of the amplifier but it is one way of getting a lot of power from a 12V supply. However, we wanted to keep this project simple and that rules out this technique.

Parts layout:

There are variations on the boosting method, such as the class H architecture used in the TDA1562Q IC featured in the Portapal PA Amplifier (SILICON CHIP, February 2003). It is able to achieve 40W/channel but with >0.1% THD. In that case, the amplifier output itself provides the switching for a charge pump. The second method is to lower the speaker impedance. Some car speakers have an impedance as low as 2O, which allows twice as much power to be delivered at the same supply voltage. However, we don’t want to restrict this amplifier to 2O loudspeakers.

Author: Nicholas Vinen - Copyright: Silicon Chip

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TDA1562Q 36 Watt Audio Power Amplifier circuit and explanation

It's based on a Philips class-H audio amplifier IC and can deliver 36W RMS OR 70W music power, all from a 13.8V supply. Our new Mighty Midget Amplifier can really pack a punch - around 36W RMS continuous into a 4-ohm load when using a 13.8V supply. However, it's the 70W of output power that it can deliver during dynamic (music) signal conditions that really make you sit up and take notice.

As can be seen from the photos and the circuit diagram, the Mighty Midget uses just a handful of parts. It's built on a PC board that measures just 104mm x 39mm but while its size may be modest, these's nothing at all modest about its power output. And the noise and distortion figures are pretty good too.

Circuit diagram:

At the heart of the circuit is the TDA1562Q IC, described by Philips as a "monolithic integrated Bridge-Tied Load (BTL) class-H high-efficiency power amplifier". It comes in a 17-pin "DIL-bent-SIL" plastic package and is not only designed for use in car audio and portable PA work but for mains applications as well; eg, mini/midi audio components and TV sound.

Parts layout:

PCB layout:

Performance:

Output power:----------------------36W RMS into 4R
Music power:-----------------------70W into 4R
Frequency response:---------------1dB down at 28Hz and 55kHz
Input sensitivity:-------------------130mV RMS (for 36W into 4?)
Harmonic distortion:----------------typically 0.2% (see graphs)
Signal-to-noise ratio:----------------95dB unweighted (22Hz to 22kHz)

Source: Silicon Chip March 2002

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latest Electro Harmonix Graphic Equalizer circuit schematic with explanation

This is the diagram od electro-harmonix graphic equalizer. You can specify the number of channels according to your needs. You just need to parallel the components: C1, C2, R1, an om-amp, Potensiometer and a 470 ohm resistor. The frequency to be boost decided by C1, C2 and R1. See the diagram for the C1, C2 and R1 combination versus the frequency.

For the op-amp, you can use op-amp IC TRX6221, NE5532 or LM833. Use regulated power supply and high quality components to obtain the quality audio output.

READ MORE - latest Electro Harmonix Graphic Equalizer circuit schematic with explanation