Car Amplifiers » Amp circuits

LM386 circuit audio amplifier

amplifier — Sun, 22 Mar 2009 14:57:44 +0000

The LM386 circuit is a audio amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200.
The inputs are ground referenced while the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 milliwatts when operating from a 6 volt supply, making the LM386 ideal for battery operation.

LM386 circuit features

Battery operation

Minimum external parts

Wide supply voltage range: 4V–12V or 5V–18V

Low quiescent current drain: 4mA

Voltage gains from 20 to 200

Ground referenced input

Self-centering output quiescent voltage

Low distortion: 0.2% (AV = 20, VS = 6V, RL = 8Ω, PO = 125mW, f = 1kHz)

Available in 8 pin MSOP package

LM386 circuit applications

AM-FM radio amplifiers

Portable tape player amplifiers

Intercoms

TV sound systems

Line drivers

Ultrasonic drivers

Small servo drivers

Power converters

LM 386 series output power (Pout)

LM386N-1, LM386M-1 at VS = 6V, RL = 8ohms, THD = 10% is 250-325 mW

LM386N-3 at VS = 9V, RL = 8ohms, THD = 10% is 500-700 mW

LM386N-4 at VS = 16V, RL = 32ohms, THD = 10% is 700-1000 mW.

LM 386 amp circuit 20dB gain

LM386 Audio Amplifier with Gain = 20 and minimum part count.

LM386 audio amp 50dB gain

LM386 amplifier 200dB gain

LM 386 bass boost circuit

To make the LM 386 a more versatile audio amplifier, 2 pins ( pin 1 and 8 ) are provided for gain control. With pins 1 and 8 open the internal 1.35k resistor sets the gain at 20 (26 dB). If a capacitor is placed between pin 1-8, bypassing the built-in 1.35k resistor, the gain will go up to 200.

If a resistor is placed in series with the capacitor, the gain can be set to any value from 20 to 200. Gain control can also be done by capacitively coupling a resistor or FET transistor from pin 1 to the ground.

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Guitar amplifier 60W

amplifier — Fri, 06 Mar 2009 18:23:08 +0000

This is a medium power guitar amplifier is recommended especially for portable amplifier. The amplifier is a combination between a simple integrated audio driver, LM391-80 and a stage of output power designed contratemps with bipolar transistors.
Thermistor NTC, which is in temperature contact with output power transistors, allows to separate AO LM391 power stage when it heats too much.
The start of the thermal protection is at a NTC flow current NTC of approximately 200uA. Electrolytic condenser asure a “smooth start” to remove clicks that may occur when connecting the amplifier. It can happen that the protection can be too sensitive, in that case certain adjustments are admitted in the value of R4 or thermistor.
The standby current can be adjusted with P1. This potentiometer is initially 0 and then is adjusted to achieve a current of 50mA. Current can be increased up to 400mA if you want low distortions.
The power transistors are placed on the same side of printed circuit board, so that it can be mounted on a heatsink jointly with the thermistor. The heatsink must be large enough and have the thermal resistance of maximum 1⁰K / W.
L1 has 20 turns with 0.8mm emailed copper, coiled over R21. C9 is a ceramic capacitor.
Guitar amp specifications

frequency band (at 3dB/8Ω): 11Hz … 20kHz
THD at 1kHz: 0.006% at 1W/8&Omega/Ir = 400mA
THD at 1kHz: 0.02% at Ir = 400mA
THD at 1kHz: 0.02% at 65W/8&Omega/Uin = 873mV
THD at 1kHz: 0.006% at 80W/4&Omega/Uin = 700mV

Guitar amp circuit schematics

Guitar amplifier PCB layout

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2N3055 power amplifier circuits

amplifier — Sat, 14 Feb 2009 13:54:13 +0000

2N3055 is a silicon power transistor used mostly in amplifier and power supply circuits but it is designed for general–purpose switching and amplifier applications. 2N3055 transistor is packed in a TO-3 can, the maximum power rating is 115W, voltage 60V and 15 amp max with a beta gain of 20 to 70 at a collector current of 4A.
Its popularity is because it could dissipate 115W (full power) at a collector voltage of 60V and a collector current of 1.9A and still the case temperature did not exceeded 25⁰C.

So much talking… Let’s begin to present you some of the most used 2n3055 amplifier circuits available on the internet! This article is full with schematics, designs and probably new amplifier concepts.

2N3055 stereo amplifier 100W

A great stereo amplifier built with 2 x 2N3055 and 2 x MJ2955 power transistors, we cannot tell you if it is an 2 x 100W stereo amp or 2 x 50W…
First lets see the schematic (or diagram…)

Now lets look at the parts list

And finally the 2N3055 stereo amp pcb layout

Wait, there’s more!

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Small mini amplifier

amplifier — Thu, 12 Feb 2009 19:51:55 +0000

This audio amplifier is simple, small and easy to build. This mini amplifier can be a universal audio amplifier. It is built with an 741 IC, 2 transistors 2N1711 (2N1613, 2N3901, 2N3110) and 2N2904 (2N2905). With P1 you adjust the volume level and P2 controls the tone and can suppress high frequencies up to 20 dB. The output power in around 2 watts, input sensitivity is 100mV and at a power supply of 16V to 24V the current consumption is around 150mA.

Mini small amplifier circuit schematic

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TDA2030 amplifier circuit

amplifier — Wed, 11 Feb 2009 01:05:10 +0000

The TDA2030 amplifier circuit is a monolithic IC intended for use as a low frequency class AB amplifier. TDA2030 provides 14W output power (distorsions = 0.5%) at 14V/4Ω and at ± 14V or 28V is 12W/4Ω or 8W/8Ω. TheTDA2030 provides high output current and has very low harmonic and cross-over distortion which made it one of the most used IC in audio amplifiers designs.
TDA2030 can be connected in several ways to deliver different power ratings and characteristics, so we start with the simplest circuit design.

TDA2030 20W amplifier circuit diagram

TDA 2030 PCB layout

TDA 2030 parts placement

20W Assembly kit

TDA2030 circuit bridge 35W

In a bridge connection 2 x TDA2030 can deliver up to 35W on a 8Ω speaker.

BCL amplifier PCB

TDA 2030 40W with transistors

A great 40 W audio mono amplifier build with TDA2030, BD712 and BD711. The output power is 22W on 8 ohm speaker and 40W on 4 ohm.

TDA2030 40W amplifier schematic

PCB layout

TDA2030 pdf datasheet

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100W dumping amplifier circuit

amplifier — Tue, 10 Feb 2009 18:40:52 +0000

This dumping current amplifier particularity of this assembly consists of the fact that by introducing the four pasive components R2, R3, L and C, all harmful influences originating in the nonlinear behavior of the final stage are removed. It has 1 IC (741 or LF357), and 6 transistors, the final stage in equiped with TIP142 and TIP147 transistors.

The amplifier circuit presented here works after the current dumping principle, in class B operation and it delivers 99W on 4Ω speakers. Distortion coefficient is 0.006% at 1 kHz and 60W. If you have a device to measure properly, then the C3 can be replaced by a trimer of 22 pF and adjusted it to obtain a minimum rate distortion.
IC 741 may be replaced with a faster, for example LF357 when R4 and R7 are adjusted at the idle current of the IC, so that the final stage transistors are on the point to stop leading any idle current.

Dumping amplifier circuit diagram

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Headphones amplifier circuit

amplifier — Tue, 10 Feb 2009 18:08:46 +0000

This headphones amplifier circuit can deliver up to 1W on a 8Ω headsets. A stereo headset is connected, in generally, to an amplifier output through a voltage divider. This simple solving solution has 2 disavantages: the sound intesity cannot be adjusted independently from the speakers and the voltage divider lowers the attenuation factor for the headset which translates in bass altering.
This problem can be solved with a final stage amplifier similar to this, equiped with 2 power transistors, BD139 and BD140.

Headsets amplifier circuit diagram

So, this headphones amplifier can output a total power of 1 Watt, so the power supply must be designed for 300mA. The amplification factor depends on R4 and R5, its value is approximately equal to 11. With P2 we adjust the voltage in R12/R14 common point at half of the power supply. In idle mode the current through final transistors is 50 to 100 mA. Other rest currents can be attained by modifying the R8

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20W MOSFET amplifier

amplifier — Fri, 30 Jan 2009 16:53:04 +0000

This MOSFET amplifier uses two complementary MOSFETs (IRF9520 and IRF520) to deliver up to 20W into 8 Ω speaker. A TL071 op amp is used as an input amplifier. The MOSFETs should be heatsinked with a heatsink of better than 5⁰C/W capability. THD is less than 0.15% from 100Hz to 10KHz.

Mosfet amplifier circuit schematic

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50W audio amplifier 2N3055

amplifier — Thu, 29 Jan 2009 23:29:22 +0000

A very simple power amplifier circuit built with 741, 2N3053, 2N4037, 2N3055 and MJ2955 which deliver up to 50W on a 8Ω speaker.
If you want to amplify lower frequencies increase the 4.7uF capacitor from the audio input or decrease it if you want to favour higher frequencies.
Use a 3A symmetric power supply for mono application and a 5A for stereo power amplifiers. Please take good precaution when use this audio amplifier : do not shortcircuit the output or not connect speakers ! Always check twice !

2N3055 amplifier circuit diagram

50 watts amplifier pcb

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200 watts amplifier TDA2030

amplifier — Thu, 29 Jan 2009 23:09:33 +0000

TDA 2030 is produced by SGS Ates and is a complete audio amplifier. AB class of the final amplifier cand deliver up to 14W on 4 ohm at a +-14V power supply.
Connecting two TDA2030 thru cheap power transistors we can create a amplifier wich can deliver a higher power. With the components value from the schematic the total amplifier gain is 32 dB. The speaker can be 2 ohm instead of 4 ohm if we use the TIP transistors. With a proper designed power supply this audio amplifier can output 200W.
Active components:
IC1, Ic2 TDA 2030
T1, T3 = BD 250, TIP 36
T2,T4 = BD 249, TIP 35
D1 … D4 = 1N4001

200W audio amplifier circuit diagram

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