Skip to main content

4 watt audio amplifier circuit

I have recently included a page about AF amplifers for use with Homebrew rigs. In this I mentioned that I may include a practical one-watt circuit, complete with PCB foil and layout. Here it is, but I have taken the liberty of engineering it to provide 4-watts of AF output and with a frequency response almost suitable for Hi-Fi applications.

The circuit is very simple and incorporates darlington output transistors that will provide more than enough output current than is needed to drive a 3-ohm speaker. The gain may be pre-set for a variety of input levels, making it suitable for amplifying computer and cassette-deck Line-output levels. The input level is also suitable for use with the TDA7000 receiver. All components are easily available and I will shortly be making this project available as a kit. Naturally, the project will be built on a PCB which will also be available separately. Here is the first PCB, assembled and working.

The completed unit is 60mm x 75mm and only 30mm deep. The depth could be reduced to 10mm if the output capacitor is mounted at the speaker and the on-board electrolytics are mounted horisontally. Here are the typical performance figures that may be expected from the finished amplifer using a 3-ohm load with a 13.8-volt supply. I see no reason why the supply voltage cannot be increased a little to obtain more output power:
ParameterMinimumMaximumUnits
Supply voltage815volts
Output power-5.4Watts
I/P for full O/P304000mV (RMS)
Noise O/P no I/P-0.0005Volts RMS
Supply current (no-signal)-50mA
Supply Current (Full O/P)-1.9Amperes
3dB Frequency Response4234000Hertz
6dB Frequency Response2162000Hertz
Distortion at 2-watts-0.01% (Vgain=10)

No heatsinking is required for the output transistors when running at a modest output level with either speech or music. A small heatsink should be fitted to the two TIP41 transistors if running a constant tone level. The heatsink could be bolted directly to the TIP41s without electrical isolation if the heatsinks are not going to touch anything. A heatsink with a 15-square surface area is all that is required. Here is the circuit of the amplifer.


The gain of the amplifer is set by selecting the value of the feedback resistor (Rf) on the PCB. The value of Rf is equal to 4700 / (Vgain -1) where Vgain is the voltage gain required. 4-volts RMS is the full-output level. Here is a guide for selecting the resistor.


ValueVgainTypical use
2K2 3 1300mV RMS - High levels (Small radio speaker)
470R 11 400mV RMS - e.g. computer/tape-deck Line-out
100R 48 80mV RMS - e.g. from TDA7000 RX
33R 143 30mV RMS (e.g. from microphones)


The distortion and noise levels may increase at higher gain levels, but the test board was measured with Vgain = 10 and was driving a 3-ohm car Hi-Fi speaker. With higher-impedance speakers the frequency response will become wider but the output power will reduce a little. There was no trace of instability throughout the AF range and up to 150KHz so I thought it unncecssary to include a Zobel network. Incidentally, four-watts of AF will have the wife banging on the workshop walls, so do not underestimate QRP AF!

Comments

Popular posts from this blog

200W Subwoofer Amplifier Circuit

Circuit Description
Here is a circuit that uses a mosfet amplifier amplicable for subwoofer as the main booster, or the basis of this boosterAmplifier. Circuit which uses MOSFET Power Amplifier is powered by the output more than 200W Speaker 8 Ohm impedance. We also include a suitable power supply circuit with the use of MOSFETamplifier with 200W of power, not only of his course Schematic diagram for the layout design is also already there.
Amplifier Circuit Diagram
200W Mosfet Amplifier LAyout PCB
Regulator Circuit Diagram MOSFET AMPLIFIER Regulator PCB MOSFET amplifier

TDA7294 Audio Amplifier 2 x 80W

TDA7294 general description:
This circuit described here uses two cis tda 7294 for use in stereo (2 x 80Watts) or bridge mode (1x 180 Watts), to configure this setting just four jumpers. To facilitate mounting the circuit has power supply attached. The power is kind of simple symmetrical with a bridge rectifier 6A, and two large electrolytic capacitors , 10000μF the 22000μF/50v. This Power supply will for the two modules. The processor is recommended 22-0-22 to 28-0-28 / 5A, depending on the quality of the transformer is recommended at least 6 amps of current.


TDA7294 features:
High power performances with limited supply voltage level.Considerably high output power even with high load values (i.e. 16 Ohm).Rl= 8 Ohm, Vs = ±25V Pmax = 150 WRl=16Ohm, Vs = ±35V 
TDA7294 circuit diagram:

TDA7294 layout:TDA7294 pcb:

Datasheet for TDA7294:Download
Searches related to TDA7294 Audio Amplifier Circuits tda7294 bridge amplifier circuit ic tda7294 subwoofer tda7294 subwoofer schematic tda7294 single suppl…

TDA2030 Audio Amplifier 1 x40W

TDA2030 general description:    Although there are a number of hybrid output modules on the market, very few of them combine compactness with reasonable price and good performance. One of these few is SGS's used in the present amplifier. The design of the amplifier is straightforward: a power op-amp followed by two output transistors. The audio signal is applied to the non-inverting input of power op-amp IC1 TDA2030 via socket K1 and capacitor C1. The supply current to the IC varies in accordance with the input signal. Consequently, there will be a similarly varying voltage drop across resistors R6, R7, R8, and R9 since these are in the supply lines to the op-amp. As long as the current is lower than about 1A, the voltage drop across the resistors will be insufficient to switch on transistors T1 and T2. This means that outputs up to 2 W into 4 ohm are provided entirely by the op-amp. Once the output current exceeds a level of 1A, the transistors are on and contribute to the power …