The most common capacitive load is the speaker cable itself, and 'audiophile' leads are often worse than standard grade cables in this respect. In some cases, an inductor may be needed in series with the output to prevent instability with capacitive loads (10 turns of 0.5mm wire wound around a 10 Ohm 1W resistor). The amplifier must not be operated at any gain less than 10 (20dB) as set by R4 and R5, as it will oscillate. Voltage gain is 27dB as shown, but this can be changed by using a different value resistor for the feedback path (R4, currently 22k, between pins 2 and 4). If connected to the amplifier's earth bus, you will get oscillation and/or poor distortion performance.įigure 1 - LM1875 / TDA2050 Power Amplifier Circuit Diagram (One Channel) Note that the speaker must return to the central 'star' earth (ground) point. The amp is also remarkably simple to build - if you have a PCB! These ICs are a cow to wire on Veroboard - it is possible, but results are unpredictable.įigure 1 shows the schematic - this is almost the same as in the application note (redrawn), and with added RF protection at the input. You can also use the TDA2050 (from SGS-Thompson), which has almost identical performance and (remarkably) the same pinouts! As it turns out, the amp in the NS application circuit is pretty good, as is the (very similar) one from SGS.

This project (unlike most of the others, but in a similar vein to Project 19) is based almost directly on the typical application circuit in the National Semiconductor specification sheet. For those who want to build their own 'Gainclone' amplifier, this will certainly do the job :-)

There are many instances where a simple and reliable power amplifier is needed - rear and centre channel speakers for surround-sound, beefing up the PC speakers, low powered tweeter amplifier, etc.

Skema power ampli 170watt