TDA3050 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
TDA3050 Datasheet PDF : 4 Pages
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LM1875 20W 功率放大器
20 Watt / Channel Stereo Power Amplifier
Rod Elliott - ESP (From Design Notes from National Semiconductor)
Circuit Description
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. For those who want to build their own 'Gainclone' amplifier, this will certainly do
the job :-)
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. You
can also use the TDA3050 (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. 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.
Figure 1 shows the schematic - this is almost the same as in the application note (redrawn), and
with added RF protection at the input. Note that the speaker must return to the central 'star'
earth (ground) point. If connected to the amplifier's earth bus, you will get oscillation and/or
poor distortion performance.
Figure 1 - LM1875 / TDA3050 Power Amplifier Circuit Diagram (One Channel)
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). The amplifier must not be
operated at any gain less than 10 (20dB) as set by R4 and R5, as it will oscillate. In some cases,
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