The Chipamp builds continue: The STMicroelectronics TDA7293 and TDA7294 power amplifiers
Both these audio chips use DMOS or double-diffused metal–oxide–
Power output is between 50 and 100W, depending on which chip is used, loading and power supply rail voltage.
The amplifiers can be run into 4 Ohm load, recommended +/-30V DC or 20V- 0-20V AC secondary.
THD is 0.1% 1kHz at 50W into 4Ohm. Slew rate is about 5V to 10V/uS, thermal protection cut out at 160 deg C. (Mute at 150 deg C).
Depending where these chips get purchased, prices vary from R100.00 upwards each, the 7293 being more expensive.
- TDA7293 application notes
- TDA7294 application notes
- The TDA7293 from Mantech is listed at approx R115.00 ex VAT,
- Protec Electronics in Durban lists the TDA7294 at just over R50.00 incl. (this must be old pricing).
Both these audio chips are used in circuits where the configuration calls for bridging and parallel. Some of the output powers are absolutely ludicrous, anything from 200W for one chip into 2 Ohms to 700W into 4 Ohms. This is not going to happen folks. You either bridge and keep to 8 Ohms using supply rail voltages designed for this or you parallel and drive higher outputs into loads smaller than 4 Ohms. Or of course (not a good idea), you parallel and bridge and drive huge currents through a 1 Ohm load. But never 700W into 4 Ohms.
Functional diagrams from the application notes:
Just like most chip amps these devices use a minimal of external components:
The application notes are very good, the circuit above is included as well as a PCB layout. The more common >100W into 8 Ohms is shown below, a bridged mode amplifier using the TDA7294 but the more common 7293 can be used as well, just keep to below spec limits.
Bridging amplifier chips is a very common configuration but DIYers need to know the limitations. As in the circuit above, running load values below 8 Ohms without the additional cooling and PSU capacity is inviting trouble.