For my PCB, I was planning on just using a DC power adapter to power this amplifier circuit but I'm new to electronics, so I don't know if a DC adapter will work. Any assistance would be appreciated. This is from the TI LM1875 datasheet. https://www.ti.com/lit/ds/symlink/lm1875.pdf
It will if you can find an adapter with high enough voltage and current. For example, for a mono amplifier, a 30 V, 1.6 A adapter should suffice to get an output power of 10 W into 8 ohm. 30 V, 1 A will do if the adapter can deliver repetitive current peaks above 1 A of a couple of milliseconds long, as long as the average stays below 1 A.
Got it, in addition, as far as schematic goes, that adapter part will attach where VCC is correct?
Yes, and watch the polarity of the supply, and of all the capacitors, if they are marked.
Don't forget the heat sink.
Don't forget the heat sink.
The heatsink is not usually on the schematic, since it is technically not an electrical part.
The power device LM1875, with thermal grease, is mounted on it.
The heat sink size depends on the power you want, but it is often much larger than the pcb itself.
Here's a kit version with sink. You can see the typical size of the sink.
https://www.aliexpress.us/item/2251832711766830.html
The power device LM1875, with thermal grease, is mounted on it.
The heat sink size depends on the power you want, but it is often much larger than the pcb itself.
Here's a kit version with sink. You can see the typical size of the sink.
https://www.aliexpress.us/item/2251832711766830.html
Last edited:
you need to create a virtual ground if you want to use single rail...an equal value resistor divider is all it takes..
I built this 1875 singleton and powered it with a general purpose 19Vdc laptop supply. It sounded good but there is a nasty turn on thump to charge C6. I reduced the thump by replacing C3 10uf with a 220uf.
I'm planning on using a 3A 20V DC adapter to power the LM1875, what heatsink would you recommend for this?
100uf is too small, use at least 470-1000uf for C7. More isn't recommended if your DC adapter is based on SMPS. If you're concern about accidental power supply polarity swap you can add a discrete diode in series with the VCC. You can also try a relay based delay circuit at the output to avoid turn on/off thump. With 20vDC power supply i think a heatsink of 1°C/W thermal resistance is enough for stereo setup.