Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Schematics and Layouts => Topic started by: kikback007 on May 20, 2020, 10:49:56 PM

Title: Who has Layout for Mosfet P. Amp?
Post by: kikback007 on May 20, 2020, 10:49:56 PM
Anyone? Im trying to build an amp in new approach. This time by using transistors. Maybe just 50w output is enough.
Title: Re: Who has Layout for Mosfet P. Amp?
Post by: Loudthud on May 22, 2020, 01:37:18 PM
This is an old design that was in an IR data book in the 80's. It doesn't have short circuit protection, but that can be added. You also need gate protection zeners for the output MOSFETs. I built one and it sounded good. You can get to 50W at 4 Ohms with +/- 25V rails.

Link: http://www.cieri.net/Documenti/Altri%20marchi/International%20Rectifier%20-%20Linear%20Power%20Amplifier%20Using%20Complementary%20HEXFETs%20(AN948).pdf

Edit: Attached below is the PCB layout from the Ap note article edited to show the components X-ray style over the etch.
Title: Re: Who has Layout for Mosfet P. Amp?
Post by: Loudthud on May 29, 2020, 02:04:18 AM
OK, I looked at the Ap Note and it's hard to follow. On the layout they provided there is no Q1 and two Q3's. The board side view doesn't line up with the component side view. There are also places where you need to add jumper wires that are not shown. So I built a new version and I'll show my layout sketch and the mods I did to the schematic. One additional mod I did was to add a capacitor to the input.

Most things I build are on a proto board with holes on 0.1 inch centers and copper pads on one side. To this I add eyelets from Keystone in three sizes. In some places you need to remove the copper pads because the pads cause shorts between eyelets. There are multiple ground wires that come off the power amp board to a star on the power supply board that I haven't built yet. I built the power amp board and got it running on my lab power supplies. Still might make some changes there. Another mod I allowed for is mixed mode feedback. There is an eyelet on the power amp board labeled IFB. That hooks to a low value resistor that goes between the low side of the speaker and ground. If you just want Voltage feedback, ground the IFB pin.

The attached schematic shows the short circuit protection and zener diodes on the MOSFETs.