Help find the value of 2 caps

[Lingo]

Hi everyone,

This is the schematic for a Type 4 output drive section. Can someone please help me find the right values for these capacitors for IRF640Ns?

 

[newvirus2008]

That is not the drive for IRF640N, that is the feedforward capacitor that is supposed to cancel the base-emitter capacitance of 2N4401 BJT.

I would try 1nF to 10nF, while looking at the waveform on the scope.

 

[Lingo]

That is not the drive for IRF640N, that is the feedforward capacitor that is supposed to cancel the base-emitter capacitance of 2N4401 BJT.

I would try 1nF to 10nF, while looking at the waveform on the scope.

Thanks for your help 🙏
Could you also take a look at my other post for this AMP?

L

Thread 'Running Very HOT at idle'

2024-10-15 12:14 pm

Hello everyone,

I was repairing a Class D Type 4 amplifier with a simple output section failure, which had a dead FET on the low side. After removing that FET, I noticed it’s running very hot at idle with a 4-ohm load connected.

I replaced all the FETs, but the issue remains.

The gate drive is not perfect but not terrible either. However, the PWM output from the optocoupler on the low side looks pretty bad.

Additionally, the rails have some nasty noises.

Any help would be greatly appreciated. 🙏

*Sorry, I misplaced the LS and HS

• Lingo
• Replies: 4
• Forum: Class D

 

[newvirus2008]

...while looking at the waveform on the scope.

I meant the VCE of the first BJT.