# Oscillation in Class D amp design

I am building a class d amp circuit with base design from Great Scott's Class D amp which is found here. I am trying to build and simulate the circuit in LTSpice with difference being I won't be using MOSFET Driver IC and will be inverting the signal and feeding it to another half bridge to make a full bridge amplifier.

Here is the Circuit and simulation files:- https://drive.google.com/drive/folders/1_B0tQIh58_niOk3M4CdICHCKTr6wPS08?usp=sharing

I am experiencing some wierd oscillation at the start of the circuit for a few milli-seconds. Can anyone point out the reason and/or a fix. Will the circuit get damaged if I build it as it is?

Here is the output of the simulation:-

The oscillation occurs on both of the half bridge after passing through lc filter. The blue line is the load resistor current. (In reality, the current would be half tho. I am using 1 ohm load in design while in reality I have 2 ohm subwoofer)

Also note, the circuit will only be used for sub frequencies, so don't point out that voice will get lower as frequency increases and also, it gets distorted at higher frequencies.

• I don't see anything weird - what do you see that is weird? Also what node is V(n009)? – Andy aka Dec 14 '20 at 11:49
• If You want to build and use class d amp - really go for driver chip. This will save You a lot of burned transistors and time – fifi_22 Dec 14 '20 at 13:44
• So, should I go for dual IR2110/2113? Also, as suggested in the answer below, do they add a dead-time? – Saksham gupta Dec 14 '20 at 13:49
• Adding to the comment from @fifi_22 , no 555 should be used in a class D that's about to be built in real life, unless you want to study the circuit, or play with it. Certainly not for a 90 V (bridge) and a 1 $\Omega$ load. 555 or not, that's exaggerated. Not to mention you're simulating with generic BJTs, and there is no feedback, no linearizing. It really looks like you're in for some magic smoke. – a concerned citizen Dec 14 '20 at 15:13
• Would a 555 cause problems? Stability? Any alternative? I shoud be able to simulate with any bjt that has HFE > 100 and current capability of 500ma+. I know there's no feedback but I won't really be powering it at 90V (60V in real) also I have mentioned in my question that only sub frequencies will be used so I am not concerned about feedback. and that I will be using 2 ohm load. – Saksham gupta Dec 14 '20 at 15:57