Is there any place need to improve in this power amplifier

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I see a couple of things off hand with the power amp circuit. I am not a fan of FETs driving FETs, rather BJTs driving FETs or FETs driving BJT's. Base of Q114 could tie directly to GND eliminating R116. Local compensation of the output FETs is wrong. The zero (100R in series to 47pf) should be between the gate and drain, not in parallel with Cgs. There should be Zener protection for Vgs. Layout is important, at least the 1uf film decoupling cap should be physically close to the drain pins along with the gate Zobel. You want to reduce Ld and particularly Lg (lead inductances) to as little as possible. What is the purpose of R138? You might also add a resistor in series with C109 to form a zero for the global loop compensation.
 
I see a couple of things off hand with the power amp circuit. I am not a fan of FETs driving FETs, rather BJTs driving FETs or FETs driving BJT's. Base of Q114 could tie directly to GND eliminating R116. Local compensation of the output FETs is wrong. The zero (100R in series to 47pf) should be between the gate and drain, not in parallel with Cgs. There should be Zener protection for Vgs. Layout is important, at least the 1uf film decoupling cap should be physically close to the drain pins along with the gate Zobel. You want to reduce Ld and particularly Lg (lead inductances) to as little as possible. What is the purpose of R138? You might also add a resistor in series with C109 to form a zero for the global loop compensation.

R138Feedforward know?
 
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This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.