I have an opa1622 evm board and really like it so i try to make a better headphone amp using opa1622. Inspire by the design of agdr, i come up with this but when i simulate the open loop gain for stability, it look incredibly unstable. The Aol*Beta ( pink line) cross 0db at phase margin <0. I need some advice on this, thanks.
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I don’t follow your schematic if are trying to parallel it. Here’s what I did with the OPa1688 and it works great. I have a new parallel 8 OPA1622 in the works - boards fabricated but not populated yet using same topology. You want an opamp to do voltage gain first then use parallel amps in buffer setup with 0dB gain. Have global feedback after the parallel buffers back to input stage.
http://www.diyaudio.com/forums/head...pa1688-low-thd-muscle-amp-10.html#post5494197
Like this:
http://www.diyaudio.com/forums/head...pa1688-low-thd-muscle-amp-10.html#post5494197
Like this:
The gain is provided by stage 1. Stage 2 provides current gain. This is the standard approach and gives great performance because each amp stage does one thing really well. Schematic as shown above has 12dB gain.
You don't understand what i said. Do you know what does compensation mean?
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Yes, I know what compensation is, you have C3 on global feedback loop. I have local compensation C111/C112 (actually using 33pF NP0) on the voltage gain stage alone.
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