Hi guys,
I am attempting to convert these Apex models to use IRFP9240/240 for the output. I believe both model uses the same circuit and to my knowledge no one build it yet. I let LTSpice do the calculations, transient response, squarewave test and stability test (Tian method), all passed. The only problem that I am encountering is the dc offset and THD at 20khz. Increasing the front end currents significantly increases THD at 20Khz.
All the mods that I've made so far are based on what I've read in this forum. I will appreciate any pointers and solutions on how to fix problems in the present circuit. I have attached the sim files for anyone to check. I am a total noob when it comes to CFA, the reason that I ve been doing this modification is because I only have the IRFP devices.
Thank you!
Albert
I am attempting to convert these Apex models to use IRFP9240/240 for the output. I believe both model uses the same circuit and to my knowledge no one build it yet. I let LTSpice do the calculations, transient response, squarewave test and stability test (Tian method), all passed. The only problem that I am encountering is the dc offset and THD at 20khz. Increasing the front end currents significantly increases THD at 20Khz.
All the mods that I've made so far are based on what I've read in this forum. I will appreciate any pointers and solutions on how to fix problems in the present circuit. I have attached the sim files for anyone to check. I am a total noob when it comes to CFA, the reason that I ve been doing this modification is because I only have the IRFP devices.
Thank you!
Albert
Attachments
Update;
I have revised the schematic, I decided to add a driver stage and regulate the front end. Current of the first input pair is now limited by 2 X 3k9 ohms resistor at 6ma. The THD at 20khz now drops to an acceptable level. I am still planning on wether to add degenerators or not..🤔 dc offset is still pretty high...
I have revised the schematic, I decided to add a driver stage and regulate the front end. Current of the first input pair is now limited by 2 X 3k9 ohms resistor at 6ma. The THD at 20khz now drops to an acceptable level. I am still planning on wether to add degenerators or not..🤔 dc offset is still pretty high...
