diyAudio Forums Archive > Top > Amplifiers > Class D Need Suggestions for Class D Inductors - Click HERE for Original Thread Tubist Hi Guys. I have an opportunity to run a board using AD1994 Analog Class D from ADI. Basically I am doing another (not audio) 2 layer digital board and using the excess PCB to run the AD1994 design. My main board is reflow process and I am running the AD1994 board concurrently "for testing purposes" to account to my company for the usage. ;) Most of the components selection is very straight forward. However, I need suggestions for off the shelf inductors (shielded) suitable for this application. I will also appreciate suggestions on what specs to look for in a suitable class D amp inductors. I am designing the AD1994 in mono-mode, which can go 80W into 2 Ohms. Any suggestions and ideas will be welcome. Thanks in advance!! rogs I've used these before - http://www.farnell.com/datasheets/62120.pdf - seem to be OK for low/ medium power class D applications. Gorilla I have used Coilcraft (http://www.coilcraft.com/) to get samples before. They seem pretty good. In terms of inductor selection, I wouldn't use ferrite based coils, especially in a non-post-filter feedback design. The more non-linear your B-H curve, the more THD. LineSource What is the formula to calculate the size of the inductor you need, say for a 1 ohm load instead of 8 ohm, at x-watts, at y-clock_freq? Tubist quote: Originally posted by Gorilla I have used Coilcraft (http://www.coilcraft.com/) to get samples before. They seem pretty good. In terms of inductor selection, I wouldn't use ferrite based coils, especially in a non-post-filter feedback design. The more non-linear your B-H curve, the more THD. Hi. Thanks for the suggestion, but I am primary concerned with the EMI from a air-core inductor, even for domestic use, as my setup, I do have a radio as my source. In actual application, would the use of a air-core inductor be really bad and interfere with other equipment performance? If we are to put a metal shield around an air-core, would it help? Thanks for any answers :) zilog quote: Originally posted by LineSource What is the formula to calculate the size of the inductor you need, say for a 1 ohm load instead of 8 ohm, at x-watts, at y-clock_freq? Read this link -> http://www.qsl.net/xq2fod/Electron/Magnet.html I consider the output inductor a DC choke, you should use gapped ferrite or iron powder for linearity. Also design for a flux density of no more than say 0.2T at peak current to avoid distortion.

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