Distortion and Magic Resistor Ratios

jorgen.bergfors at idg.se jorgen.bergfors at idg.se
Tue Mar 14 14:25:04 CET 2000

>Magic Numbers: The 100K/220 ohm input structure
>for the CA3080 is practically religious. But simple
>math shows a +22 DC mv excursion for a +10DCV input.
>Or 44 mv p-p for a +/-10p-p for 20dB input.

I measured the distortion on an Audio Precision System 2.
With 100k/220R you have 5 dB headroom above 10V p-p for 1% dist.

>LM13x00: Magic number is 220K/1K for 100mv p-p at 1% distortion and Id at 1 >ma (15K from +15v) into the current mirrors.

I used 15K/500R This gives 8 dB headroom at 10V p-p and 1% dist. The diodes were biased with 12k to +15V


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