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Old 22nd Feb 2021, 3:51 pm   #17
Radio Wrangler
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Default Re: Sugden preamp WAL AC Farnell.

Quote:
Originally Posted by Craig Sawyers View Post
(In addition, one of those transistors looks like a Ferranti E-line, now made by Diodes Inc. One of the secrets of low voltage noise designs are the E-line devices)
To most users, Ferranti had evolved some quite outstanding transistors with particularly good current handling for their package size. Thismade them great for motor control... EG switching to drive stepper motors and bridges for switching direction of DC brushed motors.

This was done by designing in excellent current sharing mechanisms and low base-spreading resistance.

Coincidentally, this also made them rather good for low noise capabilities in low impedance environments. It took a while for this to be recognised, but it's real.

Low noise people designing dynamic microphone inputs eventually found that Rohm made a range of low spreading resistance transistors for the motor drive market, and that these parts were about the best for their work. Of course, Rohm obsoleted them when they saw the motor market drop off as it changed to MOSFETs and IGBTs.

Who'd have thought that tough motor drive transistors would have a sideline in the most delicate applications?

David
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