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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: Re: Tektronix Cascomp and decendants posted by Steve Eddy on May 19, 2003 at 22:03:24:
""Tube technology allows electrons to travel through a vacuum which causes no storage or memory effect, but solid-state amplifiers use silicon components which keeps the trace of electrons flux that have gone through.""What they are talking about here is excess minority carriers, not thermal effects. The carrier density in the base of a bipolar transistor depends only on the present level of injection under the quasi-static assumption, but a rapid decrease in base drive requires the excess carriers to recombine (or be swept out by the field) since they are no longer needed to support the current. Until they go away, they affect the interelectrode capacitances of the transistor and the phase margin of the amplifier using it for gain.
Long ago, when people tried to build fast computers out of big transistors, they resorted to gold doping to kill the base lifetime so this recombination would happen more quickly. Progress in manufacturing technology allows smaller features and more precise control of the doping profile, so this storage is no longer a problem for digital logic. Circuit tricks to stabilize the injection may or may not be useful in audio. Note that this is not the small-signal cutoff frequency problem, but primarily affects large-signal devices.
You can read about this in _Physics of Semiconductor Devices_, 2nd Edition, S.M. Sze, Wiley-Interscience, 1981.
Similar considerations hold for majority carrier devices (JFETs and MOSFETs), since interelectrode capacitances have to be charged and discharged to reach electrostatic equilibrium.
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Follow Ups
- Minority carrier lifetime - Leisure7 23:41:17 05/19/03 (8)
- Re: Minority carrier lifetime - jneutron 10:08:21 05/20/03 (6)
- Re: Minority carrier lifetime - john curl 11:51:54 05/20/03 (5)
- Re: Minority carrier lifetime - jneutron 12:38:47 05/20/03 (4)
- Re: Minority carrier lifetime - john curl 15:35:35 05/20/03 (3)
- Gold diggers... - Leisure7 14:53:47 05/21/03 (1)
- Re: Gold diggers... - Scott Frankland 21:47:34 05/22/03 (0)
- Re: Minority carrier lifetime - Steve Eddy 15:55:27 05/20/03 (0)
- Re: Minority carrier lifetime - Steve Eddy 01:48:31 05/20/03 (0)
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