Re: rectifier
- From: the Jackal <shooo@xxxxxxxxxxxx>
- Date: Mon, 02 Jan 2006 12:44:07 +0100
On Fri, 30 Dec 2005 08:47:09 -0600, "Abstract Dissonance"
<Abstract.Dissonance.hotmail.com> wrote:
>I was wondering if there is any type of circuits that use transistors in
>place of the diodes in a rectifier circuit?
>
>I was thinking that maybe one could use them in some way to smooth out a
>source by using some type of negative feedback or something... or maybe
>there could be some other use?
>
>Just wondering,
>
>Thanks,
>AD
>
Slow diodes can take even hundreds of microseconds to turn off though
popular fast turn off/on diodes like the 1N914 (used in computers) go
over their expected dc level upto even 0.5V for 10 to 20ns before the
diode turns on. Using the emitter base junction of BJTs like the
2N3904 as diodes negligible overshoot voltages are observed and turn
on times of 0.1ns are observed. Their leakage current is lower then
diodes too.
Disadvantage is they can withstand very low reverse voltages.
You'll find diode circuits that need speed in switchers , fast pulse
detectors and some voltage clamps.
In the field of audio I've heard of transistors used as diodes
exploiting the 2nd harmonics generated by BJTs to give
better/different sound outputs compared to diodes, but as you know
this may just be another audio myth!
.
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