Any potential advantages Shottkys may have in switching are lost if used for biasing. As the forward voltage drop is less than other diodes you can probably get more accurate bias voltages by stacking them. In any case i have no first hand experience and see no obvious advantages. As for rectification, didn't like them much.
yes it seems that they haven't changed much .....shame
they did look like they could be the next big thing back then .
I just thought I'd ask as I had seen bits on the internet but not enough to see how they would work any better .
so its back to the search for the ultimate IR type or what ever . thanks!
they did look like they could be the next big thing back then .
I just thought I'd ask as I had seen bits on the internet but not enough to see how they would work any better .
so its back to the search for the ultimate IR type or what ever . thanks!
pointy said:
Maybe nobody's replying because this has been discussed ad nauseam on this forum and it is also spelled out in Morgan Jones' book, so you're obviously not looking very hard if at all. The answer is cheap red LED's are best, both for cathode bias and CCS's, and if they don't get you the bias voltage you need, you can move to different colours or stack small signal diodes.
Within type, it's actually rather consistent. That's why I'll carry a battery, resistor, and voltmeter with me when rooting though surplus bins. If one LED is (say) 1.9V, all the others in the bin will be within 20mV or so of that value.
I suspect that the reason this is not done more commercially is pure inertia and marketing. The first I saw diode bias was in the late '70s. It never seemed to go anywhere. MJ made a very convincing case for me to try it again, and it's turned out to be such a good solution that I have trouble designing without it.
All the stuff about fast recovery and the like is totally irrelevant. Forward-biased AC impedance is the main parameter of concern. I've not seen any significant frequency dependence from LEDs below my measurement limit (100kHz).
I suspect that the reason this is not done more commercially is pure inertia and marketing. The first I saw diode bias was in the late '70s. It never seemed to go anywhere. MJ made a very convincing case for me to try it again, and it's turned out to be such a good solution that I have trouble designing without it.
All the stuff about fast recovery and the like is totally irrelevant. Forward-biased AC impedance is the main parameter of concern. I've not seen any significant frequency dependence from LEDs below my measurement limit (100kHz).
leadbelly said:
Guitar amps and pedals sometimes use diodes to clip off the top and bottom of the signal to achieve distortion. They are placed as shunts to ground. Sometimes they are LEDs which are purported to be "smoother" in that application. Many consider this approach sacrilegious in guitar amps whereas most would not say that regarding this approach in guitar pedals. This is because amps are “supposed” to get their distortion from overdriving the tube(s.) Using “diode clippers” is seen as “cheating.” I had a Marshall JCM 900 that used the diodes and I’m amongst those that don’t like the diode clipper approach in guitar amps. I converted the diodes to LEDs in the clipping section of my Boss DS-1 distortion pedal and confirmed that the LEDs clipped less of the signal since the amplitude of it’s output went up at the same settings. Still don’t use the pedal though.
I don't know if diodes are used in guitar amps in place of cathode resistors. I have not seen it that I remember.
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