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Deloca

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Designer/Educator

Electronics hobbyist, engineer, physicist. I have lived and worked in quite a few places around the world. Overall, I believe in a united, peaceful and caring humanity since we have one home that connects all of us. Planet Earth.


Deloca

's contributions
  • 08.11.2014
  • Hybrid vacuum tube/solid-state audio power amplifier
  • There is a school of thought that says amplifiers with vacuum tube front-ends sound markedly different, even mellow - the a benefit of the enhanced thermionic emission. The author implies it also "with very crisp, tightly controlled bass and a natural midrange...". I imagine that kind of sound appeals to many but is hard to replicate solely with transistors.
  • 08.04.2014
  • HB-LED flashing beacon repurposes switching regulator
  • It is not clear exactly how C1 discharges, i.e. through what impedance. The charging of C1 occurs through a constant current source of about 330mA, but for the sake of finding the approximate frequency expression it would be nice to talk a bit more about the discharge mechanism. And referring one to the datasheet of the 34063 isn't cool either. Otherwise an interesting circuit.
  • 07.21.2014
  • Improve efficiency of low-cost switcher
  • That's a neat method to reduce the power dissipation in Q2 that leads to higher output efficiency. What are the considerations for selecting C1 for the general PWM driver that can, for instance, work at several MHz? I think the 34063 works at 100kHz tops.
  • 07.14.2014
  • Variable HV power supply employs photovoltaic optocoupler
  • Nice concept, I have seen such a scheme used for a 48V telecoms line. It would have been really neat to power the converter offline and derive and auxiliary supply for the controller from there as well and eliminate the separate 15V.
  • 06.05.2014
  • SPICE models need correlation to measurements
  • I use Spice (mostly LT-Spice but other variants as well) on a daily basis and I concur with many of your observations and conclusions. In particular that uncorrelated models are necessarily "dangerous assumption". What compounds the danger is the underlying and almost de-facto "trust factor" owing to the association of the model with its OEM source. At one point, during a simulation of the TL431 programmable zener diode, I found that the device became unstable under certain conditions, in spite of what the datasheet claimed. Luckily, though, I was able to harness the oscillation and presented in a DI a possible application: VCO using the TL431 reference.
  • 05.31.2014
  • Three-transistor current source covers wide range
  • WINFIELD.HILL those are my observations exactly. In fact I had simulated the circuit in LT-Spice and the simulation outputs supports adding an emitter resistor to Q2. I added a temperature dependence to the models of either Q1 or Q2 independently and the circuit performs more resiliently. I used visible LED models in LT-Spice and the circuit still operates similarly but with VD1 around 2.4V; By the way, are you the same Winfield Hill who co-authored "The Art of Electronics" with Paul Horowitz? That book has been my bible from my early teenage years. I keep a copy wherever I go. Many regards, D