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Recent content by D.A.(Tony)Stewart

  1. D.A.(Tony)Stewart

    Op amp as comparator - can't figure this out

    I think this is a process failure of unstated goals, design specs and assumptions. Even the signal source was not communicated for your source, Vin. You have an integrating differential amplifier and expecting some output transition. The actual gain is 1+ the integral of the input Vref ,so if...
  2. D.A.(Tony)Stewart

    Have trouble with biasing Cree transistor

    What values of ESL did you use in your simulator 0.8 nH/mm more or less? Any mutual coupling or crosstalk from source to gate. What was the actual impedance of the gate current sensor? What value did you use for parasitic capacitance ? You have to perfect your understanding at lower...
  3. D.A.(Tony)Stewart

    Have trouble with biasing Cree transistor

    With positive feedback at unity gain , the 1st resonance to engage when gm rises will accelerate rapidly into amplifying Vgs into saturated oscillation. To avoid this, revisit the Barkhausen Criteria, avoid ESL where this margin is lost in Vgs and establish a stable voltage source for your DC...
  4. D.A.(Tony)Stewart

    Using IGBT or Mosfet

    Correction: #26 link was Tosbiba' not AD https://toshiba.semicon-storage.com/eu/semiconductor/knowledge/faq/mosfet_igbt/igbt-002.html 1714170534 Hi Sabu, You ought to know that you cannot choose an optimal design without details on dynamic and reactive load impedance ( time and frequency)...
  5. D.A.(Tony)Stewart

    Using IGBT or Mosfet

    The AD's datasheet plot below indicates for almost same Imax rating in Si MOS vs IGBT, shown for static loads. IGBT's are the same as FET when using 50% or rated current then IGBT's have lower loss from lower Rce than RdsOn in spite of 0.7V diode offset. This crossover threshold drops as the...
  6. D.A.(Tony)Stewart

    Using IGBT or Mosfet

    It seems everyone is computing power incorrectly and not including dynamic power loss. For Miller Capacitance I recall the dynamic peak will escalate rapidly above static loss at if the date drive resistance is not low enough <= Rg input. Then the dynamic FET loss Pavg increases with f but does...
  7. D.A.(Tony)Stewart

    How to implement mosfet with large width

    Along with ultra-low RdsOn and Vgs is high Cout, Cin, Cdg and stability concerns with low ESR C load ranges. I wonder what the limitations are for partial discharge in the gap at max V or fabrication challenges?
  8. D.A.(Tony)Stewart

    Using IGBT or Mosfet

    Ron = 0 is never ideal, unless your reactance parts are so lossy that they provide the necessary damping factor or Q at minimum load. Thus, you need to define your max/min load ratio or discrete values with time and determine your loop stability margin in each state for a step load in either...
  9. D.A.(Tony)Stewart

    How to implement mosfet with large width

    Which assumption or calculation is most likely in error?
  10. D.A.(Tony)Stewart

    Internal RC oscillator for reliable USART

    This is how UARTs work. Sync bit on Start edge, confirm at midbit, then stored every bit x clocks later where x= is normally 16. So since you have at least 10 bits per word, the worst case is 10% freq error or +/-5% f. Synchronous streaming data without start or stop bits uses a PLL to lock...
  11. D.A.(Tony)Stewart

    Internal RC oscillator for reliable USART

    To prevent a timing error the stop bit state must occur within 10% of the time for 1b start + 8b + 1b stop = 10 bits, all of the time for 10^n bits. The total stackup error includes; the oversampling clock resolution. Usually 1/16 b for a 16x clk. the Tx % error in f the Rx % error in f the...
  12. D.A.(Tony)Stewart

    PTAT current source vs LDO to bias a ring oscillator for PVT insensitivity and power

    There is a varicap effect on reverse bias PN junctions that reduces Cavg with Vdd so lowering the supply might offset the RdsOn which moves in the opposite direction of Cavg for Gate , Drain or Miller capacitance. I would expect series Rs and shunt Cavg to be the main factors of a ring...
  13. D.A.(Tony)Stewart

    Vintage potentiometer repair: What compound to use?

    Fine-grained plaster might shrink and detach more than tile grout. Moisture content must be low to survive and that might be a challenge. You do it trial and error but it all depends how many watts are dumped into these wires and the junction temp. Contact resistance and top surface flatness...
  14. D.A.(Tony)Stewart

    connecting two resonators in series

    Yes Volker, "will melt" meaning future tense. I would expect the stripline to look more robust to handle this power. Wouldn't you? I might expect 5mm w. over 2.5mm h. of Kapton or alumina or more.

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