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  1. Alec_t

    4049 hex inverting ic

    Welcome to EP! Ground 7 and 9. Leave 6 and 10 unconnected. Unused inputs of CMOS circuits should never be left floating.
  2. Alec_t

    Oscillations in the gate signal with IXFN 150N65X2 transistors

    There is a bunch of components between the HCPL3120 and the FET gate. I haven't tried to work out what purpose it all serves, but it inevitably introduces parasitic capacitance and trace inductance which could cause ringing or pick up EMI.
  3. Alec_t

    LED Light Fading Problem

    I'd also check to see if the values of any series resistors have gone high, or their connections have developed dry joints.
  4. Alec_t

    electronic load

    No. It won't do the same because there is virtually no voltage drop across the (series) gate resistor except when Vgs is actually changing and the gate capacitance is being charged/discharged. The FET gate is insulated. This is unlike a BJT where current flows through the base-emitter junction...
  5. Alec_t

    electronic load

    Fine in theory, difficult in practice when the FETs aren't fully on or off. Because of production spreads, even FETs from the same batch are unlikely to have exactly the same Vgs/drain-current characteristic. The result is that they won't share current equally and will probably self-destruct...
  6. Alec_t

    electronic load

    No. How did you arrive at that figure? Here's what the datasheet says: Absolute maximum power is 156W, provided you can keep the case temperature Tc down to 25C. If Tc is, say, 50C then the maximum power is derated to only 156-1.25*(50-25) = 125W. You also have to consider the junction...
  7. Alec_t

    electronic load

    Are you aware that the mounting tab of the FET is electrically connected to the FET drain (unless you have the T0-220F package version) ?
  8. Alec_t

    electronic load

    Even if the FET isn't oscillating, its sole purpose as an electronic load is to dissipate energy. Energy = current x voltage x time. Most of the voltage is dropped across the FET drain-source (55V at the drain, ~3V max at the source); a much smaller voltage (~3V max) is dropped across the shunt...
  9. Alec_t

    electronic load

    The FET takes the brunt of the heat dissipation; not the shunt.
  10. Alec_t

    electronic load

    0.15Ω would certainly reduce the heat in the shunt, but any FET is still going to roast at 260W!
  11. Alec_t

    electronic load

    Shouldn't be necessary if (1) the FET is a logic-level type and (2) the gate isn't being switched rapidly. A gate series resistor of, say, 330Ω would reduce the source current required from the opamp output. Can you use a lower resistance shunt? 0.6Ω would dissipate 15W at 5A.
  12. Alec_t

    electronic load

    Welcome to EP! An LM358 with a supply of 5V can provide a maximum output voltage of about 3.8V, so Vgs = 3.8V - 0.8V = 3V. 0.8V across 0.6Ω implies 1.33A current. At 1.33A current the minimum drain-source voltage Vds of the FET is about 2V, provided Vgs is at least 4.5V (according to Fig 2 of...
  13. Alec_t

    Analog Circuit to Randomly Modulate Amplitude and Frequency

    :confused: If it has to be replicable then how can the modulation be random?
  14. Alec_t

    EDLC and Li-ion hybrid supercapacitors - claims that don't add up.

    Sub/sup show ok in Firefox/ Win10.
  15. Alec_t

    Light bulbs as dummy load for Stereo ?

    An electric kettle element would run at a lower temperature than a bulb filament, so the hot/cold resistance variation would be less.
  16. Alec_t

    SuperCap Charging and Delivery System using Solar Panels

    Is this the sort of thing you're after?
  17. Alec_t

    Light bulbs as dummy load for Stereo ?

    .... but maybe < 50 Ohms when cold.
  18. Alec_t

    SuperCap Charging and Delivery System using Solar Panels

    Input = 3 x 1.25W = 3.75W. Output = 5V x 1A = 5W. Do you see a problem there?
  19. Alec_t

    Light bulbs as dummy load for Stereo ?

    If the bulb replaces the loudspeaker, i.e acts as a dummy load, then clearly the loudspeaker is protected :confused:. Did you mean use the bulb as a dummy load, or use the bulb in series with the speaker to limit current? Bear in mind that the bulb rating specifies wattage at the rated voltage...
  20. Alec_t

    Analog Circuit to Randomly Modulate Amplitude and Frequency

    What visual effect requires a sine-wave? It might be easier to come up with a solution if the wave-form isn't critical. Be aware that light flashes/pulses in the ~ 5Hz-10Hz range can trigger epileptic seizures in susceptible people.
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