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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

    The revised and improved circuit WILL NOT WORK with TL080 opamps because their inputs do not work when their voltage is close to the negative supply. Also their maximum allowed supply voltage is too low so they will not be reliable and might fail immediately. Also a TL080 opamp needs a...
  2. audioguru2

    0-30 Vdc Stabilized Power Supply

    I do not know which schematic you have. Mine is crystal clear when you click on its address to make it fill your screen:
  3. audioguru2

    0-30V Stabilized Power Supply

    It will be fine if it has a load of at least 5mA and an input from 19V to 35V.
  4. audioguru2

    0-30 Vdc Stabilized Power Supply

    R2 and C2 couple the AC from the transformer to D5 and D6 so these rectifiers can make the -1.3V negative supply. Sometimes the output of opamp U3 needs to be -0.7V so U3 uses the negative supply.
  5. audioguru2

    0-30V Stabilized Power Supply

    A single 11.2V zener diode powered from a resistor has much worse voltage regulation than a 5.6V one and the 5.6V one is powered by a constant current opamp circuit that makes it even better.
  6. audioguru2

    0-30 Vdc Stabilized Power Supply

    1) The datasheet for the BD139 shows that its maximum Operating and Storage Junction Temperature is 150 degrees C which is the maximum allowed internal temperature of its chip. 2) Its Thermal Resistance Junction to Ambient is 100 degrees C which is the chip's temperature rise when the transistor...
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    I do not understand. I showed that in this circuit its maximum dissipation is 2.7W, not 1.5W. In its datasheet it is spec'd to be able to dissipate 8W with a heatsink that cools its mounting base to 70 degrees C and shows that its thermal resistance is 10 degrees C per Watt then a suitable small...
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    Are you making the latest improved circuit that has a 28V-30V transformer, TLE2141 opamps, a BD139 driver transistor and two 2N3055 output transistors? Did you calculate the maximum amount of heat the BD139 will produce? 1) The minimum hFE of each 2N3055 transistor at 1.5A is about 43 so both...
  9. audioguru2

    0-30 Vdc Stabilized Power Supply

    The transition frequency for the STN851 transistor is 130MHz, it is 190MHz for the BD139 and it is 250MHz for the original 2N2219 transistor. The STN851 will work fine.
  10. audioguru2

    0-30 Vdc Stabilized Power Supply

    The BD139 is a fast driver transistor. The 2N5886 that you want to use is a slow power transistor. The driver transistor needs to be fast to avoid overshoots or oscillation when the output current changes abruptly.
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    I hope that the surface-mount TL2141 does not exceed its maximum allowed temperature when the ambient temperature is high, the output current is high, the voltage is set low or a shorted output, the quiescent current of the TLE2141 is high and the hFE of the driver and output transistors are low.
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Redwire, Will the tiny surface-mount TL2141 for location U2 survive the heat?
  13. audioguru2

    Having problems with chip and DC motor and potentiometer and Arduino....

    On the other website forum you said you accidently applied 11V instead of 5V to this circuit which fried the Arduino. Then the circuit worked fine when the 5V was 5V and the burnt Arduino was replaced.
  14. audioguru2

    Having problems with chip and DC motor and potentiometer and Arduino....

    I see no schematic, just a bunch of wires and parts on a breadboard. There is no text and no instructions. The pot will control the speed of the motor with PWM if the Arduino makes PWM pulses.
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    Here are the latest schematic and parts list again:
  16. audioguru2

    0-30V Stabilized Power Supply

    The voltage regulation is good at any amount of gain. A gain of 2.7 is used because the reference zener diode D8 is 5.6V which has the best regulation and opamp U1 is a current source for it that doubles the reference voltage to 11.2V. Then for a maximum output of 30V a gain of 30V/11.2V= 2.6786...
  17. audioguru2

    0-30V Stabilized Power Supply

    No. The load regulation is excellent. The line regulation is also excellent. The very high open-loop voltage gain of the opamp driving the driver and output transistors allow the negative feedback from R11 and R12 to keep the output voltage at almost the same voltage as at the voltage-setting...
  18. audioguru2

    0-30V Stabilized Power Supply

    What are you talking about, Kevin? With an output current of 3A from the project, the driver transistor is an emitter-follower with a voltage gain of 0.9. The two output transistors have a voltage gain of about 0.85 which is reduced to 0.8 by their emitter resistors. Then their total voltage...
  19. audioguru2

    0-30V Stabilized Power Supply

    No. This is my improved design. It works very well. Recently we found out that the MC34071 opamps are no longer available in through-hole packages so the Texas Instruments TLE2141 opamps should be used instead.
  20. audioguru2

    Yamaha am/fm tuner model T-33

    We speak English here. What language are you using and who do you think will answer you?
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