I'm working on an RGB LED project for which I have designed a driver (Original Design). Everything seems to be in place but there is some problem that is causing the Drains/Output to be always High even though I've not connected the Gates of transistors with any input source. I'm planning to use it on arduino and PWM signals to be fed in from the Digital Pins.

The Transistors (Q1, Q2, Q3) are IRF540N and Resistance (R1, R2, R3) are 22K Ohms. Ground of driver will be connected to Ground of arduino and +ve of Power source (J2). Please suggest if there is an issue in the schematic below.

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  • \$\begingroup\$ The original schematic states that 10k needs to be used, have you tried that ? \$\endgroup\$ – Triak Dec 6 '15 at 9:39
  • \$\begingroup\$ Do some measurements around the fet. \$\endgroup\$ – PlasmaHH Dec 6 '15 at 9:53
  • \$\begingroup\$ As it currently stands, they should all be high because the MOSFETs are turned off. \$\endgroup\$ – Andy aka Dec 6 '15 at 10:52
  • \$\begingroup\$ @Andyaka, yes you are correct. They all are high, but as the Gates are at Low, why should these be high. Can you please explain? \$\endgroup\$ – DigitalEther Dec 6 '15 at 12:52

They all are high, but as the Gates are at Low, why should these be high

The MOSFETs are open circuit and even with the lightest load between drain and positive power rail, the drains will tend to float up to that rail.

  • \$\begingroup\$ What is it that you don't understand about my answer @DigitalEther ? \$\endgroup\$ – Andy aka Nov 29 '20 at 15:05

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