WEBVTT

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See the diagram of the course: the switching MOSFET

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The pushbutton controls the gate via the 60 μA gauge ammeter

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No intensity (gate capacity is instantly charged)!

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Point of self-hold, simply the gate capacity remains charged

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Demonstration of the voltage control: + available on the ammeter

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In the right hand: the gate, left I touch the -: I extinguish

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Touching +: Full ignition

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I re-extinguished with the - and free gate, the lamp remains off

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Never leave the gate free "in the air"!

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In yellow on the left, voltage in gate. Right in red, voltage in lamp

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We want to measure gate voltages at the beginning and end of conduction!

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Reminder: on the left the gate, on the right the bulb

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Nothing under 1.1 Volt between gate and source

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Around 3.7 Volt between gate and source: start of conduction!

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It is only the very beginning: very low intensity, voltage in low lamp

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With 4.2 Volts, the conduction is close to the maximum

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Above approx. 7 Volts gate / source, no lamp change

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By shunting the transistor, I check the drop between drain and source # 0.04 Volt under 1.8 A

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This gives an RdsON of about 0.02 Ohm (0.04 / 2 A) against a maximum of 0.044 in datasheet

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The MOSFET is correct. We will check the end of conduction

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7.5 Flights: always the same RdsON

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It is only under 4.7 volts that the resistance Rds increases substantially

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Note the remarkable stability in resistive linear operation!

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Nothing to do with the bipolar is much lower

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Bb: the ability to gate. To accelerate switching, they are not controlled in 0/7 V

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But we pilot the gate in +10 Volts for conduction, and in -10 Volts for opening

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Thus, the expense transitions in joules losses are reduced. +/- 20 Flights = destruction

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Test: between drain and source: continuity tester

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Between gate and source: a battery 9 Volts, I feed: continuity

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To empty the gate / source capacity: connect the 2 or the connections to - 9 Volts