For my continuing education, can anyone tell me why the voltage regulator in the picture doesn't blow the mosfet gate when the zeners value exceeds 20 volts.
Also, are there conditions where the mosfet gate is allowed to exceed 20 volts in an amplifier circuit?
Also, are there conditions where the mosfet gate is allowed to exceed 20 volts in an amplifier circuit?
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When the voltage is more than 20 volts across gate and source you will blow the mosfet but now the voltage is only 3-4 volts. A good way of learning is to use LTSpice which is free to download.
The gate must always stay under 20 volts because excessive voltage is distructable. The mosfet will die if you apply gate voltages around 25-30 volts. I have tested this myself.
The gate must always stay under 20 volts because excessive voltage is distructable. The mosfet will die if you apply gate voltages around 25-30 volts. I have tested this myself.
The voltage at GATE can be 100 Volt or more .. even 1.000 Volt
as long as the voltage at source is not too low.
In your circuit, if the voltage at GATE is 40 V
then at the SOURCE will be at something like 36 V. Only 4 Volts lower.
And those remaining 36 Volts will be across the load.
The absolute Voltage related to GROUND, is something the MOSFET never can see.
MOSFET will see the difference between Gate-Source,
and in most cases Vgs is like 3-6 V in a normal circuit.
as long as the voltage at source is not too low.
In your circuit, if the voltage at GATE is 40 V
then at the SOURCE will be at something like 36 V. Only 4 Volts lower.
And those remaining 36 Volts will be across the load.
The absolute Voltage related to GROUND, is something the MOSFET never can see.
MOSFET will see the difference between Gate-Source,
and in most cases Vgs is like 3-6 V in a normal circuit.
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