Please have a look at my below circuits.
The first one is an MOSFET. N-MOS.
Gate is fed with a function generator input of 5V peak to peak. 1kHz frequency. 1ms period. 90% duty cycle. Drain is provided with 10V and the source is connected to a load resistor.
If I probe at the gate and the source, I get the below waveform :
Please consider only the yellow and blue trace in the above waveform. Yellow is probed at the gate. Blue is probed at the source of the MOSFET.
If I connect the MOSFET to the circuit shown above, i.e., my second circuit, the same FG input is provided to the GATE of the MOSFET.
Now, I probe at the point A and the Gate of the MOSFET. Below is the waveform :
Yellow is the GATE of the MOSFET. While blue is probed at Node A.
My questions are :
- In the second waveform and the second circuit, shouldn't the voltage at node A, follow the voltage at the GATE of the MOSFET? The node A voltage should also go to 0V while the Gate voltage goes to 0V. Why am I not getting that 0V waveform at the Node A?
- What effect does the resistor connected to the source of the MOSFET and the purpose of the C1 50nF capacitor in this circuit.