chandresha1
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I am working on H-bridge circuit with PWM. It is basically class-D amplifier with four N-channel Mosfet. However, i am stuck at one-point. How to calculate the drain current for high side Mosfet? The configuration is shown in figure.
I am applying 30V Gate voltage(Respect to Ground). Drain is connected to the positive power supply rail of 20V. Source is connected with load.
What i have understood is in such a configuration, when i apply the Gate voltage higher than Vds, Mosfet works in triode mode. In other words it will act as a switch with very small ON-resistance of Rds(on). Because of this, the potential difference between drain and source becomes almost zero or around 200-300 mV.(Vs = Vd-id*Rds(ON).) At this point i am getting confused. According to Mosfet characteristic curve, for Vds=0, the drain current is zero. Than how can we say mosfet acts as a switch? Because according to curve, Mosfet will conduct very small current.
![edaboard.png edaboard.png](https://www.edaboard.com/data/attachments/55/55892-6b314693555fee63056004d29aa80a94.jpg)
![Mos_Mode.png Mos_Mode.png](https://www.edaboard.com/data/attachments/55/55893-0b6f5c89d7cb02692958845312a463fb.jpg)
I am applying 30V Gate voltage(Respect to Ground). Drain is connected to the positive power supply rail of 20V. Source is connected with load.
What i have understood is in such a configuration, when i apply the Gate voltage higher than Vds, Mosfet works in triode mode. In other words it will act as a switch with very small ON-resistance of Rds(on). Because of this, the potential difference between drain and source becomes almost zero or around 200-300 mV.(Vs = Vd-id*Rds(ON).) At this point i am getting confused. According to Mosfet characteristic curve, for Vds=0, the drain current is zero. Than how can we say mosfet acts as a switch? Because according to curve, Mosfet will conduct very small current.
![edaboard.png edaboard.png](https://www.edaboard.com/data/attachments/55/55892-6b314693555fee63056004d29aa80a94.jpg)
![Mos_Mode.png Mos_Mode.png](https://www.edaboard.com/data/attachments/55/55893-0b6f5c89d7cb02692958845312a463fb.jpg)