IRLZ44N model with parasitic capacitance and inductance driven by totem pole driver.

301

03:30:02

In this circuit we have a model of a practical MOSFET showing its parasitic capacitance and inductance. The MOSFET I am trying to model is the IRLZ44N. The n-channel MOSFET is being driven with a totem pole gate driver circuit. Although a 5V TTL signal would be sufficient I am using two NPN transistors to boost the TTL signal to 10V to feed the TOTEM pole. 

published 7 years ago

hurz

7 years ago

The push pull stage can not go over 5 minus Vbe which is ok for irlz44 but the 10V would be better to drive it secure into Rdson low. The capacitances around are not according spec. Ciss is 3.3nF cout=1.2nF and Crev= 200pF. The Vgsth you set to worse case 2V which is fine, cuz many rubbish from ebay is low perfomance electronics we get cheap. The model I would set for Rdson a little different to reach Rdson, but more or less its fine for what EC can do with it. The lambda value is much to high, but it doesn't have here in your application no effect.

hurz

7 years ago

Now its with double open collector inverter to keep logic and the push pull stage does get 10V and also the mosfet. But, is this the way you.communucate? I play radio comment while you change the circuit?

thestafman

7 years ago

Hi Hurz. Thanks for your comments. I added extra capacitance to make for parasitics. I am using supply voltage not only to reduce rds but also to reduce rise time as well. It is working perfectly on my perfboard at 30khz with 200mA load

hurz

7 years ago

Right, max 30kHz. The first transistors are not optimal driven with 1kOhm pullup they cause saturation which makes them slow. You pump 10mA into the base. For the push pull stage 2k is probably ok. But the stage before are just there to correct the logic. Do it in SW to turn the logic and try to build this with only one BJT open collector against 10V. It will be much faster. But as you can see on your perfboard already 333kHz as here in simulation is a little unrealistic for a real implementaion 😜 At least this simple.

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