# mosfet chanel p

#### the kid

Joined Jan 4, 2015
81
Hello everyone
Now i m working with a p chanel mosfet irf9540. I need a driver circuit for the mosfet to operate at high speed. Please help me!
Thank for attention

#### Bordodynov

Joined May 20, 2015
3,188
What is the supply voltage.
The input voltage level of the control pulses.
How fast should be the driver.

#### Picbuster

Joined Dec 2, 2013
1,049
No answer without the Gate freq given. the input cap = 1300pf approx. you must be able to charge and discharge this cap. The energy needed to do so is related to the freq.

#### Bordodynov

Joined May 20, 2015
3,188
Answer my questions and I'll give a recommendation on the application of the finished driver or draw you a diagram of discrete components. Performance is a relative concept. For some, it is enough to 100 nsec, in whom the 10 nsec much.
Tell me what you are going to generate a control signal. It is important that you switch. And it is very important to voltage how you connect to the source of the transistor.

#### the kid

Joined Jan 4, 2015
81
Answer my questions and I'll give a recommendation on the application of the finished driver or draw you a diagram of discrete components. Performance is a relative concept. For some, it is enough to 100 nsec, in whom the 10 nsec much.
Tell me what you are going to generate a control signal. It is important that you switch. And it is very important to voltage how you connect to the source of the transistor.
I want to drive p chanel mosfet for buck converter. My dc_dc convert operate at 25 khz. Input voltage is 40vdc. I need a driving circuit for that mosfet.

#### Bordodynov

Joined May 20, 2015
3,188
See

#### crutschow

Joined Mar 14, 2008
34,855
D2 and D3 are not needed to protect the MOSFET gate since the ratio of R1 and R3 will generate a maximum Vgs at the MOSFET of about -11V.

I got better gate rise and fall times in my simulation by using BC337-40 for the NPNs and a BC807-40 for the PNP.

#### the kid

Joined Jan 4, 2015
81
Thank u very much, can you explain principle of this circuit

#### Bordodynov

Joined May 20, 2015
3,188
D2 and D3 are not needed to protect the MOSFET gate since the ratio of R1 and R3 will generate a maximum Vgs at the MOSFET of about -11V.
I got better gate rise and fall times in my simulation by using BC337-40 for the NPNs and a BC807-40 for the PNP.
I agree with you about the NPN transistor. Replacing the PNP transistor is not suitable. The simulation showed that, without the limiter gate-source voltage up to 14 volts. Limiter makes this scheme more reliable. For example the scheme is not critical to the values of resistors.

Thank u very much, can you explain principle of this circuit
This system is designed for the control of the microcontroller of the transistor. It simulates the gate. Power supply 5 volts. lower transistor current generator is deactivated. The current is switched on and off by the controller. Current=(5V-0.7V)/R3.
In this case, no current goes through the resistor R1. anything goes and then the MOS transistor opens. Sufficient charging and discharging current provided Q1 and Q2.

#### the kid

Joined Jan 4, 2015
81
Can
I agree with you about the NPN transistor. Replacing the PNP transistor is not suitable. The simulation showed that, without the limiter gate-source voltage up to 14 volts. Limiter makes this scheme more reliable. For example the scheme is not critical to the values of resistors.

This system is designed for the control of the microcontroller of the transistor. It simulates the gate. Power supply 5 volts. lower transistor current generator is deactivated. The current is switched on and off by the controller. Current=(5V-0.7V)/R3.
In this case, no current goes through the resistor R1. anything goes and then the MOS transistor opens. Sufficient charging and discharging current provided Q1 and Q2.
I have not understood that ideal.
Could you represent turn on and turn off operation of the mosfet in detail. Please

#### Bordodynov

Joined May 20, 2015
3,188
See. I advise you to install and use, free program LTspice.

#### crutschow

Joined Mar 14, 2008
34,855
I agree with you about the NPN transistor. Replacing the PNP transistor is not suitable. The simulation showed that, without the limiter gate-source voltage up to 14 volts. Limiter makes this scheme more reliable. For example the scheme is not critical to the values of resistors.
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Why is replacing the PNP "not suitable"?
Yes, using the diodes makes the circuit insensitive to resistor values but, for a fixed set of the proper value resistors and a given supply voltage, they aren't needed.
A Vgs of -14V is well within the MOSFET rating of 20V, but if you want to reduce it, just increase the value of R3 to the appropriate value. For example, 430Ω should give a Vgs of about -10V.

#### Bordodynov

Joined May 20, 2015
3,188
I want the gate voltage of the transistor was about 10-12V. The result was the release of up to 14V. Power supply has spread (if it is after the rectifier transformer). Resistors are also spread as 5V. Efficiency of the converter is more dependent on off. For frequency 25kHz 100ns are more than enough. Sorry for my English. I now use the phone.

#### the kid

Joined Jan 4, 2015
81
Why is replacing the PNP "not suitable"?
Yes, using the diodes makes the circuit insensitive to resistor values but, for a fixed set of the proper value resistors and a given supply voltage, they aren't needed.
A Vgs of -14V is well within the MOSFET rating of 20V, but if you want to reduce it, just increase the value of R3 to the appropriate value. For example, 430Ω should give a Vgs of about -10V.
how to replace PNP transistor. can u explain about that?
Could you make me to understand about role of Q1 and Q2 transistors. please

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#### the kid

Joined Jan 4, 2015
81
thank all

#### crutschow

Joined Mar 14, 2008
34,855
how to replace PNP transistor. can u explain about that?
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I meant replace it with a different part number.