A properly designed driver using discrete components would of course work good. However, when driving a larger gate charge, a specialized MOS driver would ensure that the MOSFET gets fully switched ON. Do also take note that the IRF740 has a higher gate charge than other lower current, voltage mosfet. Tan Chun Chiek ----- Original Message ----- From: "Kevin Howell" To: Sent: Sunday, April 14, 2002 1:26 PM Subject: Re: [EE]:High power DC switching.. > Does that mean I won't get away with a 2N2222 or a opto-isolator between the > PIC and the MOSFET? > > > -----Original Message----- > From: pic microcontroller discussion list > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Code > Sent: 14 April 2002 06:50 AM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [EE]:High power DC switching.. > > > you'll need a MOS driver that's capable of driving large capacitive load > > http://www.national.com/pf/DS/DS0026.html > > > ----- Original Message ----- > From: "Kevin Howell" > To: > Sent: Sunday, April 14, 2002 5:13 AM > Subject: Re: [EE]:High power DC switching.. > > > > Thanks I found the datasheet on the IRF740, I didn't know that there are > > inherent problems when driving a MOSFET (Cgs) . Now the search is on for a > > mosfet driver. Can't the IRF740 b interfaced directly to a PIC? Surely it > > was designed with a microcontroller in mind? > > > > Thanks > > Kevin > > > > -----Original Message----- > > From: pic microcontroller discussion list > > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of PY2NI > > Sent: 13 April 2002 10:22 PM > > To: PICLIST@MITVMA.MIT.EDU > > Subject: Re: [EE]:High power DC switching.. > > > > > > As a starting device try 2 or more IRF 740 (400V @ 10A each) you have > > better options if you don't put more than 200V on the FET you can use only > 2 > > IRF 640 (200V @ 18A each). MOSFets are really friendly devices when you > pay > > attention on how to handle then, especial care with driver circuits, some > of > > then have quite a large input capacitive reatance. Cgs. There are > especial > > ICs (GATE DRIVERS) designed to deal with this problem if you don't want to > > waste your time doing this. > > Hope it helps a bit. > > > > P.S. the devices mentioned aren't expensive, I often buy then for a buck > or > > less. > > > > [ ] s > > Horta > > > > > > ----- Original Message ----- > > From: Kevin Howell > > To: > > Sent: Saturday, April 13, 2002 3:26 PM > > Subject: Re: [EE]:High power DC switching.. > > > > > > > I can't find any Mosfets that can handle 200-300V. The problem is not to > > > source them but to find a suitable part. (Keep in mind the 20A) > > > > > > Thanks > > > Kevin > > > > > > > > > -----Original Message----- > > > From: pic microcontroller discussion list > > > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Bob Blick > > > Sent: 13 April 2002 06:44 PM > > > To: PICLIST@MITVMA.MIT.EDU > > > Subject: Re: [EE]:High power DC switching.. > > > > > > > > > > I have some high power fast switching transistors, BUV48, which I want > > to > > > > use to control a 220V DC motor using PWM. The transistor can handle > 10A > > Ic > > > > and 400 Vce (hfe =8!!). My problem is that the motor draws up to 20A > and > > > > thus I will > > > > need more than one of these transistors in possibly a darlington > > > > configuration. Please can someone help me with a circuit to control > this > > > > current hungry motor using a pic ... > > > > > > Hi Kevin, > > > > > > Do you really have to use this transistor? Do you already have some > > > other transistors to use as drivers for them? If not, perhaps you > > > should consider some other transistors, I would suggest MOSFETs. > > > Your losses will generally be lower. Also if you do PWM you will > > > need a freewheel diode across the motor. > > > > > > Others will likely also have suggestions. A transistor with hfe of 8 > > > doesn't sound like a whole lot of fun. > > > > > > Cheers, > > > > > > Bob > > > > > > -- > > > http://www.piclist.com hint: The list server can filter out subtopics > > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > -- > > > http://www.piclist.com hint: The list server can filter out subtopics > > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > > > > > > > -- > > http://www.piclist.com hint: The list server can filter out subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > -- > > http://www.piclist.com hint: The list server can filter out subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.