+ Reply to Thread
Results 1 to 7 of 7

Thread: imulate a small Voltage Drop Out with MOSFET vs. parasitic capacitances

  1. 21st December 2006 09:57 AM #1
    dirkdiggler2oo2
    dirkdiggler2oo2 is offline
    dirkdiggler2oo2 Newbie
    Join Date
    Dec 2006
    Posts
    3

    Question imulate a small Voltage Drop Out with MOSFET vs. parasitic capacitances

    Hello,

    i want to simulate a small voltage drop out (variable between 1us to 40us), the supply voltage is also variable (between +5V to +35V).

    On the basis of the facts that a relay is to slow i think about a MOSFET, it should withstand high voltage and high current.

    The problem i have is that to switch in MHz-range i need high current so that the MOSFET parasitic capacitances are reloaded and the waveform of switching have a rectangle signale form.

    Does anybody know a solution to eliminate parasitic capacitances ?
    Reply With Quote Reply With Quote  

  2. 21st December 2006 10:38 AM #2
    Analog
    Analog is offline
    Analog Okay
    Join Date
    Jul 2006
    Location
    Michigan USA
    Posts
    476

    Default

    I don't think the MOSFET would be the problem, many MOSFETs can switch in the MHz range (you didn't specify what frequency). The problem is what it is driving. The capacitance on the drive side will drastically effect the signal, because as we all know, you can't instantaneously change the voltage on a capacitor. What are you driving? What are its characteristic capacitance and inductance values???
    "Everything that is done in the world is done by hope." -Martin Luther
    "There are two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle."-Albert Einstein
    Reply With Quote Reply With Quote  
  3. 21st December 2006 11:23 AM #3
    dirkdiggler2oo2
    dirkdiggler2oo2 is offline
    dirkdiggler2oo2 Newbie
    Join Date
    Dec 2006
    Posts
    3

    Default

    my switching frequency is between 25kHz (1/40us) up to 1MHz (1/1us).

    I want to drive a pump, motor applikation so i have to provide min. 2A, but i don't know the capacitance and inductance valuesat time
    Reply With Quote Reply With Quote  
  4. 21st December 2006 02:17 PM #4
    Hero999
    Hero999 is offline
    Hero999 Excellent Hero999 Excellent Hero999 Excellent Hero999 Excellent Hero999 Excellent Hero999 Excellent Hero999 Excellent Hero999 Excellent Hero999 Excellent Hero999 Excellent
    Join Date
    Apr 2006
    Location
    England
    Posts
    13,076

    Default

    Why do you want to do that?

    Are you talking about PWM? Normally a lower frequency is used for that.

    I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

    Please ask on the open forum if you have a question and I'll be happy to help,     if I know the answer.
    Reply With Quote Reply With Quote  
  5. 22nd December 2006 09:42 AM #5
    dirkdiggler2oo2
    dirkdiggler2oo2 is offline
    dirkdiggler2oo2 Newbie
    Join Date
    Dec 2006
    Posts
    3

    Default

    no pwm, i want to simulate a short break down of the power supply voltage
    Reply With Quote Reply With Quote  
  6. 22nd December 2006 11:58 AM #6
    Analog
    Analog is offline
    Analog Okay
    Join Date
    Jul 2006
    Location
    Michigan USA
    Posts
    476

    Default

    Quote Originally Posted by dirkdiggler2oo2
    no pwm, i want to simulate a short break down of the power supply voltage
    It is unlikely that a power supply would drop out with a sharp drop like that. The filtering caps in a supply would prevent that from happening. Can you elaborate on what type of fault would drop the supply like that?
    "Everything that is done in the world is done by hope." -Martin Luther
    "There are two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle."-Albert Einstein
    Reply With Quote Reply With Quote  
  7. 22nd December 2006 02:30 PM #7
    Sceadwian
    Sceadwian is offline
    Sceadwian Excellent Sceadwian Excellent Sceadwian Excellent Sceadwian Excellent Sceadwian Excellent Sceadwian Excellent Sceadwian Excellent
    Join Date
    Oct 2006
    Location
    Rochester, NY U.S.
    Posts
    9,825
    Blog Entries
    1
    Send a message via AIM to Sceadwian Send a message via Yahoo to Sceadwian

    Default

    A fault on the circuit side, or wireing fault coming from the power supply. Just off the top of my head (not the original poster)
    "Because I be what I be. I would tell you what you want to know if I
    could, mum, but I be a cat, and no cat anywhere ever gave anyone a
    straight answer, har har."
    Reply With Quote Reply With Quote  
+ Reply to Thread
« Previous Thread | GPS to Serial connector »

Similar Threads

  1. Resistors
    By Marks256 in forum General Electronics Chat
    Replies: 57
    Latest: 16th May 2009, 10:22 PM
  2. Analog Meter
    By windozeuser in forum General Electronics Chat
    Replies: 19
    Latest: 3rd October 2007, 02:44 PM
  3. Motor current sensing
    By ptewright in forum Electronic Projects Design/Ideas/Reviews
    Replies: 11
    Latest: 19th May 2006, 12:29 AM
  4. I am not getting ripple voltage at the output
    By dar2525 in forum General Electronics Chat
    Replies: 3
    Latest: 14th July 2005, 02:21 PM
  5. Reducing Voltage for small motor control
    By DirtyLude in forum Electronic Projects Design/Ideas/Reviews
    Replies: 6
    Latest: 18th April 2004, 09:29 PM

Tags for this Thread