Mosfet off resistance

Started by Juo in sci.electronics.design6 years ago 7 replies

I'm trying to use a mosfet as a switch in a low power application( < 100uA). The mosfet will turn off the device. With V_GS = 0V how well does...

I'm trying to use a mosfet as a switch in a low power application( < 100uA). The mosfet will turn off the device. With V_GS = 0V how well does the mosfet do this? The drain leakage in the data sheet says around 10uA. Does this mean that the mosfet will act like a 1M resistor for 10V Vcc? What I'm worried about is that my device my not turn off completely due to the leakage of the mosfet. Th


Problem applying a mosfet

Started by default in sci.electronics.design10 years ago 29 replies

I'm trying to use a logic level mosfet to switch on a camera. The camera is a 3 volt type designed for AAA batteries and works fine with NiMH...

I'm trying to use a logic level mosfet to switch on a camera. The camera is a 3 volt type designed for AAA batteries and works fine with NiMH down to about two volts and alkaline to about two volts. The mosfet drops about 20 millivolts when operating the camera, yet for some reason the supply has to be greater than 3.5 volts with the mosfet in the circuit. Mosfet is IRLZ24 type, N channe...


MOSFET Usage

Started by Ron M. in sci.electronics.design7 years ago 26 replies

I am in the process of designing a device that uses 30A MOSFET for the output. I need it to apply a 12 Vdc source to a switchable load on...

I am in the process of designing a device that uses 30A MOSFET for the output. I need it to apply a 12 Vdc source to a switchable load on the ground side. Are there any major issues using a MOSFET in this way?


"Jellybean" HV low power MOSFET

Started by Ralph Barone in sci.electronics.design3 years ago 8 replies

Can anybody suggest a cheap, easily obtainable > = 400 V, < 2A thru hole MOSFET, preferably one that's designed more for analog use than for...

Can anybody suggest a cheap, easily obtainable > = 400 V, < 2A thru hole MOSFET, preferably one that's designed more for analog use than for sub-ns switching. Thanks. I'm looking to squeeze a cathode follower into an existing vacuum tube amp and adding one MOSFET is easier than adding half a 12AT7.


MOSFET as shunt interface circuit

Started by Jan Panteltje in sci.electronics.design10 years ago 2 replies

Using a MOSFET as shunt works, but what if it is 'off'? I came up with this: in meter circuit . ...

Using a MOSFET as shunt works, but what if it is 'off'? I came up with this: in meter circuit . remote MOSFET power switch . ------------------------------------- . | | | . g 1k5 18k ...


JFET vs MOSFET

Started by Anonymous in sci.electronics.design1 year ago 38 replies

I am mostly an RF engineer , but our analog guy moved on and I am doing a little bit of sustaining of his stuff. In looking at one of his...

I am mostly an RF engineer , but our analog guy moved on and I am doing a little bit of sustaining of his stuff. In looking at one of his circuits I have gone back to the basics on JFET and MOSFETS. I am seeing that the basic electrical characteristics of a depletion MOSFET is similar to a JFET (I see the difference in enhancement MOSFET - ie - they are generally in an off state a


High-Side MOSFET gate driver voltage generation

Started by wolti_At in sci.electronics.design9 years ago 4 replies

Hello, I am looking for some advice for controlling an N-channel MOSFET (IPD64CN10N). Right now for testing I was using an IR2112 driver...

Hello, I am looking for some advice for controlling an N-channel MOSFET (IPD64CN10N). Right now for testing I was using an IR2112 driver which I already had available and a small isolation transformer. I do not like this because this is a) quite expensive and b) a not so elegant solution. My application is special in the case that the source of the MOSFET does not stay on a constant pote...


MOSFET specs

Started by Sylvia Else in sci.electronics.design2 months ago 11 replies

I was looking for a high voltage MOSFET with a low drain source resistance. I was considering...

I was looking for a high voltage MOSFET with a low drain source resistance. I was considering this: http://au.rs-online.com/web/p/mosfet-transistors/8647925/ I cannot reconcile the information given there. Figure 3 indicates that at 25 degrees, an Id of 5.5 amps and Vgs of 10V will give an Rds of about 320 milliohms. So go to Figure 8, and for the same conditions it gives an Rds of ...


PWM with low side MOSFET drive for DC motor (coast or brake when off?)

Started by Brandon in sci.electronics.design10 years ago 16 replies

I need to correct my understanding of a low side MOSFET switching for a DC motor. I have a DC motor in parallel with a diode connected to the...

I need to correct my understanding of a low side MOSFET switching for a DC motor. I have a DC motor in parallel with a diode connected to the drain of an n-channel MOSFET on one side (anode side of the diode) and the motor supply voltage on the other. When the MOSFET is switched on, the motor runs, and when it is switched on the motor coasts. However, I was under the impression that when t...


How about it? Experiments of the third kind , take 999999.

Started by Jan Panteltje in sci.electronics.design6 years ago 19 replies

How about it? Experiments of the third kind , take 999999. Update Hotplate design, stabilizing the heater MOSFET ...

How about it? Experiments of the third kind , take 999999. Update Hotplate design, stabilizing the heater MOSFET http://panteltje.com/pub/thermos_box_mounting_plus_heater_circuit_diagram_IMG_3415.JPG shows the quick sketch diagram of the MOSFET driver. The idea is that the current through the MOSFET is exactly proportional to the input voltage. As we all know, MOSFETs like to do t...


MOSFET Transconductance vs Drain Current

Started by John S in sci.electronics.design6 years ago 26 replies

This question is really prompted by the discussion on the thread "How to Bias a CS mosfet." In playing around with the possibilities, I noticed...

This question is really prompted by the discussion on the thread "How to Bias a CS mosfet." In playing around with the possibilities, I noticed that the MOSFET had an unreasonably high (ISTM) small-signal gain. So, I put most everything about biasing exactly to 1/2 Vdd aside to investigate. In the LTSpice circuit listed below, I can measure a small-signal gain of about 690. On the few d...


strange MOSFET failure mode

Started by Winfield Hill in sci.electronics.design1 year ago 10 replies

The subject MOSFET is a C2M0280120D, a serious 1.2kV SiC TO-247 MOSFET. The scope pic shows driving it with a -3.6 to +16.5V gate pulse, ...

The subject MOSFET is a C2M0280120D, a serious 1.2kV SiC TO-247 MOSFET. The scope pic shows driving it with a -3.6 to +16.5V gate pulse, 100ns long in this case, and it's switching a 50-ohm resistor from +200V, or 4A (part of my fast HV pulser project.) I previously had it making a burst of five 15ns-long 250V 5A pulses, and everything was fine, perfect. But after fooling ar...


ltspice -- body effect and other matters

Started by Michael Robinson in sci.electronics.design7 years ago 11 replies

I need to be able to model a mosfet with values of L, W, Vth, Kprime, lamba and gamma, and I'm trying to figure out how to do this with...

I need to be able to model a mosfet with values of L, W, Vth, Kprime, lamba and gamma, and I'm trying to figure out how to do this with LTSpice. Looking at ltspice mosfet models, they don't have a separate value for K. They have Cgs, W and L. K is a function of Cgs, W, L, and electron mobility. So I could sort of kluge my own mosfet model by choosing Cgs so that K comes out just right. ...


Mosfet switching times ?

Started by Hammy in sci.electronics.design7 years ago 20 replies

When Mosfet switching times are shown in the data sheets i.e ton,toff and tdelay. They specify an Rg value. Is this Rg value the...

When Mosfet switching times are shown in the data sheets i.e ton,toff and tdelay. They specify an Rg value. Is this Rg value the driver resistance or the internal mosfet mesh resistance? The reason I'm asking is that every FET sheet uses a different value of Rg for testing. The ones with the lower Rg have the quickest switching times. For example two similar devices a Fairchild http:...


A PIC based boost converter

Started by Jan Panteltje in sci.electronics.design6 years ago 2 replies

Updated the diagram for the 'on' and 'off' touch button MOSFET added. http://panteltje.com/pub/sc2_pwr_diagram_2_img_3235.jpg This MOSFET is...

Updated the diagram for the 'on' and 'off' touch button MOSFET added. http://panteltje.com/pub/sc2_pwr_diagram_2_img_3235.jpg This MOSFET is in a funny place, between the 2 batteries, this is to get enough drive once it is on. The BLACK button bridges the MOSFET, this starts the boost converter, then the PIC comparator senses if the battery is higher than 2.0V, if so it gives +5V to the M...


High side driving N-channel Mosfet with PWM

Started by Phil in Melbourne in sci.electronics.design10 years ago 19 replies

So I would have thought that this would be a simple problem but the more information I get the more I get confused...... I want to PWM...

So I would have thought that this would be a simple problem but the more information I get the more I get confused...... I want to PWM a whole lot of LEDs. The current consumption of the bank of LEDs is in the order of 15 Amps, at 12V. For reasons I won't go into, my only option is to use a high side mosfet. I have chosen an N-channel MOSFET (IRL3803) mainly because of its huge ...


N-chl MOSFET Jellybean??

Started by RST Engineering in sci.electronics.design6 years ago 6 replies

Anybody got a suggestion for an N-channel MOSFET power device (prefer TO-220 or similar) that Joe Hamhand can get in East Undershirt Ohio on a...

Anybody got a suggestion for an N-channel MOSFET power device (prefer TO-220 or similar) that Joe Hamhand can get in East Undershirt Ohio on a Sunday afternoon? Thanks, Jim


Measuring the Output Impedance of a (Large Capacity) Voltage Source

Started by Anand P. Paralkar in sci.electronics.design4 years ago 41 replies

Hi everyone, I am trying to test a MOSFET H-bridge at around 400V DC input. I need to observe the MOSFET Drain-Source waveforms for ringing...

Hi everyone, I am trying to test a MOSFET H-bridge at around 400V DC input. I need to observe the MOSFET Drain-Source waveforms for ringing during the on to off state (and vice versa) switching. I observe that the drain to source waveform is affected by the DC source that I use to supply in the input DC voltage to the MOSFET H-bridge. We have three different sources (including one ...


75332P MOSFET drain connected to which battery terminal?

Started by John Doe in sci.electronics.design6 years ago 18 replies

I have a 75332P MOSFET on a cordless drill controller heatsink. I guess it's part of a pulse width modulator. The drain (flange) connects...

I have a 75332P MOSFET on a cordless drill controller heatsink. I guess it's part of a pulse width modulator. The drain (flange) connects directly to one of the battery terminals. Does the MOSFET drain go directly to the battery minus/ground terminal? Or does it go to the battery plus terminal? Thanks. -- My application... I'm desperately trying to develop a better inline ...


MOSFET failure

Started by Michael in sci.electronics.design8 years ago 14 replies

I have a MOSFET consistently blowing up. 550V part, 230V in, buck configuration, transformer drive. The symptom is always the same: g-s measures...

I have a MOSFET consistently blowing up. 550V part, 230V in, buck configuration, transformer drive. The symptom is always the same: g-s measures short. What may be causing it? Is it gate drive overvoltage? Thanks