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 Driver cannot drive a MOSFET? or something wrong?

Started by Anonymous in sci.electronics.design9 years ago 12 replies

Here is my circuits, simple, yet, when I disconnect the MOSFET and load from the circuits, the waveform, duty cycle, amplitude, everything else...

Here is my circuits, simple, yet, when I disconnect the MOSFET and load from the circuits, the waveform, duty cycle, amplitude, everything else is correct. After I connect the mosfet and load (here I didn't use a laser diode, in stead I use a 1 ohm power resistor), all 're in a messy! MOSFET is hot coz it's not fully on, square wave form contains a lot of ringing, overshoot, duty cycle? no du...


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...


demultiplexer mosfet driver

Started by Jon Slaughter in sci.electronics.design8 years ago 3 replies

Do they make a mosfet pack that acts can be used as a demultiplexer? I need 6 mosfet drivers for a total of about 3A max, 6*0.5A, that can be...

Do they make a mosfet pack that acts can be used as a demultiplexer? I need 6 mosfet drivers for a total of about 3A max, 6*0.5A, that can be control like a demultiplexer. I would like to have this run at around 50Mhz. Unfortunately it needs to be high side mosfets with Vdrain about 3-5V and relatively low peak voltage drop across each of


MOSFET specs

Started by Sylvia Else in sci.electronics.design2 days ago 7 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 ...


Inverting vs NonInverting Mosfet Driver

Started by D from BC in sci.electronics.design8 years ago 10 replies

I have some fuzzy recollection of reading to the effect that noninverting mosfet drivers are more prone to instability due to layout...

I have some fuzzy recollection of reading to the effect that noninverting mosfet drivers are more prone to instability due to layout effects. Confirm? Just doing a quick sim in my head: With poor layout, when a noninverting mosfet driver turns on (sourcing), the signal ground pops up due to the mosfet gate capacitance (iirc called ground bounce?) then the driver sees a valid (actual...


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.design5 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...


Mosfet 7.5% increase in RDSON between 25C and 100C

Started by Hammy in sci.electronics.design8 years ago 6 replies

Anybody hear of a mosfet that only has a 7.5% increase in RDSON between 25C and 100C. Because according to ST the STD15NF10 is just such a...

Anybody hear of a mosfet that only has a 7.5% increase in RDSON between 25C and 100C. Because according to ST the STD15NF10 is just such a mosfet. I'm guessing this is a typo. Data sheet pg7 figure 11. http://www.st.com/stonline/products/literature/ds/7080.pdf


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...


spice Ver4 model - sync rec mosfet - body diode charge

Started by legg in sci.electronics.design7 years ago 17 replies

Some of you may be familiar with issues around self-synchronizing normally-off mosfet rectifier control. This is basically an attempt to get...

Some of you may be familiar with issues around self-synchronizing normally-off mosfet rectifier control. This is basically an attempt to get mosfets to behave as 'ideal' rectifiers, using the simplest control method - a linear negative Vds regulation in the third quadrant. Apart from the issue of accurately modeling the integrated version of a controller, the behavior of the mosfet body ...