BJT or MOSFET for Current Source Circuit

Started by panfilero in sci.electronics.design8 years ago 28 replies

I'm looking to make a "Current Source" I'd like to supply a maximum of 10A, I'm thinking about putting a transistor at the output of an Op-Amp and...

I'm looking to make a "Current Source" I'd like to supply a maximum of 10A, I'm thinking about putting a transistor at the output of an Op-Amp and using the transistor to pull the 10A through my load. My question is, would I be better off using a MOSFET or a BJT for this (darlington or maybe even IGBT) it really just has to sit there and handle 10A... does this point towards which transistor ha...


Around 30V Mosfet that can handle 30V Vgs

Started by Klaus Kragelund in sci.electronics.design6 years ago 26 replies

Hi I am looking for a N channel and P channel MOSFET with about 30V drain source and a gate that can handle +/- 30V gate source I found a...

Hi I am looking for a N channel and P channel MOSFET with about 30V drain source and a gate that can handle +/- 30V gate source I found a few on Digikey.com, but there's no parametric search for that parameter Anyone got a part to recommend? Cheers Klaus


Proper linear MOSFET for HV load

Started by Piotr Wyderski in sci.electronics.design3 years ago 28 replies

Hi, what MOSFET (or several of them) would be good for an electronic load rated for limiting values 650V/50A/1kW (whichever applies first)?...

Hi, what MOSFET (or several of them) would be good for an electronic load rated for limiting values 650V/50A/1kW (whichever applies first)? Purely linear operation -- I remember you were saying that ordinary switching FETs aren't good for that purpose. Would SiC FETs work? I like both their high voltage and low R_DS_ON for high-current mode. I think that the best backage would be TO-2...


fet for automatic gain control?

Started by Hul Tytus in sci.electronics.design8 years ago 31 replies

sci.electronics.design fet for automatic gain control? Any suggestions for an enhancement mode mosfet to serve as a variable resistence...

sci.electronics.design fet for automatic gain control? Any suggestions for an enhancement mode mosfet to serve as a variable resistence element in an automatic gain control type circuit? Power involved is a bare whisper; worst case voltage is probably 30 volts. There may well be a better remidy than an mosfet, but it looks good at this point. Hul


Dual low gate drive mosfet

Started by bitrex in sci.electronics.design8 years ago 4 replies

Needed: Dual p channel/n channel low gate drive (~2 volts) MOSFET, very low on resistance, for supply switching application. Max DC current in...

Needed: Dual p channel/n channel low gate drive (~2 volts) MOSFET, very low on resistance, for supply switching application. Max DC current in the application will be about 500 mA. Any suggestions?


Power MOSFET SPICE modelling

Started by Glenn in sci.electronics.design8 years ago 2 replies

How can they SPICE model two distinct serially connected resistors (Rls, Rcs - respectively Rll, Rcl) inside a power MOSFET? Are they kidding us...

How can they SPICE model two distinct serially connected resistors (Rls, Rcs - respectively Rll, Rcl) inside a power MOSFET? Are they kidding us ;-) If so is that useful in the model?: A Low-Cost Class-E Power Ampli?er with Sine-Wave Drive - Caltech: http://www.its.caltech.edu/~mmic/reshpubindex/papers/ClassE.pdf (pdf-page 3) - Is it possible (how?) to measure the internal paras


fast, small low-capacitance zener to protect MOSFET gates

Started by Winfield Hill in sci.electronics.design3 years ago 28 replies

I became discouraged of finding a suitable low-capacitance zener to protect the MOSFET gates in my high-voltage amplifier designs. (The...

I became discouraged of finding a suitable low-capacitance zener to protect the MOSFET gates in my high-voltage amplifier designs. (The protection may be optional, but one sleeps better with it in place.) Even the 50uA-rated low-current zener diodes are in fact larger-die types, with high capacitance. For example, the 7.5-volt MMSZ4693 has about 130pF at zero volts. My solution was to us...


AC-line supplies - under 1% loss

Started by Winfield Hill in sci.electronics.design2 years ago 27 replies

TI's TIDA-00961 PFC reference design, see link: http://www.ti.com/tool/TIDA-00961 is for a 1.6kW offline PFC stage, with a goal of under 1%...

TI's TIDA-00961 PFC reference design, see link: http://www.ti.com/tool/TIDA-00961 is for a 1.6kW offline PFC stage, with a goal of under 1% total loss. In place of the customary diode bridge there's a totem-pole bridgeless PFC. It has two GaN half-bridge MOSFET boost-converters, plus a Silicon MOSFET active rectifier. They include a bridge rectifier, but it's bypassed by MOSF...


n-channel enhanecement MOSFET: why is it called an n-type inversion layer?

Started by Veek M in sci.electronics.design7 years ago 2 replies

In this MOSFET we have a p-type substrate, and n+ source/drain. When we apply a +ve voltage to the Gate, we repel holes (the majority charge...

In this MOSFET we have a p-type substrate, and n+ source/drain. When we apply a +ve voltage to the Gate, we repel holes (the majority charge carrier) in the p-type substrate downwards, thus uncovering fixed acceptor ions/atoms which are now negativly charged (electrons in the substrate are drawn to this region under the Gate). We thus create a layer of fixed negative ions (a acceptor ...


FM transmitter Repair

Started by amdx in sci.electronics.design4 years ago 10 replies

HI guys, I have attempted a repair on an FM transmitter. I replaced TR2,(shorted) VR1,(10.7 V output, VR1 is a SMD L78L09), and R4, it...

HI guys, I have attempted a repair on an FM transmitter. I replaced TR2,(shorted) VR1,(10.7 V output, VR1 is a SMD L78L09), and R4, it looked overheated, measured OK. I fired it up and then found the output Mosfet (F1)shorted and VR1 with an output of 11.2V. So I replaced the Mosfet and the L78L09. The unit works, output is good. However, the 9 volt regulator again has 11.2 v o...


AoE x-Chapters, 1.5kV 1us precision ramp

Started by Winfield Hill in sci.electronics.design2 years ago 2 replies

Here's an interesting circuit problem, make a precision 1.5kV 1500V/us ramp, good to...

Here's an interesting circuit problem, make a precision 1.5kV 1500V/us ramp, good to 1%. https://www.dropbox.com/s/yo6njt3rzfe85mu/3x.20_Precision-1.5kV-1us-Ramp_WH.pdf?dl=1 It features a HV MOSFET current source with a feedback circuit to maintain a constant output slew rate. Related to the thread, "op-amp-controlled MOSFET cucrrent-source", the circuit uses a BUF634 gate dr...


Backfed MOSFET current limit

Started by Tim Wescott in sci.electronics.design8 years ago 26 replies

Got a circuit. I'm using a high-side P-channel MOSFET to prevent damage when the battery is put in backwards. The FET is put in "backwards"...

Got a circuit. I'm using a high-side P-channel MOSFET to prevent damage when the battery is put in backwards. The FET is put in "backwards" (battery to drain, circuit to source) to point the body diode in the correct direction. When the battery is inserted, a capacitor on the circuit side of the FET charges up, sucking a considerable amount of current very briefly. The current is b...


MOSFET "Backwards" Current / Motor anti-generate

Started by Tim Wescott in sci.electronics.design9 years ago 19 replies

In 4-quadrant switching amplifiers, it's quite common to run current through a MOSFET "backwards" when it is on -- i.e., to run an NMOS with...

In 4-quadrant switching amplifiers, it's quite common to run current through a MOSFET "backwards" when it is on -- i.e., to run an NMOS with the current traveling from source to drain, instead of drain to source. Yet all the data sheets only show 1st-quadrant conduction, with current (for an NMOS) running from drain to source. Which boils down to my real problem: I'm working on a motor...


Design Battery Charger using H-bridge Mosfet concept

Started by samson.bunty1986 in sci.electronics.design9 years ago 10 replies

Hi, Am planing to design a battery charger using H bridge mosfet configuration . Battery spec as follows: Battery voltage ---24V Battery...

Hi, Am planing to design a battery charger using H bridge mosfet configuration . Battery spec as follows: Battery voltage ---24V Battery capacity -- 45Ah So the charging current should be 10% of battery capacity. am i correct?? So the charging current is 5A. Am having some querys. What are the mosfets hve to be used?? Is it 2 N-channel & 2 P channel mosfets?? How to controll th...


(LT SPICE ) i need hlep

Started by Tech-electro in sci.electronics.design7 years ago 1 reply

Hi my problem is hoe i can find Q-point of amplifier mosfet

Hi my problem is hoe i can find Q-point of amplifier mosfet


MOSFET Q???

Started by Anonymous in sci.electronics.design3 years ago 34 replies

What is the difference in the BEHAVIOR in the circuit of lateral and vertical MOSFETS. This is an audio application.

What is the difference in the BEHAVIOR in the circuit of lateral and vertical MOSFETS. This is an audio application.


Improved LineSupply

Started by Jamie in sci.electronics.design9 years ago 2 replies

Some one pointed out that my Mosfet was generating heat.. I fixed that. :) improved version, the MOSFET now switches full on. Version...

Some one pointed out that my Mosfet was generating heat.. I fixed that. :) improved version, the MOSFET now switches full on. Version 4 SHEET 1 880 680 WIRE 528 -64 304 -64 WIRE 544 -64 528 -64 WIRE 640 -64 608 -64 WIRE 704 -64 640 -64 WIRE 640 -32 640 -64 WIRE 304 -16 304 -64 WIRE 304 -16 240 -16 WIRE 368 -16 304 -16 WIRE 528 0 528 -64 WIRE 240 32 240 -16 WIRE 368 32 368 -16 WIR...


If you can't find a MOSFET big enough

Started by Piotr Wyderski in sci.electronics.design1 year ago 4 replies

Some people seem to have way too much spare time: https://www.youtube.com/watch?v=So-6lgmVhA0 Best regards, Piotr

Some people seem to have way too much spare time: https://www.youtube.com/watch?v=So-6lgmVhA0 Best regards, Piotr


Can I parallel mosfet dip relays?

Started by unk in sci.electronics.design6 years ago 14 replies

space/weight/price considerations make me wonder if I can stack two or more dip4 relays.

space/weight/price considerations make me wonder if I can stack two or more dip4 relays.


Depletion-mode P-channel MOSFET

Started by Piotr Wyderski in sci.electronics.design3 years ago 6 replies

Why such a thing does not exist in nature? I'd find several applications of such a beast. Of a P-channel complementary to LND150,...

Why such a thing does not exist in nature? I'd find several applications of such a beast. Of a P-channel complementary to LND150, especially. Best regards, Piotr