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Then do not use a Darlington pair as it will always have a comparatively high Vcesat (see 'disadvantages')-
What is your drive voltage? What is the max. drive current you can provide?
No. hfe is AC current gain, hFE is DC current gain when the transistor is an amplifier, not a switch and is NOT saturating. Most transistors saturate as a switch fairly well when the base current is 1/10th the collector current even if the hfe and hFE are very high.
If you use a BJT to switch a MOSFET, and the switching frequency is less tham about 10 KHz, the BJT might need only microamps of base current.
You can also find MOSFETs that will switch at 2.5V, though they might not handle your current requirements. Bit who kniows since you haven’t told us how mich current is needed nor how much current your 2,5V signal can source.
Bob
Would like to know who comes up with this trifle of which is upper case, often misused by even instructors... When Gain.dc or Gain.ac would say it...
Well, I was after around 0.3Vce sat conducting less than 0.5A to energize a circuit powered by a nearly discharged lithium cell from about 10 to 20mA base current... Is that asking too much ?
Have a look at this MOSFET: Vgsth <= 2.3 V.
Or use a 2-stage architecture:
The only disadvantage here is that the circut is inverting: a high level (2.5 V) at the input will turn Q1 off. If you cannot compensate for this e.g. in the driving circuit (or its software), add a third stage in front of Q2 to make the circuit non-inverting.
Or use a 2-stage architecture:
The only disadvantage here is that the circut is inverting: a high level (2.5 V) at the input will turn Q1 off. If you cannot compensate for this e.g. in the driving circuit (or its software), add a third stage in front of Q2 to make the circuit non-inverting.
Nice find... question... what is called logic level ? Are they generalizing ? Is it 5V logic; 3.3V logic; 2.5V... logic level ? Is it left to guessing for their product ? Shouldn't it be specified like "3.3V logic" ?Which brings another... what about level translator ICs handlig/performing from lower voltages ?
Like a level translator IC to drive larger loads ?
Instructors and books are often wrong. I find descriptions of hFE and hfe in datasheets.
When will everybody understand that the threshold G-S voltage of a Mosfet is when it BARELY turns on with a very low current that is so low that it is almost turned off??
When will everybody understand that the threshold G-S voltage of a Mosfet is when it BARELY turns on with a very low current that is so low that it is almost turned off??
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Should be obvious from Ids ~ (Vgs-Vth)², shouldn't it? Unfortunatley: who studies transistor model equations anymore today?
Without equaitions: that's what the graphs are for in a datasheet.
Graphs on a datasheet are for "typical" devices that you cannot buy, you get what is available. Devices with passing but minimum spec's are much worse and probably will not work if the circuit is designed with the graph numbers.
When I design a circuit I look at all minimum and maximum specs so that everything I make works perfectly.
When I design a circuit I look at all minimum and maximum specs so that everything I make works perfectly.
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