MOSFET logic level question
MOSFET logic level question
(OP)
Hi,
What determines if a Mosfet is logic level or not?
Is the VGS or the Gate Threshold Voltage?
For instance the IRF7314 from IRF as a VGS of +/-12V
and a Gate Threshold Voltage (minimum) of 0,7V. (maximum is not show on the datasheets)
This device is not advertise as logic level. But I belive it is.
Help please?
Thanks
What determines if a Mosfet is logic level or not?
Is the VGS or the Gate Threshold Voltage?
For instance the IRF7314 from IRF as a VGS of +/-12V
and a Gate Threshold Voltage (minimum) of 0,7V. (maximum is not show on the datasheets)
This device is not advertise as logic level. But I belive it is.
Help please?
Thanks





RE: MOSFET logic level question
RE: MOSFET logic level question
You could probably use your device in a circuit, and it would probably work, but that would only be due to the fact that most circuits have ample noise margin.
But, you could get burned if the circuit design is marginal or overly noisy, particularly at high ambient temperatures.
TTFN
RE: MOSFET logic level question
RE: MOSFET logic level question
Example: ON Semiconductor calls MOSFETs that are specified at a gate voltage of 5 V "logic level".
Fairchild specifies gate voltages of 2.5 and 4.5 V as "logic level".
Standard MOSFETs are normally specified at 10 V gate voltage.
The threshold voltage is not a useful parameter here.
Regards.
RE: MOSFET logic level question
There are really two points of interest, the initial gate threshold where it begins conduction, and the gate voltage at which it will reach it's lowest specified Rds on. Temperature may sometimes be significant too.
A low gate threshold will be an advantage if you only have five volts to drive the gate, and you need be able to reach a very low turn on resistance for heavy loads.
But a low gate threshold will make it slower to turn off.
The only real advantage of logic level mosfets is that all the figures on the spec sheet are guaranteed with only a five volt gate drive signal. If you need full speed and power capability, the logic level mosfets are the safe way to go. But in low power, slow, or non critical applications, ordinary garden variety mosfets will often be perfectly o/k.
RE: MOSFET logic level question
the specification if you know what you are doing.
E.G. I often used as ECL pull-down 10 to 20 Kohm to
- 15 V.( it acts as a pulse stretcher, speeds up rising and
delays falling edge.)
<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032
RE: MOSFET logic level question
I think that I will change my circuit to use IRL series of mosfets (logic level). Better safe than sorry. Two SOT 23 mosfets are cheaper(!) than one pair in SO8 package.
It's amazing how a tiny SOT23 package can deliver 4.3 Amps
in 4.5V ! (I will use only 2A).
I will go for the IRLML6401 (VGS +/-8v).
Thanks all.
Morcego
RE: MOSFET logic level question