Auto Mesureing Device of FET VTO

101

01:15:18

VTO is the threshold voltage of Vgs of FET.This device can measure it automatically. Actually the measured value is slightly(about 0.24V)  higher than the true VTO.　This is  the apparent VTO included with true VTO and Relay activation voltage.. Width and length of channel were set　unlikely lrbel　for large Id. I made this device on breadboard and confirmed the basic function.  

published 9 years ago

hurz

9 years ago

Set relay inductance to 1pH and resistance to 1kOhm. Vt is then measured with 2.07V. Anyway do you belief this could be a real circuit? In simulation i would just lookup the protperties ;-)

ono

9 years ago

I made this circuit for “Simple Timer for Soldering Iron” witch I made about 3 weeks ago, to know the Vgs for relay-on. Yes, I know that the apparent VTO measured by this device is not the true VTO itself. But this circuit is suitable for my purpose. I really made this circuit on breadboard and I could measure the apparent VTO. For example, the “VTO” of BS170 and 2N7000 ware measured as 2.51V and 1.96V each. From this measured value I could calculate the off-time of “Simple Timer for Soldering Iron” and it was very near to the real off-time.

hurz

9 years ago

Just take your DMM for a simple test. Switch to "diode measurement" mode and connect Drain,Gate with plus probe. Source with minus probe. If your DMM can handle a high enough threshold voltage (at least 3V) it should give you a rough estimation about Vto. I tested it for BS170 and it gave me 2.1V, which is according to the datasheet not to bd. Anyway the Vto is a value mostly with a wide range from e.g. several 100mV to 2 or 3V min max range. Hope this helps.

add comment in editor

EveryCircuit is an easy to use, highly interactive circuit simulator and schematic capture tool. Real-time circuit simulation, interactivity, and dynamic visualization make it a must have application for professionals and academia. EveryCircuit user community has collaboratively created the largest searchable library of circuit designs. EveryCircuit app runs online in popular browsers and on mobile phones and tablets, enabling you to capture design ideas and learn electronics on the go.