about MOSFET current mirror

Thread Starter

CantataAndAria

Joined Nov 14, 2014
11
1. The N-channel MOSFET given in datasheet is like this:
1.png

but the MOSFET N-channel current mirror in simulation software is like this:
2.jpg

I'm confused about the direction of the arrows and the G/D/S of pins. Can anyone explain briefly?


2. I have three MOSFETs of the same model. I built a small MOSFET N-channel current mirror. Assume the connection is correct (I'm not sure), the output current tested by using different pairs are very different.

LEFT RIGHT CURRENT (mA)
MOSEFET1 MOSFET2 119
MOSEFET1 MOSEFET3 13
MOSEFET2 MOSEFET1 0
MOSEFET2 MOSEFET3 0
MOSEFET3 MOSEFET2 76
MOSEFET3 MOSEFET1 3.9
Is this probably because one of the MOSEFETs is broken???
 

Alec_t

Joined Sep 17, 2013
14,210
The symbol depends on whether an enhancement mode or depletion mode MOSFET is shown. See, for example,
http://en.wikipedia.org/wiki/MOSFET
Which model MOSFET were you using?
Even different samples of the same model will probably have different gate-source threshold voltages, which may skew your current-mirror results.
 
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