If use long length to set a MOS current mirror in saturation, then get a small current at output site, is it possible to make the output current = 15 ~ 30 nA ?
depend on process. You need to bias transistor in weak inversion. however when you design for small current your W and L value will be small. smaller device mean difficult to match.
If use long length to set a MOS current mirror in saturation, then get a small current at output site, is it possible to make the output current = 15 ~ 30 nA ?
If use long length to set a MOS current mirror in saturation, then get a small current at output site, is it possible to make the output current = 15 ~ 30 nA ?
From the first order, Idsat=0.5(W/L)(Vgs-Vt)^2,so there is two way you can get tiny Ids,namely,small W/L or low Vgs-Vt.For the former case, you have to use reasonable big L to satisfy W for matching.The latter is hard due to Vt variation,so have to make it reasonable big to reduce the error.
anyway,this is just first order consideration...Even you can get rid of two above issues,the large L small W mos is not typical for Vt parameter given by foundry,the Vt will varies due to geometric effect,you have to fix the error youself,just do test device tapout...
Maybe subthreshold can handle your requirement,but I don't know about subthreshold design,hoho
above are some of my thoughts,hope they are helpful
Added after 2 minutes:
sj95 said:
Dear all:
In simulation, we can produce the so small current easily.
But in a real situation, the so small current can flow in the path ?
Before the current reach its destination, it becomes zero because the leakage, doesn't it ?
Or in a switching circuit, the clock noise or glitch affects the current, then the current becomes trivial, and can't have normal function ?
even femto ampere current can be generated. please refer to paper "On the design and characterization of femtoampere current-mode circuits" by Bernabe Linares-Barranco and Teresa Serrano-Gotarredona.
If use long length to set a MOS current mirror in saturation, then get a small current at output site, is it possible to make the output current = 15 ~ 30 nA ?
Hi, wdd!
It seems your circuit is wrong.
Suppose left-side current is 1uA and resistor 1M.
Voltage drop on resistor should be 1V. In this case Vgs of right-side transistor is almost zero. So the current also zero. It is not a mirror.