alexyangfox
Newbie level 6
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Dear, all.
I don't quite understand what "Saturation" means for a BJT and a MOSFET.
So I Searched on the internet and wikipedia says,
"Saturated transistor, a BJT transistor or field-effect transistor that is fully turned on."
So I suppose that a fully turned ON transistor is saturated.
But then I met the problem below:
1.
let me say,it's an npn bjt.when the term,"turned on" ,is used , I think this means I should treat the npn bjt as a switch,and the switch is connected into a circuit .For the circuit ,it's a two-terminal device,and its two terminals are emitter and collector. At the same time ,the base terminal is a control terminal.
If the transistor is fully turned on , the resistor across the two terminals, the collector and the emitter , must be very small.
And in the Amplification region the resistor is very big , because the Curve is almost a horizontal line. ΔIc/ΔVbe is almost zero,and the reciprocal ,the resistor, is very big.
And in the left region, the Saturation Region,the Resistor is very small , and the term "Saturation Region"seems reasonable...
But for the NMOS case, I am so puzzled.
2. NMOS.
**broken link removed**
I treat the NMOS as a two terminal device in a circuit two.
The two terminals are the drain and the source.
And also the gate is for controlling the switch's operation.
When this Nmos is fully turned on , I suppose the resistor across the two terminals is very small too.
But when looking at the I-V curve, the region with the biggest resistors is called "Saturation Region."
I'm so puzzled..
Could anyone here help me with this problem...
Thanks in advance.
Regards.
Alex.
I don't quite understand what "Saturation" means for a BJT and a MOSFET.
So I Searched on the internet and wikipedia says,
"Saturated transistor, a BJT transistor or field-effect transistor that is fully turned on."
So I suppose that a fully turned ON transistor is saturated.
But then I met the problem below:
1.
let me say,it's an npn bjt.when the term,"turned on" ,is used , I think this means I should treat the npn bjt as a switch,and the switch is connected into a circuit .For the circuit ,it's a two-terminal device,and its two terminals are emitter and collector. At the same time ,the base terminal is a control terminal.
If the transistor is fully turned on , the resistor across the two terminals, the collector and the emitter , must be very small.
And in the Amplification region the resistor is very big , because the Curve is almost a horizontal line. ΔIc/ΔVbe is almost zero,and the reciprocal ,the resistor, is very big.
And in the left region, the Saturation Region,the Resistor is very small , and the term "Saturation Region"seems reasonable...
But for the NMOS case, I am so puzzled.
2. NMOS.
**broken link removed**
I treat the NMOS as a two terminal device in a circuit two.
The two terminals are the drain and the source.
And also the gate is for controlling the switch's operation.
When this Nmos is fully turned on , I suppose the resistor across the two terminals is very small too.
But when looking at the I-V curve, the region with the biggest resistors is called "Saturation Region."
I'm so puzzled..
Could anyone here help me with this problem...
Thanks in advance.
Regards.
Alex.