As we know in JFET or MOSFET there is a triode or Linear region, Where for a fixed gate-source voltage, increasing drain source voltage is equivalent to applying drain source voltage across a resistor (approximately) . My question is whether there is a similar region for BJT in which the bjt would work as if its a resistor, though I know only about cut-off, active, and saturation region in BJT.
Electronic – BJT triode region
bjt
Best Answer
As @Brian says, in the saturation region this is true. The transistor has a dynamic resistance (for very small voltage changes) of approximately Vt/Ib.
So, for example, the collector of an NPN transistor with 50uA of base current will behave approximately like a 500 ohm resistor to ground for very small voltage changes (mV or less) that are AC-coupled. Remember that dynamic resistance is \$r_d=\Delta V/\Delta I\$.
simulate this circuit – Schematic created using CircuitLab
For larger voltage changes the nonlinearity will become very obvious.