Gasboss775
Member
I built a simple voltage regulator, see attached, using a tl431 fed by a jfet wired as a current source and an npn buffer transistor.
I carried measurements of output resistance using the formula; Rout = ∆V/∆I. With loads between 0 and 125mA the output resistance was in fact negative, that is the output voltage actually increased ( albeit marginally ) as more current was drawn. Above 125mA it started to behave as would've been expected, that is a drop in output voltage under increasing current draw.
Can anyone explain this behaviour? I'm concerned that negative resistance could cause spurious oscillations.
I carried measurements of output resistance using the formula; Rout = ∆V/∆I. With loads between 0 and 125mA the output resistance was in fact negative, that is the output voltage actually increased ( albeit marginally ) as more current was drawn. Above 125mA it started to behave as would've been expected, that is a drop in output voltage under increasing current draw.
Can anyone explain this behaviour? I'm concerned that negative resistance could cause spurious oscillations.