throbscottle
Well-Known Member
I learnt this kind of thing in college, but it was so many years ago I've forgotten, and need someone to check my reasoning please! This is relevant to op-amp bias current and noise, but I'm using knife-and-fork values to check I've got the theory right.
Suppose I have two resistors in series, 9Ω and 1Ω, call the connection node A. Connect 10v across the ends of the two resistors, the 1Ω end being 0v, so 1 amp flows, voltage at A is 1v. Connect a constant current to node A. It can either source or sink, but say source because it's easier to think about. Say it's 100mA.
Am I correct in thinking that the current from the constant current source (or sink) sees the 2 resistors as though they are in parallel? So the 9Ω resistor sees 1A - 90mA = 91mA, and the 1Ω resistor sees 1A + 10mA = 1.01A ???? So the voltage at node A is 1.01V?
I've always kind of fudged around questions like this, taking the experimental approach, these simple R/V/I theoretical networks were confusing enough in class and long since forgotten, but suddenly I need to re-learn it. All help appreciated!
Suppose I have two resistors in series, 9Ω and 1Ω, call the connection node A. Connect 10v across the ends of the two resistors, the 1Ω end being 0v, so 1 amp flows, voltage at A is 1v. Connect a constant current to node A. It can either source or sink, but say source because it's easier to think about. Say it's 100mA.
Am I correct in thinking that the current from the constant current source (or sink) sees the 2 resistors as though they are in parallel? So the 9Ω resistor sees 1A - 90mA = 91mA, and the 1Ω resistor sees 1A + 10mA = 1.01A ???? So the voltage at node A is 1.01V?
I've always kind of fudged around questions like this, taking the experimental approach, these simple R/V/I theoretical networks were confusing enough in class and long since forgotten, but suddenly I need to re-learn it. All help appreciated!