R
[email protected]
 Jan 1, 1970
 0
Interview question*
/\/\/\/\
 b 
\/\ 
 \___________
+/
 /




Q:What is the input "impedance" at b?
A:Very low because it is a virtual earth.
Q:So how much current would you expect to flow into it?
A:Very little because opamp inputs take "no current".
Q:So if it takes very little current, what is the "impedance"?
A:High?!
Q:But you just said it was low, if the gain of the opamp is 100,000
and the feedback resistor is 10,000 ohms, what is the "impedance" at
b?
Robin
*not original: from a magazine, possibly a reader's letter, 19791980?
/\/\/\/\
 b 
\/\ 
 \___________
+/
 /




Q:What is the input "impedance" at b?
A:Very low because it is a virtual earth.
Q:So how much current would you expect to flow into it?
A:Very little because opamp inputs take "no current".
Q:So if it takes very little current, what is the "impedance"?
A:High?!
Q:But you just said it was low, if the gain of the opamp is 100,000
and the feedback resistor is 10,000 ohms, what is the "impedance" at
b?
Robin
*not original: from a magazine, possibly a reader's letter, 19791980?