Inverting Amplifier - Op-Amp Circuits
Input
Impedance of this module is Ri as pin 2 is at virtual ground, the opamp
with
feedback tries to maintain pin 2 and 3 at same potential pin 3 is at 0V
hence
pin 2 is at virtual ground. Clamping diodes protect OpAmp, Rf + Ri is
between
5kE and 1ME as an opamp may be able to drive around say 5mA max.
Current into node pin 2 = Vin/Ri if Vin is +ve it raises potential at
pin
2, in order to bring it to 0V the OpAmp sucks away the current by
turning
its output negative the current leaving pin 2 node is also Vin/Ri. Then
Vout
is given by Vin/Ri * Rf as per V=IR ohms law. Most OpAmps output swings
around
1v less than VCC/VDD for full swing use CA3130 this is a FET input
OpAmp, and has low bias currents in pico amps.
Vout = Vin * (-1) * (Rf/Ri)
Related Reading
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