Virtual short: as a result of the op-amp voltage magnification is very big, general general-purpose operational amplifier open-loop voltage magnification are above 80 dB, voltage and the output of the op-amp is limited, is in commonly 10 V ~ 14 V, so the differential mode of op-amp input voltage is less than 1 mV, two input nearly the same potential, the equivalent of "short circuit", the open loop voltage amplification factor, the greater the potential at the input to two equal the closer, "virtual short" refers to the analysis of the operational amplifier is in a state of linear, can consider the two input equipotential, this feature is called false short circuit, referred to as "virtual short, obviously can't be two real short circuit input end,
Virtual broken: due to the differential mode op-amp input resistance is very big, general general-purpose operational amplifier input resistance are more than 1 m Ω, so current into the op amp inputs is often less than 1 ua, far less than the input of the external circuit current, it can often be two op-amp input as open circuit, and the input resistance, the greater the two input the closer it gets to the open, "virtual broken" refers to the analysis of the op-amp is in a state of linear, can consider the two input equivalent open, this feature is called false way, referred to as "virtual broken, obviously can't will truly two input circuit,
On the analysis of the operational amplifier circuit working principle, the first please temporarily forget what synthetic amplifier, reverse amplifier, adder, subtracter, what is the differential input, temporarily forget the input/output relationship formula, to analyze the actual amplifier as ideal amplifier there will be no problem,
CodePudding user response:
This is not a question of
? Zha put in Chen Shuyun virtual virtual broken,