Can imaginary and imaginary short be understood as both short circuits and open circuits at both the

Imaginary Short and Imaginary Break: Premise: Operational Amplifiers.

The output feedback is connected to the inverting input of the op amp (1) is imaginary short: u+=u- that is, the voltage of the inverting input and the inverting input is equal. Equal voltages are generally equivalent to short circuits, so they are called imaginary short.

Imaginary Break: i+=i-=0 The current leading to the input and inverting input is equal and both are 0i.e. there is no passing current.

The absence of current is equivalent to an open circuit. That's why it's called a virtual break. Encyclopedia explained:

Imaginary short and imaginary break are analog circuits.

Ideal integrated op amp.

Two important concepts. "Imaginary short" means that in an ideal situation, the potential of the two inputs is equal, as if the two inputs are shorted together, but in fact there is no short, which is called "imaginary short". Necessary conditions for hypocrisy.

It is the op amp that introduces deep negative feedback. An integrated op amp with ideal parameters is called an ideal integrated op amp. Its characteristics are:

Differential Mode Input Resistance rid = ; Open-loop differential-mode voltage gain aud = ; Output resistance ro = 0;Bandwidth fh = common-mode rejection ratio.

uo=aud(u+ —u-), which is composed of aud = = (u+ —u-)=uo aud=0 u+=u-, i.e., imaginary short. By rid = , there is no current at both inputs, i+=i-=0, i.e., a virtual break.

I also feel the same way, but I didn't find a similar conclusion.

Hypothetical shortness: Due to the large voltage amplification of the op amp, the open-loop voltage amplification of general-purpose operational amplifiers is more than 80 dB. The output voltage of the op amp is limited, generally at 10 V to 14 V.

As a result, the op amp has a differential mode input voltage of less than 1 mV, and the two inputs are approximately equipotential, which is equivalent to a "short circuit". The greater the open-loop voltage amplification, the closer the potential of the two inputs will be to equality. "Imaginary short" means that when the op amp is in a linear state, the two inputs can be treated as equipotential, a characteristic called a false short circuit, or virtual short for short.

Obviously, the two inputs cannot be truly short-circuited. The imaginary short leads to the conclusion that the positive and negative input terminals are equipotential.

False fault: Due to the large differential mode input resistance of the op amp, the input resistance of the general purpose operational amplifier is more than 1m. As a result, the current flowing into the op amp input is often less than 1UA, which is much smaller than the current in the external circuit of the input.

Therefore, the two inputs of the op amp can usually be regarded as an open circuit, and the greater the input resistance, the closer the two inputs are to the open circuit. "False break" means that when the analysis op amp is in a linear state, the two inputs can be regarded as equivalent open circuits, and this characteristic is called false open circuit, referred to as false breaks. Obviously, the two inputs cannot be truly disconnected.

The virtual break concludes that the current does not flow into the outflow amplifier input and that the external current is equal.

When analyzing the working principle of the op amp circuit, first of all, please forget about what co-amplification, reverse amplification, what adder, subtractor, and what differential input ......Forget about the formulas ...... the input-output relationship for a momentThese things will only interfere with you and make you more confused Please also ignore the input bias current, common-mode rejection ratio, offset voltage and other circuit parameters for the time being, which is something that designers need to consider. What we understand is the ideal amplifier (in fact, in repair and most design processes, it is not a problem to analyze the actual amplifier as the ideal amplifier).

Let's grab the two "plate axes" -- "virtual short" and "virtual break", and start to "cook Ding to solve the cow".

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Figure 1 op amp co-directional end grounding = 0V, reverse end and co-direction end are short, so it is also 0V, reverse input terminal input resistance is very high, virtual, almost no current injection and outflow, then R1 and R2 are equivalent to series, the current flowing through each component in a series circuit is the same, that is, the current flowing through R1 and the current flowing through R2 are the same. Current i1 = (vi - v-) r1 ......A current flowing through R2 i2 = (V- -Vout) R2 ......b v- = v+ = 0 ……c i1 = i2 ……d Solve the above junior algebraic equation and get vout = (-r2 r1)*vi This is the input-output relation of the legendary inverted amplifier.

After the operational amplifier is idealized, the amplification factor is infinite, and the output voltage is a finite value, which is converted to the input, and the input differential mode voltage is very small and negligible, and the input terminal voltage is considered to be short-circuited, that is, imaginary short. In addition, the ideal operation input resistance is infinite, and the operation input current is zero, that is, the virtual break. The premise of these two statements is that the operation is in a negative feedback state.

1. Different definitions.

1. Open circuit refers to the state that the circuit is not closed, or the wire is not connected, or the electrical appliance is burned out or not installed well (such as connecting the voltmeter in series in the circuit), that is, the whole circuit is disconnected somewhere.

2. Short circuit refers to the short circuit or part of the circuit. If the load and the power supply are connected by wires together, it is called a short circuit.

Second, the characteristics are different.

1. The short circuit is for a certain power supply point of the power system, reflecting some important performance of the point, such as the load capacity and voltage stability of the point, the strength of the connection between the point and the power supply of the power system, the level of the short-circuit current when the point is short-circuited, etc.

2. With the expansion of the capacity of the power system, the level of the system disconnection capacity will also increase. In the rated capacity of high-voltage switchgear, the short-circuit capacity has been changed to a break-circuit current value, such as the rated breaking current.

Third, the consequences are different.

1. Short circuit sometimes produces a large current of tens of thousands or even hundreds of thousands of amperes. As a result, a large amount of heat is generated, which damages the equipment and the arc melts many components in a short period of time. At the same time, the resulting current also brings a certain electromagnetic force, which can also damage the equipment.

It can also cause major fire and injury incidents.

2. The open circuit has interference suppression and destroys the stable operation of the system, and the line loss, heat loss, reactive power, etc. increases, which affects communication, communication and so on.

Virtual short circuit: refers to the part of the circuit that should be shorted, but the actual reliable connection is not completed.

Virtual open circuit: refers to the part of the circuit that should be disconnected, but the actual reliable disconnection is not completed.

Imaginary short: + and the terminal voltage are the same.

False Break: No current flows into or out of the amplifier at the + and terminals.

From the lower + end, u+=u2r2 (r2+r3) is obtained, and according to the imaginary shortness, u- u+ u2r2 (r2+r3).

From the above-end, I1=(U1 U-) R1 is obtained, and then the voltage of UF=I1RF is calculated, and then UO is calculated

Is it the imaginary shortness and disconnection in the analysis of integrated op amp circuits?

Imaginary short: refers to the fact that under the ideal circumstances, due to the characteristics of the open-loop amplification of the integrated op amp is infinite, even if there is a small voltage input between the inverting input and the inverting input terminal, the output will be amplified beyond the linear working area and distorted, so only the voltage at these two ends is 0, that is, the short circuit at both ends, can the integrated op amp work area. However, the reality is that the voltage at these two ends cannot be 0, but is very small and close to 0, that is, it is a virtual short circuit for the purpose of simplifying the analysis, referred to as imaginary short.

Virtual Break: Ideally, due to the infinite input resistance of the integrated op amp, the input terminal is broken, that is, the input current of the inverting input terminal and the inverting input terminal is 0, but the actual situation is that there is a large input resistance, so that the current at these two ends is very small and close to 0, that is, this is a virtual circuit break for the purpose of simplifying the analysis, referred to as virtual breaking.

"Imaginary short" means that due to the large voltage amplification of the op amp, the open-loop voltage amplification of general-purpose operational amplifiers is generally more than 80 dB. The output voltage of the op amp is limited, generally at 10 V to 14 V. As a result, the op amp has a differential mode input voltage of less than 1 mV, and the two inputs are approximately equipotential, which is equivalent to a "short circuit".

The greater the open-loop voltage amplification, the closer the potential of the two inputs will be to equality. But it's not really a short circuit.

Both are essential and equally important, and there is no one that is derived.