How should be described and appellation is certain the feedback of the type, this problem is perplexing me all the time. This is a kind of dull idle dream not just. I know the ” of “ flames of war that makes public once at least, caused cause I think even if from inside these feedback features derivative wrong inference.

 

So, what is feedback after all? A kind of answer is it shows is a kind of process, detect namely some kind of signal that wants an influence, a certain bits when go to one of part feedback in circuit in front, can bring to bear on thereby some kind of control. Graph 1 show 4 kinds of when gave line of two kinds of signal classical circuit: The feedback of amplifier and drive. We say feedback source or is paralell connection derives (laden the voltage of two end) , or is series connection derives (the electricity that carries load, expression is the impedance that establishs ties with load the voltage of two end) .

 

We still speak of series connection and shunt-wound feedback, among them signal and incentive signal series connection or paralell connection. In “ paralell connection ” circumstance falls, two signal are inputting upright assemble instead, blame input termination ground instead. In “ circumstance of series connection ” falls, drive brings to bear on to be not input end instead and feedback to input end instead. Notice my scale and the means that appoint Sp of incentive signal source and Sm are a little ambiguous please, I am intended so do, because they are original,be unfavorable. My means, they can be considered as the ideal voltage source that establishs ties with impedance, or as shunt-wound as impedance ideal current source.

 

Graph 1: 4 kinds of of course of two kinds of signal classical circuit.

 

Pursue in light of now 2. Choose proper impedance to be worth Zt and Zb, and Sp of source signal n and Sm, we can implement a plan 1 in the random of 4 circuit. We use a figure now 2 in more general circuit.

 

Graph 2: Use more general circuit.

 

The first kind of condition that we should treat is series connection application (with derive the kind has nothing to do) . Source Sp is had be not 0 output, and Sm is 0 output. Accordingly, sm just passes his the reachs the ground join of inherent impedance Zm. Amplifier output sends electric current through Rf-Rg-Zm network. True operation amplifier, for instance the TL072 of old brand, can accept input electric current to be the circumstance of 0 almost. Like all operation amplifier, the signal output that its input class is the electric current that controls its finally to output voltage. Below this kind of circumstance, electric current comes from operation amplifier itself, suffer two (drive and feedback) the control pressing difference between input voltage. On the tradition, this is voltage feedback apparently, signal of a voltage is arrived to input end instead by feedback, undertake controlling over. In this reference point, the electric current that enters amplifier is negligible not plan.

 

Paralell connection feedbacks in light of now. Let us retroflexion signal source, namely Sm is had now be not 0 output, and Sp is cleared. Think back to, paralell connection application is feedback of the electric current that be called. I ask you now: Want to change the range of signal source only, can we transform the feedback type in circuit? Assume two signal source has be not 0 output, so do we still have voltage and voltaic feedback? Hypothesis is two 0, do we still feedback? (if the output stability of operation amplifier controls meeting effectively in 0V,strike back of course this conclusion! )

 

Is this voltaic feedback?

 

We continue. Does this electric current feedback (? ) input amplifier (influent electric current is negligible, right? ) bypass, stop in signal source Sm. If the specific value of network and Sm impedance is very great, so any effects that it produces are negligible not plan. This or voltaic feedback? I think is not. Contrary, it is voltage feedback, its operation amplifier inputs voltage to be in 0 n and the state that approach 0 n now, but the n that wants the n of Sm to be close to Sp only, their press difference to keep basically consistent (this is very important to this operation amplifier) .

 

If this returns insufficient conviction, can mix Rf, Rg so the impedance of Sm is double. We just will shed the voltaic halve of these parts of an apparatus. Accordingly, the electric current of the tentative idea feedbacks also must halve. However the change that the output of circuit still does not have materiality. Accordingly, it won’t suffer the effect that electric current feedbacks.

 

So, has voltaic feedback happened really? Of course. We replace TL082 with a different operation amplifier, its input class (signal electric current) output is inputted instead through its, come from operation amplifier external some dot. To the feedback part of signal, it is the output of operation amplifier this bits. Any parts of an apparatus that input join of one or more emitter end to this almost accord with a requirement (SSM2019 is a kind of choice, the is CFA voltaic feedback amplifier that says inside course of study is another kind of choice) . Almost all the parts of an apparatus that enters emitter can be in the some dot of operation amplifier interior exits its related market electric equipment, comprise the output that should input the output of class and decides amplifier. Use configuration of paralell connection application, amplifier still carries network drive electricity, stop in source Sm (below most circumstance) . But this, one fraction of electric current is shucked by “ ” feedbacks of operation amplifier input end instead, bring to bear on to the output of parts of an apparatus thereby wants control. Of course, this is voltaic feedback, because it accords with the persistent demand of paralell connection application.

 

Finally, return the case of series connection application, the job of operation amplifier is changeless still of course. Actually, the signal electric current that inputs class output still comes from amplifier the output that exterior —— comes from operation amplifier only. To see better Hunan, the circuit that will input end to see instead replaces for circuit of the equivalent austral Daiwei: Through a block the value is Rf•The resistor make a present of of Rg / (Rg + Rf) enters voltage Vout•The signal source of Rg / (Rg + Rf) . The output electric current that I think this remains amplifier of voltaic feedback —— to input class originates operation amplifier is outputted through the attenuation of singular resistance.

 

You may argue say, SSM2019/CFA amplifier inputs voltage to needing branch very sensitive still, because this remains voltage feedback parts of an apparatus (exclusive impossible means is, if its are low,input impedance instead for 0, won’t appear below this kind of circumstance input voltage is poor) . But if we agree with this argument, there is between the input end that we also must admit TL082 so very big but finite still impedance. This is meant electricity can produce between these inputs, because this TL082 is voltaic feedback parts of an apparatus!

 

This kind of inference is have not a leg to stand on. Contrary, I suggest according to feedback the type has classified method to circuit, it is the current source that inputs class to coming from amplifier undertakes an analysis. If current source is to be inside operation amplifier, carry feedback from output without electric current actually, operation amplifier and circuit work with voltage feedback necessarily. If current source comes from operation amplifier external input end instead, we think this is voltaic feedback.

 

As a result of a variety of accounts that above mentions, we should correct “ series connection to apply is voltage feedback from beginning to end, paralell connection application is voltaic feedback ” from beginning to end such viewpoint. It is voltage feedback or voltaic feedback, depend on the amplifier of circuit, is not his circuit develop attacks.

 

The article is reprinted design from electronic technology.