Hello,
So you are saying that it doesnt fully respond to the OP's question because there were no parentheses in the denominator?
I think that is very strange of you to say especially since R1 was factored out in later lines and the goal clearly pointed out. Perhaps you should re read my previous post.
It wasn't because of "no parentheses" in the denominator. You said:
"If we look at the denominator alone:
D=R2*R4*RL-R1*R3*RL+R1*R2*R4
we have a couple choices with the main goal is to get:
D=R2*R4*RL"
You then made D=R2*R4*RL, showing your choice with parentheses. You said:
"We can then factor out R1:
R1(R2*R4 -R3*RL)=0
and we are left with:
R2*R4 -R3*RL=0"
That choice leads to a relationship between Vin and IL, namely "IL=Vin/RL". This condition (R2*R4 -R3*RL=0) provides that for a fixed Vin, the current IL depends on the value of RL. This is not how a current source driving RL should behave.
The OP asked if the circuit was a "voltage dependant current source" and you didn't show the condition (R2*R4-R1*R3=0) for the current in RL to be independent of the value of RL. For this condition the relationship IL = Vin/R1 obtains; IL does not depend on the value of RL.
Also, for that independence to hold, given an ideal opamp and R2*R4-R1*R3=0, if we remove RL and calculate the driving point impedance at the node which drives RL (with the Vin node grounded), that impedance should be infinite--the output impedance of a current source.
The condition you analyzed (R2*R4 -R3*RL=0), while interesting in its own right, does not provide an (ideally) infinite impedance at the node which drives RL when RL is removed. For a fixed Vin the current in RL is not independent of the value of RL; it varies inversely as the value of RL.
The OP asked if the circuit was a "voltage dependant current source"; it seemed relevant to point out the condition which would make it so, which you did not do. That's what I was referring to when I said that you did not "fully respond" to the OP's question.
It still reads the same as when I first read it.
Hello again,
I see now what you are trying to get at, but you do have to realize that this circuit is never going to be a true voltage controlled current source, only a pseudo one because there will always be one trade off for another...you can't have both.
I assumed that if someone saw RL in the equation they would know right away that RL had to be constant, otherwise that condition could not be met. That should be obvious from the equation and also the circuit was drawn with a constant RL.
If you do want to impose a variable RL then we do have to impose different requirements, that's should be a given. No problem with that as far as i can see, except as the explained above trade off which may or may not be significant either way.
I have provided plenty of groundwork in my previous posts if you would like to take it farther that's fine with me.
Hello,
What does the phrase, "inverse impedance" mean to you? That means if you have Z and you have 1/Z when you multiply them together you get 1.
Since your circuit obviously does R^2/Z rather than 1/Z then you have to figure that R^2 in with it.
For example, with R=1k then R^2 is 1000k (1 meg), and if Z=100 then we have:
Zin=R^2/Z=1000000/100=10000, so with a 1v input source you should see 1/10000 amps flowing from the Vin source.
For Z either capacitance or inductance, you know that the cap is 1/(s*C) and the inductor is s*L. Notice that if you replace C with L or L with C you get the inverse of the other. Can you figure out what to do with Z being a cap or inductor now?
For more complex impedances (more elements involved in the impedance) you would have to do a little more work to figure out what to look for.
Remember when dealing with real life circuits like this to always check your limits. Output voltage, output current, etc. If the op amp can not handle some component values or the error introduced by a real life op amp is too high compared to the normal current or voltage values then the circuit will not behave nearly close to the theoretical and you might see wild results that appear to have nothing to do with the intended circuit. This is where lab experience or even careful spice analysis can be very valuable.
if Z being a cap or inductor , what i have to do is what u mention before just compare the phase shift of Vin and Iin right??
what u mean by the complex impedances is z include the combination of RLC??
if Z being a cap or inductor , what i have to do is what u mention before just compare the phase shift of Vin and Iin right??
what u mean by the complex impedances is z include the combination of RLC??
i have a question, is it the ground of the oscilloscope probe is shorted 2getther??
Let take an example,
**broken link removed**
For the circuit above, if i have 2 probe for the probe1 i put the ground at point B and probe tip at point A and probe2 ground at circuit ground and tip at point B then will short circuit R2??
so, the current will flow through R1 and then to the ground of the probe1 then directly to the negative terminal of the source and cause the reading or probe1 become 12V??
actually, gyrators are still used a lot. the most common use is in audio graphic EQ devices, where a filter is needed for each frequency band. since inductors are large and expensive, it's much easier and compact to use a gyrator in place of inductors for each filter. of course a some audio processing equipment is now being implemented with DSP chips, and the filters are implemented in software, but most graphic EQs on the market are still analog and use gyrators. gyrators are also used in a lot of RF equipment too, since an amp and a couple resistors and capacitors are cheaper than the copper coil they replace, at least in low-level signal work up to about 50Mhz. with the newer op amp technology which can produce op amps with 300-500Mhz bandwidth, expect the use of gyrators to increase.
Hello again,
Thanks for the pic. I'll have to take a look at it soon. Looks nice the way they did it. Would you happen to know the year in which it was designed?
looks like 2001 according to the date in the lower right...
a gyrator is a "special case" of the NIC. the "generic" NIC is a negative impedance at all frequencies, while a gyrator is actually a "negative capacitance".
i think what the OP was looking for was how the NIC behaves, and all the gyrator info was an unintended rabbit trail.
the usual way of measuring the output impedance of a signal source is to measure the open circuit voltage (Vo), then measure the voltage with a load (Vl). the difference in voltages and the known load impedance can be calculated to find the source impedance Zs=Zl((Vo/Vl)-1). a NIC across the source adds a negative Z to the source impedance and lowers the total source impedance. it acts as a kind of "helper" amplifier in parallel with the source.
a gyrator is a "special case" of the NIC. the "generic" NIC is a negative impedance at all frequencies, while a gyrator is actually a "negative capacitance".
i think what the OP was looking for was how the NIC behaves, and all the gyrator info was an unintended rabbit trail.
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