Thought I better read a bit 
Low impedance feedback it seem to be
And says that its often wrongly named as current feedback
If I understand what Nelson says, we should not take it for a given fact whenever current feedback is mentioned, that it may not be that at all
I guess current feedback just sounds more fancy for marketing
Low impedance feedback it seem to be
And says that its often wrongly named as current feedback
If I understand what Nelson says, we should not take it for a given fact whenever current feedback is mentioned, that it may not be that at all
I guess current feedback just sounds more fancy for marketing
In the example from JM plantefeve the 0.25ohm resistor serial connected with the speaker develops across itself a voltage which is an image of the current flowing through the speaker. The junction point of this resistor to the speaker is returned to the inverting input of the amp through a 100 ohm resistor. This is current feedback.
I have read somewhere that current feedback amps are less sensitive to cables and difficult loads
Is this true?
And is true current feedback really only a matter of a resistor?
I thought it was way more complicated
And also that current feedback introduce some complications, that may be less desired, despite its other theoretical advantages
So, what are the pros and cons?
Ahhh, now I know
I just realised that my very sweet Mirand amps are really current feedback design, which might explain a lot
Is this true?
And is true current feedback really only a matter of a resistor?
I thought it was way more complicated
And also that current feedback introduce some complications, that may be less desired, despite its other theoretical advantages
So, what are the pros and cons?
Ahhh, now I know
I just realised that my very sweet Mirand amps are really current feedback design, which might explain a lot
tinitus said:
A difference between voltage feedback and current feedback amps is:
- Voltage feedback amp produces a low output impedance.
- Current feedback amp produces a high output impedance.
Whenever the feedback voltage is proposional to output current, the circuit has current feedback.
In op amps, the non-inverting current feedback amp is called a "transconductance amplifier", and also called a "voltage-to-current converter" because an input voltage controls an output current.
Seems you mix up things:Babowana said:
http://en.wikipedia.org/wiki/Current-feedback_operational_amplifier
Point is, there is a difference between current feedback and current output, you are referring to the latter. Both have nothing to do with each other, you can make either current feedback or voltage feedback topologies to produce either current output or voltage output (or anything in between).
- Klaus
Hi Klaus,
Let's think about a non-inverting feedback op amp.
When we give an input voltage to the noninverting input, we arrange noninverting feedback voltage to the inverting input.
When we get the feedback voltage from the output voltage-sampling, we call it a "noninverting voltage feedback". Meanwhile, when we get the feedback voltage from the output current-sampling, we call it a "noninverting current feedback".
So,
Let's think about a non-inverting feedback op amp.
When we give an input voltage to the noninverting input, we arrange noninverting feedback voltage to the inverting input.
When we get the feedback voltage from the output voltage-sampling, we call it a "noninverting voltage feedback". Meanwhile, when we get the feedback voltage from the output current-sampling, we call it a "noninverting current feedback".
So,
- Noninverting voltage feedback: input voltage -> output voltage -> output voltage sampling (voltage feedback system) -> feedback voltage
- Noninverting current feedback: input voltage -> output current -> output current sampling (current feedback system) -> feedback voltage
A short drawing is better than a lon speach!
I see now why you call it: "non inverting...."
Mixed feedback can be nice when driving wideband high efficiency speakers or simply very light cones speakers which do not like high damping.
It permits to adapt precisely the amplifier output to the speaker.
I see now why you call it: "non inverting...."
Mixed feedback can be nice when driving wideband high efficiency speakers or simply very light cones speakers which do not like high damping.
It permits to adapt precisely the amplifier output to the speaker.
I perfectly see you point and all what you say (+ the drawing) is valid from the phenomenical standpoint, except that you chose to personally redefine the commonly accepted term in engineering that "current/voltage feedback" stands for. This only adds to confusion, especially for less experienced readers.Babowana said:
- Klaus