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Soclof said "Norton operational amplifier...produce an output voltage for the amplifier that is proportional to the difference between the two input currents". So the Norton amplifier is a current-controlled voltage source (CCVS).
Is it true that a CFB op-amp has a range of recommended resistor values for the feedback network in order to minimise offset and/or maximise bandwidth? If yes, then is this point worth including in the article? Rohitbd 12:43, August 16, 2005 (UTC)
Actually the Bandwidth of Current Feedback Amplifiers is not larger than that of a VFA. The main difference is that the CFA does not have a constant GBW (gain bandwidth product) but rather a constant bandwidth. However it is not correct (at least the way I understand it) to claim it has a higher bandwidth than a comparable VFA. Steve110 07:20, 17 March 2007 (UTC)
I see some changes were made, but the main premise that CFB are higher bandwidth devices was not changed. This is simply wrong. The Bandwith of a CFA of comparable VOL is the same. The main difference to a VOA is the way these things are looked at. Steve110 22:24, 26 March 2007 (UTC)
According to Bruce Carter of the Advanced Linear Products division of Texas Instruments...
"The bandwidth specification given in op amp data sheets refers only to the point where the unit gain bandwidth of the device has been reduced by 3 dB by internal compensation and/or parasitics -- not very useful for determining the actual operating frequency range of the device."
"Internally compensated, voltage feedback amplifier bandwidth is dominated by an internal 'dominant pole' compensation capacitor, resulting in a constant gain/bandwidth limitation. Current-feedback amplifiers, in contrast, have no dominant pole capacitor and therefore can operate MUCH MORE CLOSELY TO THEIR MAXIMUM FREQUENCY AT HIGHER GAIN [emphasis added]. Stated another way, the gain/bandwidth dependence has been broken."
I believe the point Mr. Carter is making is that when you are using a gain significantly greater than 1, the CFA OP Amp has a significant advantage over the VFA Op Amp in terms of much greater frequency response.
Perhaps the article could be updated to reflect this? —Preceding unsigned comment added by 58.10.65.22 ( talk) 13:03, 11 January 2009 (UTC)
I believe the schematic diagram should show a resistor in parallel with Cs, as it is that internal resistor that determines the transimpedance gain of the I to V converter section. — Preceding unsigned comment added by 174.91.201.72 ( talk) 17:09, 1 September 2011 (UTC)
US3944906 "NORTON type current responsive operational amplifier" http://www.google.com/patents/US3944906 ? -- J. D. Redding 04:52, 28 August 2012 (UTC)
I came here to learn about the current-feedback architecture, so I'm not really qualified to make changes. But I believe that pink-outlined stage in the schematic should be called, simply, a voltage buffer. The triangle has a high impedance input and a low-impedance output whose voltage tracks the input, correct? That's not a "current amplifier", as stated in the graphic. Spiel496 ( talk) 18:51, 22 January 2021 (UTC)
![]() | This article is rated Start-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | ||||||||||
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Soclof said "Norton operational amplifier...produce an output voltage for the amplifier that is proportional to the difference between the two input currents". So the Norton amplifier is a current-controlled voltage source (CCVS).
Is it true that a CFB op-amp has a range of recommended resistor values for the feedback network in order to minimise offset and/or maximise bandwidth? If yes, then is this point worth including in the article? Rohitbd 12:43, August 16, 2005 (UTC)
Actually the Bandwidth of Current Feedback Amplifiers is not larger than that of a VFA. The main difference is that the CFA does not have a constant GBW (gain bandwidth product) but rather a constant bandwidth. However it is not correct (at least the way I understand it) to claim it has a higher bandwidth than a comparable VFA. Steve110 07:20, 17 March 2007 (UTC)
I see some changes were made, but the main premise that CFB are higher bandwidth devices was not changed. This is simply wrong. The Bandwith of a CFA of comparable VOL is the same. The main difference to a VOA is the way these things are looked at. Steve110 22:24, 26 March 2007 (UTC)
According to Bruce Carter of the Advanced Linear Products division of Texas Instruments...
"The bandwidth specification given in op amp data sheets refers only to the point where the unit gain bandwidth of the device has been reduced by 3 dB by internal compensation and/or parasitics -- not very useful for determining the actual operating frequency range of the device."
"Internally compensated, voltage feedback amplifier bandwidth is dominated by an internal 'dominant pole' compensation capacitor, resulting in a constant gain/bandwidth limitation. Current-feedback amplifiers, in contrast, have no dominant pole capacitor and therefore can operate MUCH MORE CLOSELY TO THEIR MAXIMUM FREQUENCY AT HIGHER GAIN [emphasis added]. Stated another way, the gain/bandwidth dependence has been broken."
I believe the point Mr. Carter is making is that when you are using a gain significantly greater than 1, the CFA OP Amp has a significant advantage over the VFA Op Amp in terms of much greater frequency response.
Perhaps the article could be updated to reflect this? —Preceding unsigned comment added by 58.10.65.22 ( talk) 13:03, 11 January 2009 (UTC)
I believe the schematic diagram should show a resistor in parallel with Cs, as it is that internal resistor that determines the transimpedance gain of the I to V converter section. — Preceding unsigned comment added by 174.91.201.72 ( talk) 17:09, 1 September 2011 (UTC)
US3944906 "NORTON type current responsive operational amplifier" http://www.google.com/patents/US3944906 ? -- J. D. Redding 04:52, 28 August 2012 (UTC)
I came here to learn about the current-feedback architecture, so I'm not really qualified to make changes. But I believe that pink-outlined stage in the schematic should be called, simply, a voltage buffer. The triangle has a high impedance input and a low-impedance output whose voltage tracks the input, correct? That's not a "current amplifier", as stated in the graphic. Spiel496 ( talk) 18:51, 22 January 2021 (UTC)