27-11-2016, 01:31 PM
(This post was last modified: 27-11-2016, 01:35 PM by Murphyv310.)
Hi Chaps.
I've encountered many circuits and applications using "virtual earth" mostly discreet semiconductor and op amps. I have also come across this type of circuit as well and have raised the query before (not here though) I also have replicated the circuits and built them. The thing that happens is they often dont behave in the way a virtual earth circuit should.
The coupling and circuit design is no different to me than umpteen other designs, all the difference I see is the lack of a first stage cathode bypass cap that I understand and the feedback network from anode to grid of the second stage for RIAA equalisation. There is no DC path from the RC network to either anode or grid of stage 2 . The input of stage 2, in fact both stages are high impedance and not at zero impedance, if they were zero impedance then this would damp the output of the first stage.
Surely to get a "current" amplifier we need to be thinking of grounded Grid or Base in a transistor amp?
Sorry but I still don't get it
I've encountered many circuits and applications using "virtual earth" mostly discreet semiconductor and op amps. I have also come across this type of circuit as well and have raised the query before (not here though) I also have replicated the circuits and built them. The thing that happens is they often dont behave in the way a virtual earth circuit should.
The coupling and circuit design is no different to me than umpteen other designs, all the difference I see is the lack of a first stage cathode bypass cap that I understand and the feedback network from anode to grid of the second stage for RIAA equalisation. There is no DC path from the RC network to either anode or grid of stage 2 . The input of stage 2, in fact both stages are high impedance and not at zero impedance, if they were zero impedance then this would damp the output of the first stage.
Surely to get a "current" amplifier we need to be thinking of grounded Grid or Base in a transistor amp?
Sorry but I still don't get it
