feedback and feedthrough capacitance

[padoh]

what is the difference between feedthrough and feedback capacitor? what is the meaning of this statement "CGD represents miller capacitance feedback while CDG represents miller capacitance feedback"

 

[jiripolivka]

what is the difference between feedthrough and feedback capacitor? what is the meaning of this statement "CGD represents miller capacitance feedback while CDG represents miller capacitance feedback"

There are quite substantial differences!

1. A"feedthrough" capacitor is used to pass DC Current through a metal wall while its capacitance (and sometimes a ferrite bead added) suppresses the AC components on the line. Usually the higher the AC frequency, the higher AC signal attenuation.

2. A feedback capacitor is connected usually between an amplifier input (in case of opamps the inverting input) and output. Such connection due to amplifier gain changes the amplifier into a low-pass filter. Filter parameters are adjusted by the feedback capacitance, feedback resistor and the series resistor from a signal source to amplifier input.

3. "Miller" capacitance was originally the one existing between the control grid and plate of a vacuum triode. Today it is the capacitance between amplifier inverting input and output, often including parasitic components of a circuit.

 

[padoh]

what is the meaning of this statement "CGD represents miller capacitance feedback while CDG represents miller capacitance feedthrough"..apparently it seems both capacitances exist between the input and output termainals of an amplifier?? is that true?

 

[jiripolivka]

what is the meaning of this statement "CGD represents miller capacitance feedback while CDG represents miller capacitance feedthrough"..apparently it seems both capacitances exist between the input and output termainals of an amplifier?? is that true?

In this context I think both expressions are equal. English allows similar synonyming to occur.