JanniS
Newbie level 6
Hi!
I am doing a class AB common source output amplifier with a folded cascode gain stage. The load is 1pF and 10 kHz. supply is 0-5V. the gain is > 70 dB
Everything was working as expexted until I changed the DC voltage of the load.
When loads are grounded the phase and gain are as I expected, but as I turn up the common mode load voltage, the phase starts at -180 degrees at DC and at the dominant pole it goes up to -90 degrees as if it all of a sudden is a right half plane pole. It starts around 2.2V.
If I make transient analysis they are not unstable but the same as when loads are grounded.
I am not sure about what to do. i tried to sweep the load common mode and look at other voltages and currents, but nothing weird is going on except for the phase
- - - Updated - - -
I have a input common mode at 2.5 (half the supply) and negative feedback through a 10G Ohm resistor and 10 F capacitor in order to create a dc voltage at 2.5 at output node
I am doing a class AB common source output amplifier with a folded cascode gain stage. The load is 1pF and 10 kHz. supply is 0-5V. the gain is > 70 dB
Everything was working as expexted until I changed the DC voltage of the load.
When loads are grounded the phase and gain are as I expected, but as I turn up the common mode load voltage, the phase starts at -180 degrees at DC and at the dominant pole it goes up to -90 degrees as if it all of a sudden is a right half plane pole. It starts around 2.2V.
If I make transient analysis they are not unstable but the same as when loads are grounded.
I am not sure about what to do. i tried to sweep the load common mode and look at other voltages and currents, but nothing weird is going on except for the phase
- - - Updated - - -
I have a input common mode at 2.5 (half the supply) and negative feedback through a 10G Ohm resistor and 10 F capacitor in order to create a dc voltage at 2.5 at output node
