sjamil02
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Hi all,
I have designing folded cascode OTA as shown in the schematic. I can get reasonably good gain (74dB) and f-3dB=600kHz using 130nm (1.2V) process. What bothers me was the wide swing cascode current mirror of PM12 and NM16 (the circled transistor in the schematic) is in triode region. In the schematic I also display the operating point.
For PM12--> vdssat=98mV, vds=64mV
For NM16--> vdssat=80mV, vds=44mV.
Is this expected for a given current mirror topology? The transistor behaves like voltage controlled resistor in triode region, therefore small change of bias voltage will cause large variation in current. So clearly this is not what we want.
How to make those two transistors going more into saturation?
Thanks
sj
I have designing folded cascode OTA as shown in the schematic. I can get reasonably good gain (74dB) and f-3dB=600kHz using 130nm (1.2V) process. What bothers me was the wide swing cascode current mirror of PM12 and NM16 (the circled transistor in the schematic) is in triode region. In the schematic I also display the operating point.
For PM12--> vdssat=98mV, vds=64mV
For NM16--> vdssat=80mV, vds=44mV.
Is this expected for a given current mirror topology? The transistor behaves like voltage controlled resistor in triode region, therefore small change of bias voltage will cause large variation in current. So clearly this is not what we want.
How to make those two transistors going more into saturation?
Thanks
sj