Junus2012
Advanced Member level 5
Hello,
Below is the normal wide swing mirror,
I have swept the value of Iin and kept the current in the diode biasing constant as normal as we do for biasing the mirror in operational ampliifer or other circuit it used. Monitoring the output current I see the output is mirror of the input current (with mirror raio set to one) for a certain range, then it start to saturate and not following the input current. The doide biasing current is 10 uA and the mirror stop working around current more than 60 uA.
This is not an ideal behavoural of the mirror where it should always work to copy the input current to the output, thus it will create an issue when it is used as mirror load in operational amplifier during slew rate where the current is becoming more specially with adaptive biasing current of the differential pair tail current
I found one solution to extend the range is by decreasing the diode W/L further, but this still limited and has other drawback on the output range since it increase the overdrive voltage of the output mirror transistor
Below is the normal wide swing mirror,
I have swept the value of Iin and kept the current in the diode biasing constant as normal as we do for biasing the mirror in operational ampliifer or other circuit it used. Monitoring the output current I see the output is mirror of the input current (with mirror raio set to one) for a certain range, then it start to saturate and not following the input current. The doide biasing current is 10 uA and the mirror stop working around current more than 60 uA.
This is not an ideal behavoural of the mirror where it should always work to copy the input current to the output, thus it will create an issue when it is used as mirror load in operational amplifier during slew rate where the current is becoming more specially with adaptive biasing current of the differential pair tail current
I found one solution to extend the range is by decreasing the diode W/L further, but this still limited and has other drawback on the output range since it increase the overdrive voltage of the output mirror transistor