I am designing folded cascode amplifier by using current biasing method. However, the current flow into the cascode network is not stable. For example, I fixed the current 100uA. In the network, the current keeps reduced as I need to get the required voltage.
Dear Norhamizah,
After inspecting your circuit, i found that the transitors in the bottom figure are numbered differently from the top figure.
However, the transistors M15, M14 and M13 builds a current mirrors. you have to adjust the W/L ratio of the transistors. If the back gate is connected to the source for M14 and M13, you have to make W/L for M14 and m13 = 1/10 of W/L of M15.
If you have to connect the back gate to the main ground of the circuit and not the source of he transistors, W/L will be slightly different from the above case. You can get the exact value by experimentation.
wish you success
Norhamizah,
Would you please display your circuit such that one can analyse and trouble shout it?
Professor,
Thank you for your response. As shown in the 2nd attachment, the fixed current is 100uA (at M15). But the current flow through M14 and M13 only 1uA. The same situation happens to the rest cascode network.
Dear Norhamizah,
Here are links and attached files in subject.
-Biasing Calculations : Bipolar Junction Transistors ... - All About Circuits
www.allaboutcircuits.com/...4/biasing-calculations/
-Patent US7023281 - Stably-biased cascode networks - Google Patente
https://www.google.ch/patents/US7023281
-Brevet US5963096 - Amplifier circuit - Google Brevets
https://www.google.fr/patents/US5963096
-Chapter 9: Single Transistor Amplifier Stages: [Analog Devices Wiki]
https://wiki.analog.com/university/courses/.../chapter-...
Best regards
Dear Norhamizah,
After inspecting your circuit, i found that the transitors in the bottom figure are numbered differently from the top figure.
However, the transistors M15, M14 and M13 builds a current mirrors. you have to adjust the W/L ratio of the transistors. If the back gate is connected to the source for M14 and M13, you have to make W/L for M14 and m13 = 1/10 of W/L of M15.
If you have to connect the back gate to the main ground of the circuit and not the source of he transistors, W/L will be slightly different from the above case. You can get the exact value by experimentation.
wish you success
Dear Professors,
Thank you for your responses. I appreciated them very much. I am working on what you have explained/given above.
Have a nice day. :)
Regards.
dear horhamizah
hope this informations will cope your research out
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