nakulnarang
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I am new to analog design and currently working on the attached circuit. I have some doubts on the working of the circuit as well as deciding the width of certain transistors.
Max Area - 330 by 65
1. How to calculate the THD of the circuit theoretically and how does values of R2a, R2b affects the value of THD.
2. What is the advantage of adding R1 in the input stage? On running few simulations, i noticed that on increasing the value of R1, thd increasing thus improving the linearity of the circuit.. But I am not able to understand why?
3. Also R1 affects the bandwidth of the circuit i.e. increasing R1 decreases the bandwidth. As per my understanding, for a folded cascod structure, the unity gain bandwidth directly depends on gm(input)/CL but not able to understand how adding R1 affects the UGBW?
4. How do I analyse the settling time of the circuit?
5. How do I decided the width and length of the Long channel transistor and the rest of the transistors in the startup of the biasing circuit.
M36 , M37, M38 and M39 - long channel.
6. Why do I need CMFB circuit? As per my understanding, the since we use Pmos and Nmos current sources, the process variations and the temperature would affect the output voltage at load cap and thus to stablize the output voltage we use CMFB. What I am not able to understand is that on removing the CMFB circuit, M7 to M10 enter triode. Can some please explain why??
Thanks for your help
Max Area - 330 by 65
1. How to calculate the THD of the circuit theoretically and how does values of R2a, R2b affects the value of THD.
2. What is the advantage of adding R1 in the input stage? On running few simulations, i noticed that on increasing the value of R1, thd increasing thus improving the linearity of the circuit.. But I am not able to understand why?
3. Also R1 affects the bandwidth of the circuit i.e. increasing R1 decreases the bandwidth. As per my understanding, for a folded cascod structure, the unity gain bandwidth directly depends on gm(input)/CL but not able to understand how adding R1 affects the UGBW?
4. How do I analyse the settling time of the circuit?
5. How do I decided the width and length of the Long channel transistor and the rest of the transistors in the startup of the biasing circuit.
M36 , M37, M38 and M39 - long channel.
6. Why do I need CMFB circuit? As per my understanding, the since we use Pmos and Nmos current sources, the process variations and the temperature would affect the output voltage at load cap and thus to stablize the output voltage we use CMFB. What I am not able to understand is that on removing the CMFB circuit, M7 to M10 enter triode. Can some please explain why??
Thanks for your help
