Difference between revisions of "220-A3.3"
Jump to navigation
Jump to search
| Line 4: | Line 4: | ||
# Plot the frequency response of NMOS and PMOS transistors. | # Plot the frequency response of NMOS and PMOS transistors. | ||
| − | == MOS | + | == MOS Transition Frequency == |
[[File:MOS ss highfreq.png|thumb|400px|Figure 1: The MOS transistor small signal model.]] | [[File:MOS ss highfreq.png|thumb|400px|Figure 1: The MOS transistor small signal model.]] | ||
| + | At high frequencies, the MOS gate-to-source capacitance, <math>C_{GS}</math> and the gate-to-drain capacitance, <math>C_{GD}</math> limits the MOSFET current gain at high frequencies, and thus, needs to be included in the two-port model, as shown in Fig. 1. The short-circuit current gain can be expressed as: | ||
| + | |||
| + | {{NumBlk|::|<math>A_i=\frac{i_{\mathrm{out}}{i_{\mathrm{in}}=\frac{g_m}{j\omega\left(C_{GS}+C_{GD}\right)}</math>|{{EquationRef|1}}}} | ||
| + | |||
| + | We then define the transition frequency, <math>f_T</math> as the frequency when magnitude of the short-circuit current gain is equal to 1, or: | ||
| + | |||
| + | {{NumBlk|::|<math>\left|A_i\right|=\left|\frac{i_{\mathrm{out}}{i_{\mathrm{in}}\right|=\frac{g_m}{\omega_T\left(C_{GS}+C_{GD}\right)}=\frac{g_m}{2\pi f_T\left(C_{GS}+C_{GD}\right)}=1</math>|{{EquationRef|2}}}} | ||
| − | |||
{| | {| | ||
| [[File:NMOS ft corners.png|thumb|400px|Figure 2: The NMOS Transition Frequency.]] | | [[File:NMOS ft corners.png|thumb|400px|Figure 2: The NMOS Transition Frequency.]] | ||
Revision as of 22:53, 19 October 2020
Activity: MOS Frequency Response
- Instructions: This activity is structured as a tutorial with an activity at the end. Should you have any questions, clarifications, or issues, please contact your instructor as soon as possible.
- At the end of this activity, the student should be able to:
- Plot the frequency response of NMOS and PMOS transistors.
MOS Transition Frequency
At high frequencies, the MOS gate-to-source capacitance, and the gate-to-drain capacitance, limits the MOSFET current gain at high frequencies, and thus, needs to be included in the two-port model, as shown in Fig. 1. The short-circuit current gain can be expressed as:
-
(1)
-
We then define the transition frequency, as the frequency when magnitude of the short-circuit current gain is equal to 1, or:
-
(2)
-
