The pole of a PMOS current mirror is an important parameter that determines its frequency response. A higher pole frequency results in a faster response time, while a lower pole frequency results in a slower response time. In this article, we will show you how to calculate the pole of a PMOS current mirror. We will also provide some tips on how to improve the frequency response of your current mirror.
The pole frequency of a PMOS current mirror is determined by the following equation:
$$f_p = \frac{1}{2\pi R_L C_L}$$
Where:
- $$f_p$$ is the pole frequency in Hz
- $$R_L$$ is the load resistance in ohms
- $$C_L$$ is the load capacitance in farads
In order to improve the frequency response of your current mirror, you can decrease the value of RL or CL. However, decreasing the value of RL will also decrease the output current of the current mirror. Similarly, decreasing the value of CL will also decrease the input capacitance of the current mirror. Therefore, you must carefully consider the trade-offs involved when choosing the values of RL and CL.
In addition to the above, there are a few other factors that can affect the frequency response of a PMOS current mirror. These factors include the transconductance of the PMOS transistors, the parasitic capacitances of the transistors, and the layout of the current mirror. By carefully considering all of these factors, you can design a current mirror with the desired frequency response.
Analytical Derivation of Pole Frequency
The pole frequency of a PMOS current mirror can be derived analytically using the small-signal model of the circuit. The transconductance of the PMOS transistor is given by:
$$g_m = \frac{I_D}{V_{GS}-V_{th}}$$
where $I_D$ is the drain current, $V_{GS}$ is the gate-source voltage, and $V_{th}$ is the threshold voltage.
The output resistance of the PMOS transistor is given by:
$$r_o = \frac{V_{DS}}{I_D}$$
where $V_{DS}$ is the drain-source voltage.
The pole frequency is given by:
$$f_p = \frac{1}{2\pi r_oC_L}$$
where $C_L$ is the load capacitance.
The following table summarizes the key equations used in the analytical derivation of the pole frequency:
| Equation | Description |
|---|---|
| $$g_m = \frac{I_D}{V_{GS}-V_{th}}$$ | Transconductance of the PMOS transistor |
| $$r_o = \frac{V_{DS}}{I_D}$$ | Output resistance of the PMOS transistor |
| $$f_p = \frac{1}{2\pi r_oC_L}$$ | Pole frequency |
How To Calculate Pole Of Pmos Curent Mirror
To calculate the pole of a PMOS current mirror, you need to know the following parameters:
- The transconductance of the PMOS transistor (gm)
- The output capacitance of the PMOS transistor (Cout)
- The load resistance (RL)
The pole frequency is given by the following equation:
“`
fp = gm / (2π * Cout * RL)
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For example, if the PMOS transistor has a transconductance of 10 mA/V, an output capacitance of 100 fF, and the load resistance is 10 kΩ, the pole frequency would be:
“`
fp = 10 mA/V / (2π * 100 fF * 10 kΩ) = 159 kHz
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People Also Ask About How To Calculate Pole Of Pmos Curent Mirror
What is the purpose of a current mirror?
A current mirror is an electronic circuit that copies a current from one place to another. It is often used to create a reference current or to amplify a current.
What are the different types of current mirrors?
There are two main types of current mirrors: the bipolar junction transistor (BJT) current mirror and the MOS field-effect transistor (MOSFET) current mirror.
What are the advantages of using a PMOS current mirror?
PMOS current mirrors offer several advantages over BJT current mirrors. They have a higher input impedance, a wider bandwidth, and a lower output impedance.
