Tag: PMOS Gyrator

Gyrator

A simple PMOS gyrator for driver stage anode load

 This is a very simple PMOS based gyrator with only one transistor. You can use a Zetex ZVP0545a which is easy to obtain around here and is not a surface mount type (in case you don’t feel confident in working with SMD components).
Steps to complete the design on this gyrator are as follows:

  1. First you need to ensure you can bias correctly the Mosfet. Knowing your anode quiescent current (Ia) you can set R4 to ensure bias is stabilised as shown in the diagram (point 1)
  2. You then have to ensure you keep the MOSFET Vds at least 25V to 50V to ensure output capacitance is minimised and expected frequency response performance is achieved. Then R1 can be calculated as well knowing your target anode voltage (Va).  (point 2)
  3. R2 and R3 will set the anode voltage (Va) which is a design parameter in the gyrator, right?. And also you know the gate voltage (Vg) based on R4 and Vgs (i.e. +B-VR4-Vgs). You can calculate this resistor divider given these two definitions. Also R2 plays with the capacitor to define the rolloff frequency of your gyrator.