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I hope that my story about this amazing circuit of a source follower with dynamic load will increase your interest in more sophisticated analog circuits...

I hope that my story about this amazing circuit of a source follower with dynamic load will increase your interest in even more sophisticated analog circuits...

The input voltage is obtained by the potentiometer P connected between the supply rails. For simplicity, the case when VIN = 0 V (the wiper is in the middle) is shown. As a result of the voltage compensation, the output voltage is VOUT = VIN = 0 V. Let's see how this is obtained.

This technique is known as "voltage shifting". It is used for the first time by Widlar when designing 702 op-amp. Since the "shifting" voltage is "floating, it is created by passing constant current through a constant resistor. Thus its voltage drop stays constant when the input voltage varies.

The input voltage is obtained by the potentiometer P connected between the supply rails. For simplicity, the case when VIN = 0 V (the wiper is in the middle) is shown. As a result of the voltage compensation, the output voltage is VOUT = VIN = 0 V. Let's see how this is achieved.

This technique is known as "voltage shifting". It is used for the first time by Widlar when designing 702 op-amp. Since the "shifting" voltage is "floating, it is created by passing constant current through a constant resistor. Thus the voltage drop across the resistor stays constant when the input voltage varies.

Passive compensation. The idea of ​​this old technique is to compensate for a disturbance by an equivalent "anti-disturbance". It is not only a circuit idea; it can be seen all around us. In the specific OP's circuit this means to compensate for voltage by an "anti-voltage" - Fig. 2.

Fig. 2. The circuit operation visualized by voltage bars in red and current loops in green (a geometrical interpretation).

The input voltage is obtained by the potentiometer P connected between the supply rails. For simplicity, the case when VIN = 0 V (the wiper is in the middle) is shown. Accordingly, the output voltage is VOUT = VIN = 0 V.

Passive compensation. The idea of ​​this old technique is to compensate for a disturbance by an equivalent "anti-disturbance". It is not only a circuit idea; it can be seen all around us. In the specific OP's circuit this means to compensate for the voltage VGS by an "anti-voltage" -VGS (Fig. 2).

Fig. 2. The circuit operation is visualized by voltage bars in red and current loops in green (a geometrical interpretation).

The input voltage is obtained by the potentiometer P connected between the supply rails. For simplicity, the case when VIN = 0 V (the wiper is in the middle) is shown. As a result of the voltage compensation, the output voltage is VOUT = VIN = 0 V. Let's see how this is obtained.