A MOSFET has two inputs, a high impedance input( gate) and a low impedance input ( source ) , the problem is that people see the gate as the " input " , and that way of thinking doesn't help.
Lots of circuits have multiple inputs. Lots of people use them in open loop, without feedback.
Are you suggesting that the number of inputs determines whether there is feedback or not??
BTW Both of your circuits in post # 38 have feedback, the left one has local source feedback, the right one has drain-to-source feedback.
Assuming V4 and V2 are the independent sources (you show them as DC but I assume it represents the independent input).
Jan
Are you suggesting that the number of inputs determines whether there is feedback or not??
BTW Both of your circuits in post # 38 have feedback, the left one has local source feedback, the right one has drain-to-source feedback.
Assuming V4 and V2 are the independent sources (you show them as DC but I assume it represents the independent input).
Jan
Exactly, if the output load is connected to source , you will have a circuit with negative feedback, but if the load is connected to drain and the source is connected to ground the circuit doesn't have negative feedback as the output is now isolated from the input
Depletion MOSFET and a resistor can provide a stable voltage reference, or an Lt3090 current source and resistor as Jan demonstrated in his most recent T-Reg. I haven't measured whether this setup's noise is less or greater than a string of zeners or a gas VR tube.
When one is worried about noise on one of these redneck zener regulators (for tubes) the zener stack can be RC filtered before it hits the FET gate. Step response might suck, but that is usually a don’t care. The stages being fed are usually class A amplifiers. Screens in a power stage don’t care too much about noise at the zener diode level (mu is single digits) so it can be made more responsive.
