How are negative voltage values ​​obtained?

Question

Electronics

How to get minus - 4 volts?

Answer 1

"Zero" is a matter of choosing a reference point. For example, you have 2 3 volt batteries connected in series.
If you chose "zero" the negative pole, then you will have +6 volts.
If you chose "zero" the midpoint (where the batteries are connected), then you will have +3 volts and -3 volts (bipolar power supply)
If you chose the positive pole as zero, then you will have -6 volts.
The latter is rare, except in some very specific schemes. But a bipolar source with a "zero" at the midpoint is quite.

Answer 2

Elementary Watson. Here are three ways:
1. If the circuit has a source of negative voltage greater than 4 volts, power a three-pin stub from it (for example, LT3094 with a diode in the control leg) and get -4 V at the output.
2. If there is an AC voltage source with an output transformer, then do as shown here: But remove the upper diode with a capacitor (they are not needed for negative voltage).
3. If there is the same source, but without a transformer, then build a doubler, as shown here: There is also an extra detail here - one of the capacitors, C2 or C3.
I see you are not satisfied with my answer. But, as they say. What is asked is answered.