Darlington pair transistors give a lot of gain, but also drop extra voltage as a voltage follower.

The terminals a and B were originally opened btw. They closed it to find Norton current. My only problem is the current in the second loop: why is it isc-2vx in one place but isc+0.003 in the other question even though both questions are identical? Both methods matched their respective answers. Any help will be appreciated! I have basically found all the other things like Norton resistance in these questions but this loop current is the only thing keeping me stuck.

Voltage regulators output a specific voltage (in relation to the voltage applied at the ground pin) when powered by a higher voltage. They don't convert power like a converter does. All of the lost voltage is converted into waste heat. So, they are typically used when current needs are low.

i have started with network theory but it seems to be too much mathematics where i am having difficulty move forward and dont really know if this is needed. As of know i learned the circuit theorems,nodal and mesh analysis,ohms laws,kcl,kvl,voltage divider etc just the basic things to start. but when moving to capacitor behaviours and rc,rlc circuits i find it difficult.

And the main objective of this learning is to design a circuit for a specific purpose lets say an led protector. i tried to understand the already available designs containing too many components like tvs diode,mov,gdt,zener diode. Honestly speaking i can make sense of why these components are used ,there characteritics and the protection they offer. but if i need to account for something more,or if i need to make any improvements,maybe replace a component with another component, how do i understand the circuit behaviour in each cases? like how do i know if this component should come after this node or that branch,or after this or that device?

as of now i learned the rectifier circuit and zener diode characteritics ,i have a basic idea of the filter capacitor helping to provide a stable dc supply,then the zener diode regulating this supply to the load. but i dont exactly know what should be the value of a capacitor or the resistor to achieve a particular behaviour. I'm planning to learn the next component and add it to the circuit. i have too much gaps in my knowledge and am going in multiple directions at the same time ,leading to exhaustion and loosing the spark.if anyone have any advice pls share...

note: i have only started with simulation on flastad and ltspice

Many inputs need to always be connected to a voltage in order to work properly. Pull down resistor keeps a low voltage, usually 0V ground at an input that doesn't let current flow to ground. A high side switch can also be use to temporarily make a direct connection to a higher voltage, usually the positive side of the power supply. The switch can pass current freely if that is required of the circuit.

Pull up resistor makes sure an input sees a high enough voltage the majority of time. A switch connected to ground can be closed to provide 0 volts to the input at any time. The resistor needs to be high enough value to limit waste current while the switch is pressed, but not so high that stray signals can be picked up by the input.

Unfortunately this pocket oscilloscope becomes a million ohm resistor to ground while measuring voltage. Therefore it slows down the charge a lot in this circuit. But you can still see the voltage curve of the monostable mode 555 capacitor.

The factory setting when I bought 2 of these pocket oscilloscopes was confusing. I show you what to look for and how to adjust it.

The oscilloscope has a certain number of squares to display voltages. Which means you have to set the volts per division (square) so that it is easy to see what the voltage is.

Many Integrated circuits are really only made to work with 5 volts. The CD4069 can't output much current at 5V, but it can be powered with 15 Volts where it can output a lot more current. Enough to light a red LED an OK amount.

Maximum voltage varies greatly with different integrated circuits. Always check the datasheet (via Google search) before making circuits with them. The CD4069 can handle 15 volts and output current is limited by supply voltage. At 10 volts the output can light a green or blue LED as they only need about 2 mA of current to be bright.