#ee40m

[cat-notes-blog]

Transistors

Transistors are 3 terminal devices, with a source, gate, and drain. Current goes in the source and out the drain. 

pMOS should connect Vdd (at source) to lower voltages (at drain). They turn on if gate is connected to ground and off if gate is connected to Vdd. 

nMOS should connect ground (at source) to higher voltages. They turn on if the gate is connected to Vdd and off if the gate is connected to ground. 

Apparently there are two types of transistors: BJT (bi-polar junction) and MOFSET (metal oxide field effect). In class we used MOFSETs, but the tutorial at sparkfun goes over BJT. 

So the bi-polar junction transistor (BJT) has three pins: collector, base, emitter. Transistors are like two diodes with their cathodes (anodes) tied together. But that isn't how they actually work. 

Transistors = three different semi-conductor layers stacked together. 

n-type semi-conductors have extra electrons (they're "doped", and negative). 

p-type semi-conductors have electrons removed. They're positive. 

Basically we have Collector-Base-Emitter, each being a layer. NPN is when the Collector and Emitter are n-type and the base is p-type. PNP is the other way around. 

References:

https://learn.sparkfun.com/tutorials/transistors

[cat-notes-blog]

RC Circuits

There are three types of RC Circuits

1. RC Charging Circuit

An RC Charging Circuit is a capacitor and a resistor connected across a DC power supply. V + end connected to C + end. 

Time Constant: the time taken to charge / discharge a capacitor within a certain % of its max supply value. 

If resistor is connected in series with a capacitor forming an RC circuit, the capacitor charges over a time called transient response. Equal to about 5 time constants, 5 tau. 

Initially when the capacitor is completely discharged, it's the same as a short circuit. 

63% is one time constant. 

When the two voltages are equal, the capacitor acts like an open circuit. 

2. RC Discharging Circuit

A charged capacitor in series with a resistor. 

http://www.electronics-tutorials.ws/rc/rc_2.html

3. RC Waveforms

RC Integrator: low-pass filter that converts a square wave input into a triangular waveform output. 

RC Differentiator: high-pass filter that converts a square wave input into high frequency spikes at its output. 

[cat-notes-blog]

Capacitors and Inductors in Circuits

Capacitors in Parallel have the same voltage, and the total capacitance is the sum of all capacitances.

Capacitors in Series have the same current. Their capacitance is the inverse of the sum of all inverse capacitances. Opposite of resistors. 

Inductors in Parallel have the same voltage, and the total inductance is the inverse sum of all the inverse inductances. 

Inductors in Series have the same current, and the total inductance is the sum of the inductances.