This Dev Log is pulled straight from my notes

Goals

- Understand the difference between N and P channel MOSFETs
- Understand NPN transistors
- finalize components needed in the circuit

N channel vs P Channel Mosfet
- N-Channel MOSFET is triggered by applying a **Positive** voltage to the gate relative to the source
- Used when switching load side
- P-Channel MOSFET is triggered by applying a **Negative** voltage to the gate relative to the source
- Used when switching ground side

NPN Transistor
- type of BJT (Bipolar Junction Transistor)
- commonly used for amplification or switching
- Pins
- Collector 
- Positive end of the transistor
- Connected to the high voltage potential or positive supply
- when transistor is turned on current flows from collector to emitter
- Usually connected to the load
- Base 
- control terminal of the transistor
- current flowing into the base controls the current flow from collector to emitter
- Relationship between base and collector current is determined by the transistor gain (hFE)
- Emitter
- Negative terminal of the transistor
- connected to negative side or ground
- current flows from collector to emitter when transistor is turned on
- When enough positive voltage is applied to the base current flows from collector to emitter the amount of current that flows is proportional to the amount of current flowing into the base and is tied to the transistor gain.
- Collector-Emitter junction is normally **Reverse-biased** meaning that the collector voltage is higher than the emitter voltage. This acts as an open switch preventing current from flowing from collector to emitter

Datasheet Values to Look for

- Collector-Emitter Voltage (VCEO): maximum voltage that can be applied between collector and emitter when the base is open
- Collector-Base Voltage (VCBO): Maximum voltage that can be applied between the collector and the base when the emitter is open
- Emitter-Base Voltage (VEBO): maximum voltage that can be applied between the emitter and the base when the collector is open
- Collector Current (IC): Maximum continuous Current that can flow through the transistor from collector to emitter
- Leakage Current (ICEO): Current that flows from Collector to emitter when the transistor is off
- Power Dissipation (PD): Max power the transistor can dissipate without damage
- Current Gain (hFE): ratio of collector current to base current
- How much can the transistor amplify current going into the base pin
- Transition Frequency (fT): Frequency that the transistor can switch on and off
- Collector-Emitter Saturation Voltage (VCE(sat)): the minimum voltage drop from collector and emitter when the transistor is properly saturated.
- Base-Emitter On-Voltage(VBE(on)): minimum voltage required between base and emitter to turn the transistor on
- Collector-Emitter Breakdown Voltage (BVCEO): Voltage at which the reverse-biased collector-emitter junction fails

Voltage Divider
- Uses 2 Resistors to divide a larger voltage into a smaller one
- Used to created a reference voltage
- simple Schematic
Vin ---+
       |
       R1
       |
Vout --+
       |
       R2
       |
GND ---+
- the output voltage is determined by the ratio of the resistance of R1 and R2 according to the formula
- Vout = Vin x (R2/ (R1+R2))
- Vin is the input voltage
- Vout is the output voltage between the 2 resistors
- You can get any voltage between Vin and V0
- Limited when it comes to supplying current to a load
- Used only in high impedance loads or other circuits that draw minimal current