Basic Principles of Electricity Chapter 1

Study Notes

Fundamentals of Electricity

Electric Charge (Q): Measured in coulombs (C), it represents the amount of electricity present in an object and is essential for electricity flow.
Current (I): The flow of electric charge through materials, measured in amperes (A).
Alternating Current (AC): A type of current that periodically changes direction, commonly found in household power outlets.
Direct Current (DC): A current that flows in a constant direction, such as that produced by batteries.
Source: The origin of electricity, including batteries and power stations, that supplies energy to a circuit.
Load: Devices that consume electricity from a circuit, e.g., light bulbs or motors.
Path: The route through which electricity flows, typically through connecting wires.
Electricity: The flow of charged particles (primarily electrons) that powers electronic devices.
Voltage (V): The electrical force driving current through a circuit, measured in volts (V), akin to pressure in a fluid.

Current Flow Principles

Current Flow: Results from a difference in electrical potential (voltage) between two points, pushing electric charges through a conductive path.

Ohm's Law Characteristics

Ohm’s Law Definition: Establishes the relationship between voltage (V), current (I), and resistance (R).
Current Proportionality: Current (I) is directly proportional to voltage (V) and inversely proportional to resistance (R).
Power Dependency: Power increases with the square of the current; even minor increases in current significantly affect power.
Heat Generation: Resistors convert electrical energy into heat based on current flow and their resistance level.

Operational Amplifiers (Op-Amps)

Definition: An electronic device designed to amplify weak electrical signals, with two input terminals and one output terminal.
Inputs: Comprises inverting (-) and non-inverting (+) terminals, with the output being the amplified difference between the inputs.
High Gain: Op-Amps possess very high gain, enhancing small input signals significantly.
Feedback Mechanism: Stabilizes gain and performance using feedback to achieve predictable results.
Power Supply Requirement: Necessitates an external power supply (both positive and negative voltages) for operation.

Types of Op-Amps

Non-inverting Voltage Amplifier:
- Input is applied to the non-inverting terminal (+).
- Output is in phase with the input and amplified.
- Gain formula: ( Av = 1 + \frac{Rf}{Ri} ).
Inverting Voltage Amplifier:
- Input is applied to the inverting terminal (−).
- Output is inverted and amplified.
- Gain formula: ( Av = -\frac{Rf}{Ri} ).
Inverting Current-to-Voltage Transducer:
- Converts input current to a corresponding output voltage, which is inverted.
- Gain formula: ( V_{out} = -I_{in} \cdot R_f ).
Non-inverting Voltage-to-Current Transducer:
- Converts input voltage to proportional output current, maintaining phase.
- Gain formula: ( I_{out} = \frac{V_{in}}{R_f} ).
Inverting Current Amplifier:
- Amplifies input current while inverting its phase.
- Gain formula: ( I_{out} = -A_i \cdot I_{in} ).
Summing Amplifiers:
- Combines multiple input voltages into one output voltage.
- Gain formula: ( V_{out} = -\left(\frac{Rf}{R1}V1 + \frac{Rf}{R2}V2 + \ldots\right) ).
Non-Inverting Summing Amplifier:
- Inputs are applied to the non-inverting terminal (+); the output is in phase.
- Gain formula: ( V_{out} = \left(1 + \frac{Rf}{R_{in}}\right)\left(\frac{V1}{R1} + \frac{V2}{R2} + \ldots\right) ).
Differential Amplifier:
- Amplifies the difference between two input voltages and rejects common signals.
- Gain formula: ( V_{out} = \frac{Rf}{R_{in}}(V_2 - V_1) ).
Op-Amp as Adder/Subtractor:
- Adder Configuration: Inputs to the inverting terminal for summing outputs.
- Subtractor Configuration: One input to inverting, one to non-inverting terminal, determining output difference.