RC Circuits: Resistors and Capacitors

Electronic Circuit Parameters

• Electronic devices include transistors, integrated circuits (ICs), and sensors
• These are used in electronic systems

Basic Circuits: Resistor-Capacitor (RC) Circuits

• RC circuits consist of resistors and capacitors
• They can be connected in series or parallel
• They are used for filtering, signal conditioning, and timing applications
• In low-pass filters, RC circuits allow low-frequency signals to pass while attenuating high frequencies
• In high-pass filters, they allow high-frequency signals to pass while blocking low frequencies
• Further applications are oscillators and time delay circuits
• Resistance (R) is opposition to current flow, measured in ohms (Ω)
• Capacitance (C) is the ability to store electrical charge, measured in farads (F)
• Time constant (τ = RC) determines charging and discharging speed of a capacitor
• Frequency response defines how the circuit behaves across different frequencies
• Voltage and current ratings are maximum allowable levels to prevent damage

Basic Circuits: Light Emitting Diode (LED) Driver Circuits

• An LED driver circuit regulates the power supplied to an LED and prevents damage due to excessive current, ensuring stable operation
• These circuits limit current using resistors or current sources
• They can include PWM control for brightness adjustment
• Common applications are indicator lights, display panels, and lighting systems
• Forward voltage (Vf) is the voltage drop across the LED when conducting
• Forward current (If) is the current required for proper LED operation
• Resistance (R) limits current to the LED
• Power dissipation is heat generated during operation

Basic Circuits: Charger Circuits

• Battery chargers regulate voltage and current to safely charge batteries
• This prevents overcharging or damaging them
• Linear or switch-mode power supplies are used for charging
• These chargers can include trickle, fast, and pulse charging methods
• Common applications include use for mobile devices, automotive batteries, and rechargeable tools
• Charging voltage (V) is the required voltage to charge the battery
• Charging current (A) determines charging speed
• Battery capacity (mAh or Ah) defines how much charge a battery can store
• Charge time is the duration needed for full charging

Basic Circuits: Voltage Divider Circuits

• A voltage divider circuit consists of resistors connected in series to divide a voltage into smaller fractions

Basic Circuits: Relay Driver Circuits

• A relay driver circuit controls the switching of a relay using a low-power transistor or MOSFET
• Circuits like this are used to interface microcontrollers with high-power loads
• Circuits like this provide electrical isolation between control and load circuits
• These are commonly found in automation and protection circuits
• Relay coil voltage and current are required values to activate the relay
• Transistor/MOSFET parameters (Vce, Ic, Rds(on)) define switching performance
• Base/gate drive voltage controls the switching mechanism
• Power dissipation determines heat generated during operation

Intermediate Circuits: A 555 Timer Circuit - Astable Multivibrator

• An astable multivibrator is a circuit that continuously switches between high and low states, generating a square wave
• These are used in LED blinkers, oscillators, and clock circuits
• Frequency is determined by resistor-capacitor values
• Frequency (f = 1.44 / (R1 + 2R2)C) determines oscillation speed
• Duty cycle is the ratio of high to low pulse duration
• Capacitor and resistor values control timing characteristics

Intermediate Circuits: A 555 Timer Circuit - Monostable Multivibrator

• A monostable multivibrator is a circuit that generates a single pulse output when triggered
• Circuits like this are used for pulse generation, timers, and delay circuits
• The pulse duration is determined by resistor-capacitor values
• Pulse width (T = 1.1RC) determines output pulse duration
• Trigger voltage activates the circuit

Intermediate Circuits: Operational Amplifier (Op-Amp) Circuit - Inverting and Non-Inverting Amplifiers

• Op-amp circuits amplify input signals with a specific gain
• An inverting amplifier provides negative gain
• A non-inverting amplifier provides positive gain
• Gain (A = -Rf/Rin for inverting, A = 1 + Rf/Rin for non-inverting) defines amplification factor
• Input impedance is the resistance seen at the input
• Output voltage range defines voltage swing limits

Intermediate Circuits: Pulse Width Modulation (PWM) Circuits

• PWM is a technique that modulates the width of pulses to control power delivery
• PWM is used in motor speed control, LED dimming, and power regulation
• This is common in microcontroller-based applications
• Duty cycle is the percentage of high-time in a pulse
• Frequency determines switching rate
• Voltage and current limits ensure safe operation

Advanced Circuits: Switch Mode Power Supply - Buck, Boost, and Buck-Boost Converters

• Buck, Boost, and Buck-Boost Converters are DC-DC converters that regulate voltage efficiently
• A buck converter reduces voltage
• A boost converter increases voltage
• A buck-boost converter can increase or decrease voltage
• Input and output voltage defines conversion range
• Switching frequency determines efficiency
• Efficiency is the ratio of output to input power

Control Circuits: PID Control Circuits

• A PID control system is a closed-loop control system and regulates processes
• Regulation is done with proportional, integral, and derivative components
• These are used in industrial automation, robotics, and motion control
• PID systems provide precise control over temperature, speed, and position
• Proportional gain (Kp) determines response strength
• Integral gain (Ki) corrects steady-state errors
• Derivative gain (Kd) predicts and corrects future errors
• Response time is time taken to reach stable operation