Small-Signal Audio Amplifier
A small-signal audio amplifier built and tested on breadboard, focused on analog circuit assembly, component selection, gain staging, and validating the signal path on real hardware.
Audio Amplifier
A site-native project entry using the existing photo and report already in the website files.
Project 1
Touchless Gesture-Controlled Light Switch
A contactless light switch activated by hand gesture or clap, designed to reduce wear and physical contact in shared spaces while running as a self-contained 9V battery-powered unit.
What
- Contactless light switching through gesture or clap input.
- Self-contained system with no bench supply required.
- Built around real sensor modules and relay control.
How
- Sharp GP2Y0D810Z0F IR sensor with 2-10 cm detection.
- MAX9814 microphone module for clap activation.
- ATmega328P C++ firmware for debounce, timing, and relay control.
- AZ34063U buck converter PCB stepping 9V down to 5V.
Result
- 60% false trigger reduction through filtering and reset timing.
- 3-9.5 cm adjustable detection range using a trimpot.
- ERC/DRC clean KiCAD PCB with BOM generated.
Project 2
Negative rail generation
LM741 Negative Power Supply
An inverting buck-boost converter that generates a stable -5V rail from a single positive supply, enabling dual-rail LM741 op-amp operation without an external signal generator.
What
- Generate a stable negative rail from a positive DC input.
- Support LM741 dual-rail operation under load.
- Minimise ripple while keeping the build self-contained.
How
- 1 mH inductor, N-MOSFET, 1N4148 diode, and 2200 uF output capacitor.
- 555 timer clock at approximately 25 kHz for PWM switching.
- Full LTSpice transient simulation before breadboard testing.
Result
- -5.0V stable output under 50 mA load.
- Output ripple below 320 mV.
- Powered LM741 amplifier produced a 6.3V peak-to-peak sine wave.
Project 3
LP / HP / BP outputs
Analog Filtering Circuit
A single-input, three-output active filter producing low-pass, high-pass, and band-pass outputs simultaneously from a +/-12V supply.
What
- LP, HP, and BP active filter outputs from one input.
- 1.2 kHz target cutoff frequency.
- Four simultaneous hard specifications to satisfy.
How
- Second-order active LP/HP topology for 40 dB/decade rolloff.
- MFB bandpass topology with independent frequency, Q, and gain control.
- Unity-gain buffers on outputs for output impedance at or below 1 kOhm.
Result
- 1.2 kHz cutoff confirmed on oscilloscope.
- Greater than 40 dB/decade rolloff against a 35 dB spec.
- +/-1.5 dB passband ripple and ERC/DRC clean PCB.
Project 4
G = 10-100
Current Measurement Amplifier
A current-to-voltage amplifier with continuous variable gain from 10 to 100, designed for high-side or low-side measurement without rewiring.
What
- Current-to-voltage amplifier for measurement applications.
- Continuous gain control from 10 to 100.
- Flat response target across 100 Hz to 10 kHz.
How
- 0.1 Ohm shunt with 100 mV drop at 1A full scale.
- 3-op-amp instrumentation amplifier rejects common-mode voltage.
- Single trimpot adjusts gain; output buffer uses 1 kOhm series resistor.
Result
- Gain adjustable from 10 to 100 with no component swap.
- +/-3 dB response from 100 Hz to above 10 kHz.
- High-side and low-side configurations validated.
Project 5
1V to 4V control
Voltage-Controlled Oscillator
A VCO mapping 1V to 1 kHz and 4V to 10 kHz, with dual triangle and square wave outputs inside a 0-5V rail.
What
- Linear control-voltage-to-frequency mapping.
- Triangle wave and square wave outputs.
- Output constrained to the 0-5V supply rail.
How
- Integrator op-amp and capacitor create linear ramp.
- Schmitt trigger comparator hysteresis defines thresholds.
- NMOS discharges the integrator capacitor at each threshold crossing.
Result
- 1-10 kHz output range met specification.
- Linear monotonic mapping confirmed from 1V to 4V.
- Both waveforms stayed within supply rail with stable operation.
Project 6
RPE / RISO / ILEAK
Electrical Test & Tag
Portable Appliance Testing using a Seaward PAC3760 DL, applying AS/NZS 3760:2022 safety checks to in-service equipment across residential and commercial sites.
What
- Visual inspection, earth bond, insulation resistance, and leakage current tests.
- Systematic electrical safety inspection of in-service equipment.
- Specification-driven pass/fail validation.
How
- RPE earth resistance verifies chassis-to-earth continuity.
- RISO applies 500 V DC to check insulation integrity.
- ILEAK measures leakage current under normal operating voltage.
Result
- AS/NZS 3760:2022 compliant test and tag records produced.
- Unsafe appliances identified and quarantined before re-energisation.
- Test registers and tag records maintained for audit readiness.
Technical Skills
Tools and methods used across the portfolio, grouped the same way as the original project document.
Hardware Design
- Analog circuit design
- Op-amp topologies: LM741, LM324
- Active filter design: LP, HP, BP
- Instrumentation amplifiers
- DC-DC power converters
PCB Design
- KiCAD schematic capture and ERC
- PCB layout and DRC
- 2-layer FR-4 boards
- Ground pour strategy
- Gerber export and BOMs
Simulation
- LTSpice transient, AC, and parametric simulation
- MATLAB and Simulink
- ADS: Advanced Design System
- Simulation-first methodology
Embedded & FPGA
- C/C++ on ATmega328P
- ADC, PWM, GPIO, interrupts
- Sensor interfacing
- Verilog, SystemVerilog, VHDL
- Vivado and Quartus
Programming
- C, C++, Python, MATLAB
- MIPS Assembly
- Git version control
- Shell scripting
Field & Test
- LV electrical installation
- Solar and inverter commissioning
- Oscilloscope, bench PSU, DMM
- AS/NZS wiring standards