AMP

Goal

Design and build an analog audio amplifier as part of a larger audio-mixing system. The amplifier uses two inverting stages to achieve adjustable amplification without reversing the final signal polarity.

Constraints

The documented amplifier design uses two op-amp stages, resistor networks and a 2 kΩ feedback potentiometer, with a split ±4.5 V supply specified for hardware. The broader project requirements included mixing two mono inputs, three frequency bands, battery and DC power, and electrical and thermal safety. These were system requirements, not all independently verified outcomes.

Process

As part of a three-person group project, I designed the entire circuit schematic myself. The amplifier section used two successive inverting stages, each with a nominal gain of -2, producing an overall nominal gain of +4. I used LTspice to simulate the circuit and document the input, intermediate and output waveforms, with a potentiometer in the feedback network for adjustable gain.

I also physically assembled the circuit and carried out unit testing. The surviving unit-test report documents simulation and hardware procedures using a function generator, oscilloscope and power supply; the separate acceptance-test report covers signal mixing, power supply, physical constraints and safety checks. My recollection confirms the physical build and tests, while the available reports do not provide a complete record of measured results or every acceptance criterion passing.

Result

Designed the complete schematic, built the hardware and performed unit testing within a three-person project. The surviving records include the schematic, LTspice waveforms and written unit and acceptance-test procedures. Detailed measurements and a definitive pass/fail result for every system requirement are no longer available.