A collection of typical MCU essay competition questions (Part 2)

Microcontroller Paper III Practical Low Frequency Power Amplifier

1. Mission

Design and manufacture a low-frequency power amplifier with weak signal amplification capability. The schematic diagram is as follows:

II. Requirements

1. Basic requirements

(1) When the sinusoidal signal input voltage amplitude of the amplifier channel is (5~700) mV and the equivalent load resistance RL is 8Ω, the amplifier channel should meet the following requirements:

① Rated output power POR ≥ 10W;

② Bandwidth BW ≥ (50～10000) Hz;

③ The nonlinear distortion coefficient under POR and within BW is ≤3%;

④ Efficiency at POR ≥ 55%;

⑤ When the input terminal of the preamplifier stage is short-circuited to ground, the AC sound power on RL=8Ω is ≤10mW.

(2) Design and manufacture a voltage-stabilized power supply that meets the requirements of this design task.

2. Development part

(1) Amplifier time response

① Square wave generation: The external sinusoidal signal source generates positive and negative symmetrical square waves through the conversion circuit: the frequency is 1000Hz, the rise time is ≤ 1μs, and the peak-to-peak voltage is 200mVpp.

When the above square wave is used to excite the amplifier channel, under RL=8Ω, the amplifier channel should meet the following requirements:

② Rated output power POR ≥ 10W; bandwidth BW ≥ (50 ~ 10000) Hz;

③ Under POR, the output waveform rise time and fall time are ≤12μs;

④ Under POR, the top slope of the output waveform drops ≤2%;

⑤ Under POR, the output waveform overshoot is ≤5%.

(2) Improvement of the performance indicators of the amplification channel and expansion of practical functions (such as improving efficiency, reducing nonlinear distortion, etc.).

3. Rating opinions

project

Score

Basic Requirements

Design and summary report: scheme design and demonstration, theoretical calculation and analysis, circuit diagram, test method and data, result analysis

50

Actual production completion status

50

Play part

Complete the first task

20

Complete the second item

10

Features and Innovation

Single chip microcomputer paper 4 design and production of practical signal source

1. Mission

Under the given ±15V power supply voltage condition, design and make a sine wave and pulse wave signal source.

II. Requirements

1. Basic requirements

(1) Sine wave signal source

① Signal frequency: 20Hz～20kHz step adjustment, step length is 5Hz

② Frequency stability: better than 10-4

③ Non-linear distortion coefficient ≤ 3%

(2) Pulse wave signal source

① Signal frequency: 20Hz～20kHz step adjustment, step length is 5Hz

② Rise time and fall time: ≤1μs

③ Flat top slope drop: ≤5%

④ Pulse duty cycle: 2%~98% adjustable in steps of 2%

(3) Common requirements for the above two signal sources

① Frequency can be preset.

② When the load is 600Ω, the output amplitude is 3V.

③ Complete the 5-digit digital display of frequency.

2. Development part

(1) The frequency step size of sine wave and pulse wave is changed to 1Hz.

(2) The amplitude of the sine wave and pulse wave can be adjusted in steps, with an adjustment range of 100mV to 3V and a step length of 100mV.

(3) The frequency of sine wave and pulse wave can be stepped automatically with a step size of 1Hz.

(4) Reduce the nonlinear distortion coefficient of the sine wave.

3. Scoring Criteria

Basic requirements for project scoring Design and summary report: scheme design and demonstration, theoretical calculation and analysis, circuit diagram, test method and data, result analysis 50 Actual production completion 50 Partial completion of the first item 10 Complete the second item 10 Complete the third item 5 Complete the fourth item 5 Features and innovation 20