Design and production of audio preamplifiers ----- NE5532 pre-amplifier

Keywords: ne5532, front amplifier circuit diagram Author: Mao Ruili The main technical indicators of the preamplifier are as follows. Voltage magnification: 10 times: passband: 50Hz ~ 20kHz. The knowledge points that should be mastered in this project. Three-pole amplification principle, intensive, integration, common analysis and computational analysis and computational analysis of co-amplifier circuits and the characteristics of multi-stage amplifiers. The principle and application of integrated op amps. 1. Circuit design This project is designed and produced is most of a two-channel megaphone. Each channel includes two parts of the preamplifier and volume adjustment circuit. The front amplifier is implemented by integrated op amp, and volume control is implemented with a two-link. The circuit is shown below. Integrated amplifies NE5532. NE5532 is dual op amp, which belongs to high performance low noise op amp, which has better noise performance, excellent output driving capability and relatively high small signals and power bandwidth. The circuit is two in-phase input amplifying circuits, and the voltage amplification of the circuit is about 11 times by analysis, respectively corresponds to two channels. The 200K potentiometer in the figure is to ensure the same size of the two channels; the role of the double potentiometer is to adjust the size of the two channel output voltages, that is, the size of the two channel volumes; the effect of the regulator is guaranteed The voltage supplied from the power supply is 15V; the power supply capacitance is to eliminate the effect of ripple and high frequency noise, prevent self-excitation; input, the capacitance of the output is active. 2. When the circuit makes the welding circuit Note: (1) The two-unit potentiometer should not be fixed on the board, and should be fixed to the housing when assembled, as a knob that adjusts the volume. (2) In order to ensure the balance of the two channels, the feedback resistance of one of the amplifiers can be replaced with a 200KΩ potentiometer, and the two amplifier gain is equal to the value of the value of the potentiometer. 3. Circuit Debug Method (1) Two channel input inputs the same AC small signal (UI = 10mV, f = 1 kHz) to measure two output voltage, observe the range of output voltage variations; (2) Adjust 200KΩ potentiometer, so that two The output voltage is equal. (3) Change the input signal frequency and record the output voltage amplitude. Find the frequency value of 0_7 times the output voltage to the maximum voltage, and draw the amplitude frequency characteristic curve. 4. Problems and solutions to the debugging process (1) No output voltage: Whether the power supply is turned on; whether the regulator tube is reversed or the model is wrong; the input end has a signal. (2) The magnification is not correct: the feedback resistor and the inverse-phase resistance resistance value are incorrect.