FPGA is a bit tired recently, I will open a pit of analog circuit design for everyone, it contains dry goods, please rest assured to eat
1. The overall design plan
2. Unit circuit design and principle description
2.1 Square wave generating circuit The
waveform generating circuit can be realized by the integrated operational amplifier chip constituting the arithmetic circuit.
The square wave generating circuit in the first step can be composed of hysteresis comparator and RC circuit, as shown in the figure
Designed with a general-purpose operational amplifier LM324 chip, C1 and R1 form an RC circuit, and R2, R3 and LM324 form a hysteresis comparator. The function of D1 and D2 is to stabilize the voltage.
The circuit waveform is as follows
2.2 Triangular wave generating circuit The
triangular wave generator uses an integrated operational amplifier to form an integrator, and then performs calculations on the square wave signal, as shown in the figure
The values of R4 and C2 must be calculated, otherwise the output waveform will be distorted
The waveform is shown in the figure
2.3 Sine wave generating circuit
Expands triangular wave signal by Fourier transform
It can be seen that when the frequency of the triangular wave is fixed or the change is small (changes within 3 times), a sine wave can be obtained through a low-pass filter. The filter frequency should be greater than the fundamental frequency and less than the third harmonic component frequency.
The circuit diagram is as follows
The waveform at 50hz triangle wave is as follows
Third, the selection of components and related data and parameters The
core chip integrated op amp chooses the LM324 general purpose op amp
Fourth, the overall circuit schematic diagram and working principle description The
overall circuit is as follows
From left to right are the square wave generating part, the triangular wave generating part, and the sine wave generating part.
The square wave generating part is composed of a hysteresis comparator composed of LM324 and an RC circuit; the triangular wave generating part is an integral operation circuit composed of LM324; the sine wave generating part is a low-pass filter composed of LM324.
The principle of square wave generation is that the RC circuit waveform outputs a square wave under the choice of the hysteresis comparator; the principle of triangular wave generation is that the square wave is integrated to obtain a triangular wave; the principle of sine wave generation is because according to the Fourier transform, the triangular wave can be transformed into The sum of sine waves, so it is easy to get a sine wave through a low-pass filter. The frequency of the filter should be greater than the fundamental frequency and less than the frequency of the third harmonic component.
The three final waveforms
If there is any error, please point it out, thank you for watching!