What Is a Function Generator?
The function generator is a multi-waveform signal source. It can generate sine, square, triangle, sawtooth, and even arbitrary waveforms. Some function generators also have modulation functions, which can perform amplitude modulation, frequency modulation, phase modulation, pulse width modulation and VCO control.
Function generator
- Function generator is a multi-waveform
- The function generator has a wide frequency range and a wide range of uses. It is an indispensable general-purpose signal source. It can be used in production testing, instrument maintenance and laboratories.
- Designing a function generator to generate square waves,
- Frequency range: 10Hz ~ 100Hz, 100Hz ~ 1000Hz, 1kHz ~ 10kHz
- Frequency control method by changing RC
- (1) Design the principle according to the technical indicators and laboratory conditions
- (1) Option 1:
- From the design process of the circuit, the circuit is divided into three parts: sine wave part square wave part
- (1) Solder the circuit board according to the circuit diagram of scheme 1.
- (2) Before debugging, connect the circuit board to a voltage of ± 12 volts, and the ground wire is connected to the public ground wire at the power source.
Function generator frequency range
- To facilitate the measurement, connect the square wave signal on the circuit board to the oscilloscope, and close the switch of C1 = 10 & micro; F, disconnect the switch of C2 = 1uF, and then adjust RP2, and measure the change of the square wave signal frequency range;
- Turn off the switch of C1, close the switch of C2, adjust RP2 in the same way and record the range of the square wave signal frequency.The results are as follows:
|
|
|
|
|
|
- The above frequencies do not fully reach the required index range. After analysis, the reasons are:
- Through comparison, it is found that the overall frequency range is shifted down. There may be two reasons here. The first is the wear on the feedback channel, which makes the resistance value less than the calculated value. The second is the same problem with the resistance on the opposite side of the triangle wave amplifier.
Function generator output voltage
- Square wave:
- The wave signal above the circuit board is connected to the oscilloscope, and the RP1 is adjusted to measure the square wave peak-to-peak Vpp = 14V. It can be seen that the obtained value is consistent with the performance index.
- Triangle wave:
- Remove the square wave signal and access the triangle wave signal, adjust RP1, and measure the peak value of the triangle wave Upp = 5V can also meet the requirements of the subject.
- Sine wave:
- Connect the sine wave signal to the oscilloscope, adjust RP3 and RP4, and measure the sine wave peak-to-peak value Upp = 2.8V. It can also basically meet the project requirements.
- 3. Measurement of waveform characteristics:
- Rise time of square wave:
- Connect the square wave signal on the circuit board to the oscilloscope, and adjust the period adjustment knob on the oscilloscope until you can clearly observe the jump at the rising edge of the square wave signal. The measured square wave rise time is:
- tr = 6.4 & micro; s
- Analysis: The rise time does not meet the requirements. This can be solved by changing the op amp type. Change the rise time of the op amp by changing its speed.
- Triangular wave non-linear distortion:
- Remove the square wave signal and connect the triangle wave signal on the circuit board to channel 1 of the oscilloscope.The measured triangle wave signal parameters at this time are as follows:
- Frequency: f = 98.42Hz
- Peak-to-peak: Upp = 5V
- At this time, the triangle wave generated by the function generator on the experimental bench is used as the standard signal to connect to channel 2 of the oscilloscope, and its frequency and peak-to-peak value are adjusted to be consistent with the triangle wave signal parameters to be tested (f = 98.42Hz, Upp = 5V) .
- Compared with the dual trace mode on the oscilloscope, it is found that the triangle waves of the two channels are completely coincident, indicating that there is no non-linear distortion.
- Sine wave is seriously distorted:
- Analysis: One pin of the sliding rheostat that adjusted the balance was broken. I took a wire to connect it, which caused the circuit to be misaligned and caused the static operating point to deviate from the original position. This led to this result. .