2000H Square Wave Output I need 2000HZ square wave; commonly used electronic original How to lap the circuit to make it Thanks!

The following answers are from other Baidu users, I hope to help you:

A dual op-amp can be, such as the LM358;

One op-amp constitutes the oscillator circuit, generating a 2KHz square wave signal;

One op-amp constitutes the integrator circuit, which integrates the input square wave and outputs the triangular wave;

Signal generator is generally differentiated into function generator and arbitrary waveform generator, while function generator is designed to distinguish between function generator and arbitrary waveform generator. Signal generators are generally distinguished as function generators and arbitrary waveform generators, and function waveform generators in the design of analog and digital synthesis. As we all know, the digital synthesis function signal source on the frequency, amplitude and even signal-to-noise ratio (S/N) are better than analog, the design of its phase-locked loop (PLL) so that the output signal is not only the frequency is accurate, but also the phase jitter (Phase Jitter) and frequency drift can reach a fairly stable state, but after all, it is a digital source of digital circuits, digital circuits, and analog circuits, interference between the two, it is always difficult to effectively overcome. It is always difficult to effectively overcome, but also cause the small signal output is not as good as the analog function signal generator.

Talking about analog function signal source, the structure is as follows:

This is the structure of the universal analog function signal generator, is based on triangular wave generator circuit by the diodes constitute a sine wave rectifier circuit to generate a sine wave, and at the same time by the comparison of the comparator to generate a square wave.

And how the triangle wave is generated, the formula is as follows:

In other words, if a constant current source is used to charge the capacitor, a positive slope ramp wave can be generated. Similarly, right to a constant current source will be stored in the capacitor charge discharge that produces a negative slope of the ramp, the circuit structure is as follows:

When I1 = I2, you can produce a symmetrical triangular wave, if the I1 > > I2, at this time, that is, to produce a negative slope of the sawtooth wave, similarly, the I1 < < I2 that is, to produce a positive slope of the sawtooth wave.

Then, as shown in Figure 2, the selection of switch SW1 allows the charging rate to be changed by a multiple, that is, to change the frequency of the signal, which is the frequency gear selection switch on the panel of the signal source. The same synchronized change I1 and I2, can also change the frequency, which is the signal source to adjust the frequency of the potentiometer, but the need to simply convert the original voltage signal into current only.

And in the duty cycle adjustment on the design of the following two ideas:

1, the frequency (period) is unchanged, the pulse width changes, the method is as follows:

Changing the amplitude of the level, that is, change the reference amplitude of the comparator of the square-wave generator circuit, you can change the pulse width and the frequency of unchanged characteristics, but the main drawback is that the duty cycle can not be adjusted to less than 20%, resulting in the sampling circuit experiments. Resulting in sampling circuit experiments, the instantaneous signal collected by the signal changes, if the signal is used for analog-to-digital (A/D) conversion, then the digital signal changes and nothing to do. However, it is undeniable that the use of a better tune.

2, the duty cycle changes, the frequency follows the change, the method is as follows:

The reference amplitude of the square wave generator circuit comparator to be fixed (positive and negative can be switched using the circuit), change the slope of the charge and discharge, can be achieved.

This way of designing the general user response is "difficult to adjust", which is a major drawback, but it can produce less than 10% duty cycle is a necessary condition in the sampling.

The above two duty-cycle adjustment circuit design ideas have their own advantages and disadvantages, which of course also affects whether or not you can generate a "decent" sawtooth wave.

The next step is the design of the PA (Power Amplifier). First of all, the use of operational amplifiers (OP), and then the use of push-pull (push-pull) amplifiers (pay attention to the prevention of cross-distortion Cross-distortion) will be sent to the attenuation of the signal network, this part of the signal involved in the output of the signal source indicators, including signal-to-noise ratio, the rise time of the square wave and the frequency response of the signal source, a good source of course, is the sine wave of a high signal-to-noise ratio, the square wave of fast rise time, the triangular wave of linearity, and the frequency response, of course, is a good source. A good signal source is of course a sine wave with a high signal-to-noise ratio, a fast rise time, a triangular wave with good linearity, and a good volts frequency characteristics, (i.e., the frequency rises, the signal can not be attenuated or can not be reduced too much), this part of the circuit is more complex, especially at high frequencies, in addition to the use of capacitors for frequency compensation, it also involves the wiring of the PC board, one is not careful, it is very easy to cause oscillations, and would like to design this part of the circuit, in addition to the original analog theoretical foundations, but also need to have the experience of the actual. "In addition, it is also possible to use the same processor as the PC boards, so that the PC boards can be configured in a more efficient manner.

After the PA signal, through the π-type resistive attenuation network, respectively, attenuation 10 times (20dB) or 100 times (40dB), at this time a basic function waveform generator has been completed. (Note: the choice of π-type attenuation network instead of voltage divider circuit is to keep the output impedance of a certain).

A strong function waveform generator, there are sweep, VCG, TTL, TRIG, GATE and frequency meter functions, the design of which is also mentioned in passing:

1. Sweep: Generally divided into linear (Lin) and logarithmic (Log) sweep;

2. VCG: That is, the general FM, the input of an audio signal, you can generate the frequency modulation of the signal source itself. VCG: i.e. general FM, the input of an audio signal can generate frequency modulation with the signal of the signal source itself;

In the above two design modes, the first one should generate sawtooth and logarithmic signals, and the input signal of the second one is selected by the multiplexer, and then go through the voltage-to-current converter circuit to synchronize and add them to the I1 and I2 in Fig. 2;

3. TTL Synchronous Output: The square wave is converted into a square wave by the transistor circuit, and then synchronized into a square wave by the triode circuit. square wave through the transistor circuit into 0 (Low), 5V (High) TTL signal can be.

But note that such a TTL signal has to go through a buffer gate to increase the number of fan-outs (Fan Out), and usually a few buffers are connected in parallel, while the TTL INV just needs to be added with a NOT Gate;

4. TRIG Function: Similar to the One Shot function, inputting a TTL signal allows the signal source to generate one cycle of the signal. The signal source can produce a cycle of the signal output, the design is in the absence of signal input, the figure two SWI ground can be;

5. Gate function: that is, the input of a TTL signal, so that the signal source in the input for the Hi, the generation of waveforms output, until the input for the LOW, the figure two SWI ground and turn off the signal source output;

6. Frequency meter: in addition to the simple dial on the market. In addition to the simple dial display on the market, whether it is a LED digital tube or LCD liquid crystal display frequency, and its frequency meter circuit is overlapped, the block diagram is as follows:

2. Arbitrary Waveform Generator, the best instrument for simulation experiments

Arbitrary Waveform Generator is a type of signal source, which has all the characteristics of the signal source. We traditionally think that a signal source is mainly used to provide known signals (various waveforms) to the circuit under test, and then other instruments are used to measure the parameters of interest. Visible signal source in electronic experiments and test processing, and does not measure any parameters but according to the user's requirements, the simulation of a variety of test signals, provided to the circuit under test, in order to achieve the needs of the test.

There are many kinds of signal sources, including sine wave signal source, function generator, pulse generator, scanning generator, arbitrary waveform generator, synthesized signal source and so on. Generally speaking, an arbitrary waveform generator is a special signal source, which has the ability to generate waveforms from other signal sources, and thus is suitable for a variety of simulation experiments.

First, the function of the function, the simulation of the basic laboratory designer environment

Function signal source is the most widely used general-purpose signal source, which can provide a sine wave, sawtooth wave, square wave, burst waveforms, and so on, and some also have the ability to modulate and scanning at the same time, it is known that in our basic experiments (such as the university electronics labs, scientific research laboratories, factories to develop the lab) It is well known that in our basic experiments (e.g. university electronics labs, research labs in scientific research, factory development labs, etc.), we design a circuit and need to verify its reliability and stability, so we need to apply an ideal waveform to it in order to identify the authenticity. Such as we can use the DC compensation function of the signal source to control the DC bias level of solid-state circuits; we can be suspected of a faulty digital circuit, the use of the signal source's square wave output as a digital circuit clock, while the use of a square wave plus DC compensation to produce an effective logic level analog output, to observe the circuit's operating conditions, and to confirm the faulty defects of the place. In short, the use of arbitrary waveform generators in this area of the basic functions, can simulate the signal necessary for your basic laboratory.

Second, arbitrary waveforms, simulating more complex signal requirements

As we all know, in our actual electronic environment designed by the circuit in operation, due to a variety of interferences and responses to the presence of actual circuits there are often a variety of signal defects and transient signals, such as overpulsing, spiking, damping transients, sudden changes in frequency, etc. (see Figure 1, Figure 2), the occurrence of these situations, such as at the beginning of the design is not taken into account, there are a variety of signal defects. Some of these occurrences, if not taken into account at the beginning of the design, will have disastrous consequences. For example, the overshooting pulse at a in Fig. 1, if given to a circuit with poor impulse resistance, could cause the entire device to "burn out". Recognizing the degree of sensitivity of the circuit to such a situation, we can avoid unnecessary losses, this aspect of the requirements in the aerospace, military, railroads and some of the more complex and important areas of the situation is particularly important.

Due to the special features of the arbitrary waveform generator, in order to enhance the ability to generate arbitrary waveforms, it often relies on computer communications output waveform data. In the computer transmission, through the dedicated waveform editing software to generate waveforms, is conducive to expanding the capacity of the instrument, and further simulation simulation experiments. At the same time, due to edit an arbitrary waveform sometimes need to spend a lot of time and energy, and each time the waveform editing may vary so that some arbitrary waveform generator, built-in a certain amount of non-volatile memory, random access to edit the waveform, is conducive to the reference and comparison; or through a random interface communication transmission to the computer for further analysis and processing.

Third, download and transfer, further real-time simulation

In some military, aviation, transportation manufacturing and other fields, some circuits are difficult to estimate the operating environment, after the completion of the experimental design, in the real environment need to make further experiments, some of the experiments are very costly or risky (such as high-speed experiments on the train track changes, the aircraft test run propeller operation), it is not possible to long time. (such as high-speed train experiments when the rail changes, aircraft test run when the propeller, etc.), it is not possible for people to experiment for a long time to determine the feasibility and stability of the designed product (such as high-speed trains, airplanes), etc.; we can use some of the arbitrary waveform generator waveform download function, in the case of some of the troublesome costly or risky experiments, the waveforms through the digital oscilloscope and other instruments to record the waveforms in real time, and then through the computer interface to the source of the signal, downloaded directly to the design circuit, further experiments to verify that. The newest addition to the lineup is a new, more robust, and more robust design.

In summary, an arbitrary waveform generator is the best tool for signal simulation experiments for electronic engineers. In addition to the shortcomings of traditional signal sources - frequency accuracy, frequency stability, amplitude accuracy, signal distortion, we should be more concerned about its editing and waveform survival and download capabilities, but also pay attention to the number of channels of its output in order to synchronize the comparison of the two signals of the phase shift characteristics of the further to achieve the experimental state of the simulation.