A powerful function waveform generator with sweep, VCG, TTL, TRIG, GATE, or LCD liquid crystal display frequency that overlaps with the frequency meter circuit
The minimum output signal can be less than 1mV, leading domestically. The high power function signal generator was once the first in China. Stability, high reliability, low price performance Features unique output protection technology in China, can effectively prevent overload, output short circuit, misconnection and other misoperations or external current backflow damage. Technical indicators output signals: triangle wave, square wave, sine wave, pulse wave, single pulse. TTL level, DC level voltage output output amplitude 1mV-25Vp-p Output impedance: 50Ω±10% 3-digit display output frequency: 0.2 Hz-2MHz Frequency error: ±1% 4-digit display power output frequency 0.2Hz -200KHz Output power ≥10W No-load voltage: ≥25Vp-p External measurement frequency: 0.1Hz-10MHz ±0.1% Attenuation: 0dB, -20dB, -40dB, –60dB DC level: +10V--10V continuously adjustable duty cycle: 10%-90% continuous adjustable distortion: ≤2% (20Hz-20kHz) square wave rise time: ≤50nSTTL square wave output: ≥3Vp-p rise time ≤25ns external voltage control sweep frequency: input level 0-10V output frequency 1:100 power supply: 220V ±10% 50Hz-60Hz Dimensions: 240 (W) × 90 (H) × 280 (D ) Weight: Approx. 2.5Kg output adopts the latest protection circuit at home and abroad.
(1) Function generator composed of discrete components: usually a single function generator and the frequency is not high, its operation is not very stable, it is not easy to debug
(2) It can be fabricated by general-purpose devices such as transistors and op amp ICs, and more often by a special function signal generator IC. Early function signal generator ICs, such as L8038, BA205, XR2207/2209, etc., have fewer functions, less precision, and the upper frequency limit is only 300 kHz, which cannot generate higher frequency signals, and the adjustment method is not flexible enough. The air ratio cannot be adjusted independently, and the two affect each other.
(3) Function generator using monolithic integrated chip: It can generate multiple waveforms, achieve higher frequency, and is easy to debug. In view of this, the US company has developed a new generation of function signal generator ICMAX038, which overcomes the shortcomings of the chip in (2) and can achieve higher technical specifications, which is beyond the reach of the above chips. The MAX038 has a high frequency and high accuracy, so it is called a high-frequency precision function signal generator IC. The MAX038 is the preferred device for the design of circuits such as phase-locked loops, voltage-controlled oscillators, frequency synthesizers, and pulse width modulators.
(4) Function generator using a dedicated direct digital synthesis DDS chip: capable of generating arbitrary waveforms and achieving high frequencies. But the cost is higher.
An electrical test signal instrument that produces the required parameters. According to its signal waveform, it is divided into four categories: 1 sinusoidal signal generator. Mainly used to measure the frequency characteristics, nonlinear distortion, gain and sensitivity of circuits and systems. According to its different performances and uses, it can be subdivided into low frequency (20 Hz to 10 MHz) signal generator, high frequency (100 kHz to 300 MHz) signal generator, microwave signal generator, frequency sweep and program control signal generator. Frequency synthesis type signal generator, etc. 2 function (waveform) signal generator. It can generate certain periodic time function waveforms (sine, square, triangle, sawtooth, pulse, etc.) with frequencies ranging from a few microhertz to tens of megahertz. In addition to testing for communications, instrumentation and automatic control systems, it is also widely used in other non-electrical measurement fields. 3 pulse signal generator. A generator that produces rectangular pulses of adjustable width, amplitude, and repetition rate that can be used to test the transient response of a linear system or as an analog signal to test the performance of radar, multi-channel communication, and other pulsed digital systems. 4 random signal generator. It is usually divided into two types: noise signal generator and pseudo-random signal generator. The main purpose of the noise signal generator is to introduce a random signal into the system to be tested to simulate the noise in the actual working conditions to determine the system performance; plus a known noise signal compared with the internal noise of the system to determine the noise figure; Instead of sinusoidal or pulsed signals, system dynamics and the like are determined. When the correlation function is measured with a noise signal, if the average measurement time is not long enough, a statistical error will occur, which can be solved by a pseudo-random signal.
Generator
The signal generator is generally divided into a function signal generator and an arbitrary waveform generator, and the function waveform generator is designed to distinguish between analog and digital synthesis. It is well known that the digital synthesis function signal source is better than analog in terms of frequency, amplitude and even the signal-to-noise ratio (S/N) of the signal. The design of the phase-locked loop (PLL) makes the output signal not only frequency accurate but also phase jitter ( Phase Jitter) and frequency drift can reach a fairly stable state, but after all, it is a digital signal source. The interference between digital circuits and analog circuits is always difficult to overcome effectively, and it is also inferior to the analog function on the output of small signals. Signal generator.
Talking about the analog function signal source, the structure diagram is as follows:
This is a general analog function signal generator structure. A sine wave shaping circuit formed by a diode based on a triangular wave generating circuit generates a sine wave, and a square wave is generated by comparison of the comparator.
And how the triangle wave is generated, the formula is as follows:
In other words, if the capacitor is charged with a constant current source, a ramp with a positive slope can be generated. Similarly, the right-charge current discharges the charge stored on the capacitor to generate a ramp with a negative slope. The circuit structure is as follows:
When I1 = I2, a symmetric triangular wave can be generated. If I1 > >I2, a sawtooth wave with a negative slope is generated at this time. Similarly, I1 < < I2 produces a positive slope sawtooth wave.
As shown in Fig. 2, the selection of the switch SW1 can change the charging speed in multiples, that is, change the frequency of the signal, which is the selection switch of the frequency file on the signal source panel. Similarly, changing I1 and I2 synchronously can also change the frequency, which is the potentiometer for adjusting the frequency on the signal source, but simply convert the voltage signal into a current.
The design of the duty cycle adjustment has the following two ideas:
1. The frequency (cycle) is unchanged and the pulse width is changed. The method is as follows:
Changing the amplitude of the level, that is, changing the reference amplitude of the square wave generating circuit comparator, can achieve the characteristics of changing the pulse width and the frequency constant, but its main disadvantage is that the duty ratio cannot be adjusted to 20 [%]. In the following, the signal collected by the transient signal is changed during the sampling circuit experiment. If the signal is to be used for analog-to-digital (A/D) conversion, the obtained digital signal changes and is not suitable. But it is undeniable that it is better to use.
2. The duty cycle changes and the frequency changes. The method is as follows:
The reference amplitude of the square wave generating circuit comparator is fixed (positive and negative can be switched by the circuit), and the charging and discharging slope can be changed. [NextPage]
The design of this method is generally "difficult to adjust", which is a big drawback, but it can produce a duty cycle of less than 10 [%] but is a prerequisite for sampling.
The above two types of duty cycle adjustment circuit design ideas have their own advantages and disadvantages. Of course, the associated effects also affect whether a "decent" sawtooth wave can be produced.
Next, the design of the PA (power amplifier). The first is to use an operational amplifier (OP), and then use a push-pull amplifier (note the prevention of Cross-distortion) to send the signal to the attenuation network. This part involves the indicator of the signal output signal, including Signal-to-noise ratio, square wave rise time and frequency response of the signal source. A good signal source is of course a high sinusoidal signal-to-noise ratio, a fast square wave rise time, a good triangular wave linearity, and a good volt-frequency characteristic (ie, frequency). Rising, the signal can not be attenuated or can not be reduced too much), this part of the circuit is more complicated, especially in the high frequency, in addition to the use of capacitors for frequency compensation, but also involves the PC board wiring, accidentally, easily cause oscillation, think Designing this part of the circuit requires practical experience in addition to the original analog theory. The patience of "Try Error" is indispensable.
After the PA signal comes out, it is attenuated by 10 times (20dB) or 100 times (40dB) through a π-type resistive attenuation network. At this time, a basic function waveform generator is completed. (Note: Choosing a π-type attenuation network instead of a voltage divider circuit is to keep the output impedance constant)
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