Oscillation composed of op amp and passive crystal oscillator

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Oscillation composed of op amp and passive crystal oscillator [Copy link]

1. Gate circuit plus passive crystal oscillator can form an oscillation circuit, and the frequency can reach M level. 2. Wien bridge can generate a sine wave oscillation circuit, but the frequency is usually at K level. Now I want to change the Wien bridge to use a passive crystal oscillator plus an op amp to form an oscillation. I don’t know if it can achieve a frequency of the passive crystal oscillator within 5M~20M. The gain bandwidth and slew rate of the selected op amp are large enough. I found a circuit on the Internet, but I don’t know how to analyze it. Please help me take a look, or provide other circuit solutions.

wsmysyn

Do you want to use the sine wave with accurate frequency from the crystal oscillator? ? I have used SN74lvc1404 with 24MHz crystal before, and successfully drove it. The output at the Xout end was a very good 24MHz sine wave, and it can also output a 24MHz square wave. . The principle is very simple. There are two inverters in the chip. You can drive it yourself with two inverters using the Pierce oscillator principle.

maychang

Now I want to change the Wien bridge to a passive crystal oscillator plus an op amp to form an oscillation. I don't know if it can be realized. After the Wien bridge oscillation circuit is changed, it is no longer a Wien bridge, so there is no talk of changing the Wien bridge. Of course, a quartz crystal plus an op amp can form an oscillator, but it also needs to meet the conditions for generating oscillation.

maychang

I found a circuit on the Internet, but I don't know how to analyze it. I don't need to analyze it anymore. It's a wrong circuit, so why analyze it?

maychang

wsmysyn posted on 2018-6-22 09:44 Do you want to use the sine wave with accurate frequency from the crystal oscillator? ? I have used SN74lvc1404 plus 24MHz crystal before and successfully drove it. In Xo ...

SN74lvc1404 is a chip specially designed as a crystal oscillator. It does have two inverters. But to make the crystal oscillate, only one of the inverters is used. If you use the inverter and crystal to oscillate yourself, one inverter is enough, and you don't have to use two.

maychang

It is possible to use an op amp to construct a quartz crystal oscillator, but it is definitely not cost-effective. Digital circuit chips are cheaper than op amps, and an inverter plus two small capacitors and a quartz crystal can be used.

wsmysyn

maychang posted on 2018-6-22 10:35 SN74lvc1404 is a chip specially designed as a crystal oscillator. It does have two inverters. But to make the crystal oscillate, only one of them is used...

Yes, yes. This problem seems to have been encountered two years ago. This chip was used at that time and is still in use now. . A relatively simple way to generate a 24M sine wave is used in a factory environment and is relatively easy to maintain.

chunyang

There is no such thing as a "passive crystal oscillator". Crystal oscillator is the abbreviation of crystal oscillator, which must be an active composite device. Passive ones are not called crystal oscillators but crystals. Technicians should be rigorous. Regarding the crystal oscillator circuit, as maychang said, it is simplest and cheap to build a crystal oscillator circuit yourself using logic gates. The operational amplifier has no advantages under the working conditions of the crystal oscillator circuit, but the disadvantages are prominent. Even if you want to obtain high-order harmonics, there are better solutions. For the baseband crystal oscillator circuit, use an inverter.