# Tag Info

24

As said in the other answers, ceramic resonator oscillator circuits are extremely sensitive as they have high input impedance and huge gain. The bias resistance in the circuit is about 1 megaohm and the load capacitances are about 100 pF. Poking it with a finger that can have roughly 100 kohm and 10pF of impedance so will have a considerable effect on the ...

17

32kHz ultra low power oscillator: Used for RTCs (Real-time-clock). These can run in the background and enable time-keeping, even when the controller core is sleeping. This enables to have a running clock without the high power consumption of the controller core. The 32kHz oscillators are pretty precise and typically have an error of less than a minute per ...

16

The frequency of oscillation is determined by the 470 kΩ resistors and 3.3 μF capacitors and will be roughly $\frac 1 {RC} = \frac 1 {470k \times 3.3\mu} = 0.64 \ \text{Hz}$. i.e., less than one pulse per second. The circuit has been optimised for the LED rather than the speaker. Modify the circuit so that the frequency is 100 to 1000 times higher and you ...

10

What these are for: 32kHz low power: "digital watch" crystal. Use this when you want to power down the main oscillator but not lose track of what time it is so you can wake up periodically. 32kHz RC: cheaper (no crystal), but less accurate. When you want a digital watch that doesn't tell the correct time. external fast crystal: for things like ...

8

They are not strictly necessary but the vendor is attempting to cover as many use-cases with one part as they can. Some applications may want to use the internal oscillator, others may need a precise clock source, others may want low power consumption. Generally you will use only one in a specific design although in some cases the clock mode is changed ...

8

The OP-07 is a great little device but not suitable for your application. The signal coming from the 555 and LC filter is about 10 kHz and has an amplitude of about 14 volts peak-to-peak and the slow OP-07 just cannot keep up. It's output is slew rate limited to typically 0.3 volts per μs: - And that means a 14 volt change in output amplitude will take ...

7

You are correct that a capacitor "shifts phase for current, not voltage" or more accurately, the current in a capacitor is out of phase with the voltage. If the capcitor were ideal, the phase difference would be $90^{\circ}$. However, the phase shift network in an RC phase shift oscillator does not consist only of capacitors, but also resistors. ...

7

Ceramic resonators have overtone modes, like quartz crystals. Here's a picture, taken from this page by ECS. You can see the main mode, at about 455kHz, and a couple of other modes a bit above 1MHz. Generally, when your oscillator is running on the wrong mode, it's because you have too much gain at that other mode's frequency. In this case, you probably ...

6

Here is the clock configuration in block-diagram form from ST's configuration tool (STM32F103). As you can see, there are internal oscillators and two oscillators that use external frequency-determining components (crystals or resonators typically). I have this configured to use an external 8MHz crystal and a 32.768 kHz watch crystal. I could have used the ...

5

Your fingers are conductive, both resistivley and capacitivley. Resonator circuits tend to be high impedance types, so when you touch it you are adding parallel resistance and capacitance to the circuit. Thus you are inducing it to another frequency which it is able to maintain.

5

The oscillator you have is a multi-vibrator. It outputs a square wave. A square wave of low frequency sounds like a series of clicks when fed to a loud-speaker. At a higher frequency, as square wave sounds like a buzz. At even higher frequencies, it begins to have an "electronic music" type of sound.

3

The ATSAM family controllers typically have one really slow 32kHz oscillator used for low power applications, either with internal RC oscillator or external quartz crystal. And one high speed internal RC oscillator for "fast as it goes". In addition you can tweak around with PLL's, clock dividers and so on, and of course also provide external ...

3

I'm assuming you mean placing the series resistor as shown below: - Could you explain to my why 220 ohms is a good value? I've found suggestions of for instance 33 ohms elsewhere (also by the book of Ott. ) Where should it be located exactly and why? There will be resistance in the internal output from OSC_OUT and that may be enough to initiate ...

2

The purpose of the resistor is to reduce the drive power the crystal experiences. Too little drive power and the oscillator may not start reliably. Too much drive power and the crystal may age excessively or even fail. The optimum resistor (if any) is dependent on the maximum drive power specification of the particular crystal model and the ESR maximum of ...

1

An amplifier might be considered a voltage amplifier, whose input voltage provides an output voltage scaled by a unit-less "gain". In that case, "C" at amplifier output does nothing, and can be eliminated. Such an oscillator topology is not useful - at the resonant frequency of the remaining L & C, amplifier feedback has the wrong ...

1

You can use an LMC555/TLC555 or a microcontroller. The latter will be simpler and probably cheaper. The LMC555 is available in a fairly compact 1.5 x 1.5mm BGA package but requires more external components. You can only realistically get a few mA from a coin cell battery, which is just as well as you need to have the LED Vf very low. Modern LEDs can produce ...

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