# How can I determine the capacitance required for an oscillator (NOT A CRYSTAL!)?

In a typical clocking circuit configuration, where a crystal is tied at the input to an amplifier such as is shown below:

The capacitance required for $C_1$ and $C_2$ would be based on the load capacitance equation (sorry, not sure how to format equations on SE):

$$C_L = \frac{C_{1}\times C_{2}}{C_{1}+C_{2}}+C_S$$

However, what happens when you use an oscillator... such as the ACH-25.000MHZ-EK?

There is nothing in the application notes about needing a capacitor, so do I actually need one? (and for oscillators in general?) I am thinking that because this is still an oscillating circuit, similar to the crystal (clock configuration circuit)... That I will still need some sort of capacitor to keep the oscillator stable. Or am I wrong, and do I not need to attach any capacitor(s) to either the output or GND pins?

• You don't need a capacitor. This oscillator circuit is providing a clock signal out of the box (well, just power it...) – Eugene Sh. Feb 1 '18 at 15:28
• Additionally, having trouble viewing pictures I've pasted into my question... Not sure if others are having difficulties. – Snoop Feb 1 '18 at 15:28
• Ok @EugeneSh. but won't the rest of the circuit's capacitance, somehow have to factor into how the oscillator output should be stabilized? – Snoop Feb 1 '18 at 15:30
• @Snoopy: which CPU? datasheet! – Curd Feb 1 '18 at 15:33
• @Snoopy: but the AD9833 has only ONE clock input (no oscillator on chip, just a clock input); see also Evaluation Board Schematic in datasheet. So you question doesn't make sense. – Curd Feb 1 '18 at 15:48