how do i reduce the Power to the Crystal with an Resistor to the typical 100 uW mark?

[Scarlett133]

 

[FvM]

Don't expect that the circuit will oscillate with significant R3 resistance.

 

[Scarlett133]

Don't expect that the circuit will oscillate with significant R3 resistance.

Well do you maybe have an another solution in mind?

 

[FvM]

I doubt that a drive level as high as 100 uW will be ever reached in this circuit.

 

[FvM]

O.k., checked in simulation, as soon as base-collector junction becomes forward biased (voltage is clamped), crystal current rises above mA and power exceeds 100 uW level, Not easily to control.

 

[Scarlett133]

O.k., checked in simulation, as soon as base-collector junction becomes forward biased (voltage is clamped), crystal current rises above mA and power exceeds 100 uW level, Not easily to control.

Okay then ill think of an another Circuit, Thank you very much for your Help!

 

[dick_freebird]

I think you want to select C value, not add R,
to get the right forcing amplitude. R makes
low pass, C makes voltage divider w/ XTAL.

 

[Scarlett133]

I think you want to select C value, not add R,
to get the right forcing amplitude. R makes
low pass, C makes voltage divider w/ XTAL.

True i completely forgot about that! Thanks!

 

[timer32]

it turned out to be a simulation

 

[timer32]

it turned out with a 1.68k resistor

 

[FvM]

If I understand right, you are plotting output power, not crystal power absorption.

Problem of the circuit is, that oscillation magnitude and even capability to oscillate strongly depends on load impedance.

 

[vfone]

In 70's M.M.Driscoll proposed a very low phase noise crystal oscillator based on a cascode configuration.
The power across the crystal resonator is much lower compared to other configurations.

 

[Scarlett133]

it turned out with a 1.68k resistor

So this Config is working?

--- Updated Feb 1, 2025 ---

and will 1.8k work?

 

[dick_freebird]

A resistor anywhere in the tank-loop will
scrub away signal power, de-Q-ing. The
two caps you usually see to ground are
the rest of the circulating resonant current
loop. MOS gate capacitance becomes just
part of the tank C. BJT base impedance @
OP is a loss term that an amplifier has to
make up in addition to its other burdens.

 

[grun]

Are you sure that even the drivelevel is any problem? i built it without any resistor and its working fine sadly i cant measure it

 

[timer32]

Так эта конфигурация работает?

So does this configuration work?

--- Updated Feb 1, 2025 ---

Will 1.8k work? No

 

[BradtheRad]

Talking about a simulated crystal oscillator...
This topology is easy to draw, and to make adjustments.
The crystal is default 10MHz in Falstad's (based on RLC values which I can see in Edit window but which I did not touch). The op amp produces +4-4V bipolar. Resistor values were found by experimentation so that frequency settles around 10MHz. The crystal carries 800 µA. I'm not sure how much this simulation agrees with real-life nor am I sure which topology is easier to work with.

--- Updated Feb 2, 2025 ---

Link below runs schematic in Falstad's animated interactive simulator (at his website)...

tinyurl.com/2yjptwhy