Crystal load and oscillator margin
Equal load capacitors, critical transconductance, gain margin and crystal drive estimate.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Model: C1=C2=2(CL−Cstray); gmcrit=4 ESR(2πf)²(C0+CL)²; margin=gm/gmcrit; drive=Irms² ESR
Assumptions
- Small-signal Pierce-oscillator screening model with equal external capacitors. The entered gm must be actual oscillator transconductance, not a device parameter named maximum critical gm.
- Crystal current must be motional RMS current. Startup and drive require device/circuit verification.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Crystal frequency
- 8000000 Hz
- Specified load capacitance
- 1e-11 F
- Equivalent stray load capacitance
- 3e-12 F
- Crystal shunt capacitance C0
- 7e-12 F
- Crystal motional ESR
- 80 Ω
- Oscillator transconductance
- 0.025 S
- Crystal motional RMS current
- 0.0001 A
- Manufacturer maximum drive power
- 0.0001 W
Results
- Each external load capacitor
- 1.4e-11 F
- Gain margin
- 106.992
- Critical transconductance
- 0.000233662 S
- Estimated crystal drive power
- 8e-7 W