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The MEMS oscillator topology i simulate is below enter image description here

fig1: Oscillator schematic Source: A Tunable-Gain Transimpedance Amplifier for CMOS-MEMS Resonators Characterization

Below is mine, the resonator i am using is around 520 [kHz]

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fig2: LTSpice simulation command

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fig3: Oscillator circuit with MEMS equavilent model, sustaining amplifier, and a pulse to start oscillate

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fig4: Vo

But the output (Vo) is not showing any sign for oscillatung.

In the best of my knowledge, the sustaining amplifier must have a gain greater than rm of resonator in [dBohn] and a phase shift of 0 [deg] which from my below is also meet enter image description here

fig5: Sustaining amplifier or so called TIA simulation circuit

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fig5: Sustaining amplifier or so called TIA simulation result

Could someone point out where im doing wrong?

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  • \$\begingroup\$ You have the output shorted to ground... that op-amp isn't happy. Not that SPICE simulates smoke ;) \$\endgroup\$ Aug 25, 2023 at 4:28
  • \$\begingroup\$ @TimWilliams Sorry, could you point out how to apply your advice to the circuit? \$\endgroup\$
    – Jack Huang
    Aug 25, 2023 at 5:12
  • \$\begingroup\$ In fig.3, V3 defines Vo. \$\endgroup\$ Aug 25, 2023 at 6:11
  • \$\begingroup\$ @TimWilliams I see, Is there any suggestion where i could place the impulse to start the circuit? \$\endgroup\$
    – Jack Huang
    Aug 25, 2023 at 6:31
  • \$\begingroup\$ In series, or as a current to any other node, would likely work. \$\endgroup\$ Aug 25, 2023 at 8:36

1 Answer 1

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The loop should include an inverting gain stage. A positive feedback is required for oscillations.

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  • \$\begingroup\$ Thank you for your reply. The problem was solved, I figured out that my circuit doesnt fullfill the barkhausen criteria. \$\endgroup\$
    – Jack Huang
    Oct 15, 2023 at 15:22

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