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@ericfont

ericfont/circuit-20251129-2331.svg

Created November 30, 2025 04:29
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try delta mod with multiple lowpass upfront
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ericfont commented Nov 30, 2025

sim

oscilates around 150kHz.

better than 100 dB SNR ideally at least:

image

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ericfont commented Nov 30, 2025

now try with 3 lowpasses...lowers oscillation to 85kHz:

circuit-20251129-2335

image

Not sure if that helped. The 30kHz harmonic is more pronounced now, as the oscillation frequency is lowered.

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ericfont commented Nov 30, 2025

try no input

glitchy:

image

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ericfont commented Nov 30, 2025

single lowpass ~15.9kHz, oscillate around 300kHz, seems pretty good:

image

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ericfont commented Nov 30, 2025

image image

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ericfont commented Nov 30, 2025

If assume 1MHz GBWP opamp, then the 0degrees intersect is ~135 KHz.

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ericfont commented Nov 30, 2025

fine to add 10Mohm feedback resistor to remove <20Hz

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