..I raise you with a single-node servo cct, attached...

/Jakob E.

Interesting...

What's the benefit VS a conventional DC servo?

What about stability?


abbey road d enfer

Interesting...

What's the benefit VS a conventional DC servo?

What about stability?
That's an interesting trick. Stability is unquestionable since it involves only one opamp.
Main drawbacks is limited capability; this wouldn't work with a power amp. Here it works because the opamp needs delivering only a small current (1mA to correct 47mV offset), but in a power amp it would need to be capable of delivering amps.
Even using it to servo a DOA wouldn't work. The typical output Z is about 0.01 ohm. Correcting 1mV of offset requires injecting 100mA. The output impedance must be artificially increased by adding a series resistor, which is not what you want when driving a transformer.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

..I raise you with a single-node servo cct, attached...

/Jakob E.

Yep, thanks  :)
Note to self:  Don't let c**ts wind you up

clintrubber

Operating in the digital domain with some rudimentary logic (maybe a small microprocessor) you can use the output of the ADC itself to perform a self calibration with input (shorted). Using digital pots you can correct a decent range of DC offset errors. This will be fine for relatively short term measurements, but long term stability has other variables, like temperature coefficient of components and even devices.

Not necessarily shorting inputs, digital implementation (at least as in my patent) can operate in the presence of signal.
As said, in essence it's a digital implementation of a DC-servo. (Whether that's suited for the circuit of TS is another thing.)
 
FWIW, auto-zeroing (for the balanced circuit as was the DUT for the patent) can elegantly be done by a cross-switch before the ADC, and 'correcting' in the SigmaDelta-bitstream by simply inverting the bitstream. (Think of it as reversing up/down-counting when the analog cross-switch is in cross-position.)



 

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