Need help in understanding a circuit

Oct 16, 2007 2 Replies
K

Hi,



I'm relatively new to electronics and I'm trying to understand the following circuit:



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It's to control a laser galvanometer X/Y.



I see that a 12-bit DAC is being used to create the output voltages, but why are they then passed through an op-amp (TA75072) stage?



Also is the following multiplexer (TC74HC4053) only to provide "emergency off"?



What does the LM358 section do? It's tied to the inverting input of the TA75072, but I'm not sure why.



Finally, why does the section with the Schmitt triggers below this not seem to be connected to anything?



Thanks, Dave



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J

The DAC produces output voltage only between its reference input voltage and ground. The opamps offset the signal based on the reference voltage, so that the output is at zero volts when the DAC output is at half scale. So they convert the signal from Vref to ground range to +- 1/2 Vref range.

Can't say anything about emergencies, but it provides a choice of either the offset DAC output or ground.

It just buffers the voltage reference source, so that the gain divider loads from the two output opamps dies not shift the voltage.

They are the source of the negative supply voltage AVEE. They constitute a square wave oscillator and charge pump rectifier.

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K

Oh I get it...

Thanks - I couldn't think of a better term than "emergency off" :-)

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