How to use the DAC output buffer from the ADuC706x as OP-AMP?
This can be done by setting bit 7 (OPAMP) of the DAC0CON MMR in the ADuC706x.With setting this bit the DAC-Buffer is configured as OP-AMP with its pin's available as shown in the picture below.
In addition the DAC can still be used if bit 6 (DACBUFBYPASS) in DAC0CON is set.But of course it is recommended to have a external Buffer for the DAC-output.Another application for this is to use the OP-AMP in combination withan external bipolar transistor to configure a 4-20mA loop withcurrent-regulation from the OP-AMP and set-point from the DAC.
We are using ADuC7061 DAC in a configuration similar to what you have mentioned in a 4-20mA driver. We have a kind of high performance modulated voltage source where an op-amp is used as an error amplifier, so that DAC output is connected to the op-amp positive input. If using DAC buffer op-amp it is important for us to know its characteristics like open-loop gain, unity-gain frequency and phase-margin plot. Could you provide such data?
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