AD1853: output impedance

Q

Output impedance of AD1853 current output audio DAC
The data sheet for AD1853 specify a couple of things for the analog
outputs, but not the output impedance (it specifies output capacitance).
Would it be possible to obtain that information?

A

Normally the output impedance of the AD1853 is so high that it can be neglected
and the current output DAC simply looks like a current source. To reach the
specified performance the AD1853 should drive an op-amp I to V converter, as
shown in figure 29 and 30. By driving the virtual earth at the -ve terminal of
the op-amp, the DAC is looking into a very low impedance because the voltage at
the virtual earth hardly changes over the output current range of the DAC.

For some other type of load e.g. a passive load referred to ground, the voltage
at the DAC outputs changes with output current, which causes the specifications
to be degraded, and therefore the I to V converter is the recommended load.

Also, please ignore the section entiltled Output Drive, Buffering and Loading.
this is a datasheet error and refers to a DAC with voltage output, not current
output.

If you are looking for a DAC with a voltage output, you might wish to consider
the AD1852.

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