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The gain of a DAC in the current mode configuration may be adjusted by a series resistor in the reference port. In the current mode, the end of the ladder, with its code-independent impedance, is used as the Vref terminal, and the ends of the arms are switched between ground and an output line which must be held at ground potential (or, in HF DACs, between differential output lines at ground potential). The normal connection of a current mode ladder network output is to an op-amp configured as an I-V converter, but stabilization of this op-amp is complicated by the DAC output impedance variation with code. Current mode operation has higher glitches though, since the switches connect directly to the output line, but as the switches of a current-mode ladder network are always at ground potential, the design of such a switch is less demanding and, in particular, their voltage rating does not affect the reference voltage rating. If switches capable of carrying current in either direction (such as MOS devices) are used, the reference voltage may have either polarity, or may even be AC. Such a CMOS structure is one of the most common types of multiplying DAC (MDAC).
