I think, I already described a possible circuit in post #5. 4 transistors required, single transistor switches for +5 and -5, dual transistor in series circuit for the ground switch.
The premise of needing threefold switch for sign-magnitude isn't plausible to me, however. Why not using a regular ladder with double-throw switches after re-encoding the control word?
I'm referring to a structure like below
View attachment 142816
As previously mentioned, I wonder if the discrete MOSFET design can achieve reasonable performance in a regular DAC application. At least the useful speed will be very low due to charge injection.
The control of the four-quadrant switch must be referenced to its source.But how to control M1/M2?
The control of the four-quadrant switch must be referenced to its source.
So far, Ctrl+/- was referenced to ground. Ctrl0 must be referenced to the source of M1/M2.
M1 and M2 are both NMOS. Reconsider reviewing schematic.Also if I tie M2 gate to +5V and M1 gate to -5V I get 1.86V at the output and 928 mV at M1/M2 source. In this case NMOS M1 Vgs is around -4V and PMOS M2 Vgs is around +4V.
What issue?
Use the 0 to +5V to control M1/M2.
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