Looking for a 1-bit DAC schematic

[cjupiter]

Searching for a 1-bit DAC schematic to use in the design of a swtiched capacitor SIGMA-DELTA ADC. I know that a 1-bit DAC DAC is simply a switch that connects the negative input of the difference amplifier to a positive or a negative reference voltage. I just need a point in the right direction.

Cheers for any help

 

[uladz55]

1-bit dac

1-bit DAC is two switches combined together.
Connect inputs of two complementary switches (schematic see in Razzavi Design of Analog CMOS IC, ch.12, p.410-423) to the input of Integrator.
Two outputs of these switches connect to positive and negative reference voltage appropriately.

 

[cjupiter]

1bit dac

thanks uladz55

Unfortunately that book you are referring to is loaned out at my university's library. I imagine that you could be referring to something similar to a CMOS inverter. This will switch between rails depending on the logic input. I have simulated this circuit in Spice but the only problem is, if i input a logic signal between 0 and 1.8V, the output of the inverter will remain at the positive rail (i chose rails +-0.5V) and will not switch to the negative rail. I can fix this by inputting a logic signal ranging from -1.8 to +1.8, but i rather not since the output of my comparator is either 0 or +1.8V. Any ideas?

-Con

 

[cjupiter]

dac schematic

here is my schematic

 

[uladz55]

1 bit dac schematic

connect to negative or positive Vref means to connect Vref to negative or positive integrator input.
Vref is positive.

 

[uladz55]

dac schematics

ur schematic is wrong.

see Razavi book

**broken link removed**

 

[cjupiter]

1 bit dac circuit

ive downloaded that book, which question am i looking at, is it in chapter 12?

Thanks

 

[uladz55]

schematic dac

excuse me, it's lRazavi book's problem solutions.

The book is here