Reduced-capacitance bus switch in isolated P-well shorted to source and drain during switching

摘要: A bus switch has reduced input capacitance. Parasitic source-to-well and drain-to-well capacitors are shorted by well-shorting transistors, eliminating these parasitic capacitances. The transistors turned on when the bus-switch transistor is on, but off isolates signals its source drain. isolated P-well under not tied to ground. Instead floating on. When off, underlying driven ground a biasing in another P-well. Since much lower doping than N+ drain, capacitance of well-to-substrate junction less Thus reduced, allowing higher frequency switching.