The basic operating principles of a sampling gates are illustrated in figures (a) and (b).
a) Series Switch.
b) Shunt Switch.
In figure (a) the switch is normally open, but is in closed position when the signal is transmitted.
In figure (b) the switch is normally closed, but is in open position when the signal is transmitted.
- These switches are normally electronic-devices diodes or transistors.
- When the device is conducting , it acts as a closed switch and when the device is not conducting, it acts as an open switch.
- Ideally a closed switch should have zero resistance and an open switch should have infinite resistance.
- But semiconductor devices do not have infinite back resistance and their forward resistances may lie in the range of several ohms.
- When such devices are used as switches, there is no specific advantages of either the series or the shunt switch position.
- The choice of the circuit depends upon the particular application.