Transmission gate

In principle, a transmission gate is made up of two field-effect transistors (FET), in which – in contrast to traditional discrete field-effect transistors – the substrate terminal (bulk) is not connected internally to the source terminal.

The gate terminal of the p-channel MOSFET is caused by the inverter, to the positive supply voltage potential.

When the control input is a logic one, the gate terminal of the n-channel MOSFETs is located at a positive supply voltage potential.

By the inverter, the gate terminal of the p-channel MOSFETs is now at a negative supply voltage potential.

A typical example in 4000-series and 74-series called the 4066 4-way "bilateral switch" can handle analog or digital signals and is available from various manufacturers.

[3][4][5] Logic circuits can be constructed with the aid of transmission gates instead of traditional CMOS pull-up and pull-down networks.

Principle diagram of a transmission gate. The control input ST must be able to take to control depending on the supply voltage and switching voltage different logic levels.
Two variants of the " bow tie " symbol commonly used to represent a transmission gate in circuit diagrams
Resistance characteristic of a transmission gate. VTHN and VTHP denote those positions at which the voltage to be switched has reached a potential, where the threshold voltage of the respective transistor is reached.