How does a transmission gate multiplexer select and pass a single signal from multiple inputs?
1 Answer
A transmission gate multiplexer (also known as an analog switch or bilateral switch) is a digital circuit that allows one of several input signals to pass through to an output based on the control signal. It acts like a mechanical switch, connecting or disconnecting various inputs to the output.
The transmission gate multiplexer typically consists of transmission gate elements (also known as pass gates or bilateral switches). Each transmission gate is a combination of a complementary pair of MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), one P-channel and one N-channel. The gates of these transistors are controlled by the same control signal.
Here's how a transmission gate multiplexer selects and passes a single signal from multiple inputs:
Transmission Gate Structure: Each input signal is connected to the sources or drains of the MOSFET pair in the transmission gate. The control signal controls the gates of both MOSFETs simultaneously.
Control Signal: The control signal is usually a digital signal (0 or 1) that determines which transmission gate is "closed" (ON) and which ones are "open" (OFF). When the control signal is at logic 0 (or ground), the N-channel MOSFET is OFF, and the P-channel MOSFET is ON. Conversely, when the control signal is at logic 1 (or high voltage), the N-channel MOSFET is ON, and the P-channel MOSFET is OFF.
Passing the Selected Signal: When the control signal is at logic 0, the N-channel MOSFET conducts, allowing the signal connected to its source or drain to pass through to the output (connected to the drain or source of the P-channel MOSFET). At the same time, all other transmission gates have their N-channel MOSFET OFF, preventing the signals from those inputs from reaching the output.
Blocking Non-Selected Signals: Conversely, when the control signal is at logic 1, the N-channel MOSFET is OFF, and the P-channel MOSFET is ON, allowing the signal connected to the P-channel MOSFET's source or drain to pass through to the output. This action blocks all other signals connected to the transmission gates with their N-channel MOSFET ON from reaching the output.
By controlling the state of the control signal, the transmission gate multiplexer effectively selects and passes only the signal from the desired input to the output, while isolating all other inputs.
It's important to note that transmission gate multiplexers are commonly used in analog circuits to switch analog signals rather than digital signals, as they can maintain the integrity of the analog signal with minimal distortion. However, they can also be used in digital applications when required.
The transmission gate multiplexer typically consists of transmission gate elements (also known as pass gates or bilateral switches). Each transmission gate is a combination of a complementary pair of MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), one P-channel and one N-channel. The gates of these transistors are controlled by the same control signal.
Here's how a transmission gate multiplexer selects and passes a single signal from multiple inputs:
Transmission Gate Structure: Each input signal is connected to the sources or drains of the MOSFET pair in the transmission gate. The control signal controls the gates of both MOSFETs simultaneously.
Control Signal: The control signal is usually a digital signal (0 or 1) that determines which transmission gate is "closed" (ON) and which ones are "open" (OFF). When the control signal is at logic 0 (or ground), the N-channel MOSFET is OFF, and the P-channel MOSFET is ON. Conversely, when the control signal is at logic 1 (or high voltage), the N-channel MOSFET is ON, and the P-channel MOSFET is OFF.
Passing the Selected Signal: When the control signal is at logic 0, the N-channel MOSFET conducts, allowing the signal connected to its source or drain to pass through to the output (connected to the drain or source of the P-channel MOSFET). At the same time, all other transmission gates have their N-channel MOSFET OFF, preventing the signals from those inputs from reaching the output.
Blocking Non-Selected Signals: Conversely, when the control signal is at logic 1, the N-channel MOSFET is OFF, and the P-channel MOSFET is ON, allowing the signal connected to the P-channel MOSFET's source or drain to pass through to the output. This action blocks all other signals connected to the transmission gates with their N-channel MOSFET ON from reaching the output.
By controlling the state of the control signal, the transmission gate multiplexer effectively selects and passes only the signal from the desired input to the output, while isolating all other inputs.
It's important to note that transmission gate multiplexers are commonly used in analog circuits to switch analog signals rather than digital signals, as they can maintain the integrity of the analog signal with minimal distortion. However, they can also be used in digital applications when required.