High Threshold Logic

High Threshold Logic (HTL) is a variant of DTL which is used in such environments where noise is very high.

1 Operation
2 Advantages
3 Disadvantage
4 Usage
5 See also
6 References

Operation

The threshold values at the input to a logic gate determine whether a particular input is interpreted as a logic 0 or a logic 1.(e.g. anything less than 1 V is a logic 0 and anything above 3 V is a logic 1. In this example, the threshold values are 1V and 3V). HTL incorporates Zener diodes to create a large offset between logic 1 and logic 0 voltage levels.These devices usually ran off a 15 V power supply and were found in industrial control, where the high differential was intended to minimize the effect of noise.

Advantages

Increased Noise Margin
Spike Control
High Noise Threshold Value

Disadvantage

slow speed due to increased supply voltage resulting in use of high value resistors.

Usage

It is used extensively in industrial environments. e.g.

Logic Controllers with heavy noise
Heavy Process Machinery

References

Logic families

Technologies	BiCMOS · CMOS · Depletion-load NMOS logic (including HMOS) · Diode logic · Diode–transistor logic (DTL) · Direct-coupled transistor logic (DCTL) · Emitter-coupled logic (ECL) · Gunning transceiver logic (GTL) · Integrated injection logic (I²L) · NMOS logic · PMOS logic · Resistor–transistor logic (RTL) · Transistor–transistor logic (TTL)

Types	Static · Dynamic · Domino logic · Four-phase logic